Hydrogen Cyanide

H224: Extremely flammable liquid and vapor [Danger Flammable liquids]

H330: Fatal if inhaled [Danger Acute toxicity, inhalation]

H400: Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410: Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

P210, P233, P240, P241, P242, P243, P260, P271, P273, P280, P284, P303+P361+P353, P304+P340, P316, P320, P370+P378, P391, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement)

H300: Fatal if swallowed [Danger Acute toxicity, oral]

H310: Fatal in contact with skin [Danger Acute toxicity, dermal]

P260, P262, P264, P270, P271, P273, P280, P284, P301+P316, P302+P352, P304+P340, P316, P320, P321, P330, P361+P364, P391, P403+P233, P405, and P501 (click each P-code to see the statement)

H224 (84.6%): Extremely flammable liquid and vapor [Danger Flammable liquids]

H300+H310+H330 (14%): Fatal if swallowed, in contact with skin or if inhaled [Danger Acute toxicity, oral; acute toxicity, dermal; acute toxicity, inhalation]

H300 (93.3%): Fatal if swallowed [Danger Acute toxicity, oral]

H310 (93.3%): Fatal in contact with skin [Danger Acute toxicity, dermal]

H330 (100%): Fatal if inhaled [Danger Acute toxicity, inhalation]

H372 (41.9%): Causes damage to organs through prolonged or repeated exposure [Danger Specific target organ toxicity, repeated exposure]

H400 (100%): Very toxic to aquatic life [Warning Hazardous to the aquatic environment, acute hazard]

H410 (100%): Very toxic to aquatic life with long lasting effects [Warning Hazardous to the aquatic environment, long-term hazard]

P210, P233, P240, P241, P242, P243, P260, P262, P264, P270, P271, P273, P280, P284, P301+P316, P302+P352, P303+P361+P353, P304+P340, P316, P319, P320, P321, P330, P361+P364, P370+P378, P391, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 344 reports by companies from 9 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Information may vary between notifications depending on impurities, additives, and other factors. The percentage value in parenthesis indicates the notified classification ratio from companies that provide hazard codes. Only hazard codes with percentage values above 10% are shown. For more detailed information, please visit ECHA C&L website.

P273, P391, and P501 (click each P-code to see the statement)

H319: Causes serious eye irritation [Warning Serious eye damage/eye irritation]

H370: Causes damage to organs [Danger Specific target organ toxicity, single exposure]

H372: Causes damage to organs through prolonged or repeated exposure [Danger Specific target organ toxicity, repeated exposure]

P210, P233, P240, P241, P242, P243, P260, P262, P264, P264+P265, P270, P271, P280, P284, P301+P316, P302+P352, P303+P361+P353, P304+P340, P305+P351+P338, P308+P316, P316, P319, P320, P321, P330, P337+P317, P361+P364, P370+P378, P403+P233, P403+P235, P405, and P501 (click each P-code to see the statement)

Administration of oxygen may be needed. Fresh air, rest. Half-upright position. No mouth-to-mouth artificial respiration. Refer immediately for medical attention.

Wear protective gloves when administering first aid. Remove contaminated clothes. Rinse skin with plenty of water or shower. Refer immediately for medical attention.

First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then refer for medical attention.

Rinse mouth. Administration of oxygen may be needed. NO mouth-to-mouth artificial respiration. Do NOT induce vomiting. Refer immediately for medical attention.

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

Refer to the "General First Aid" section. Specific First Aid: For corrosives, in case of contact, immediately flush skin or eyes with running water for at least 30 minutes. Additional flushing may be required. (ERG, 2024)

Excerpt from ERG Guide 117 [Gases - Toxic - Flammable (Extreme Hazard); polymerization hazard]:

Refer to the "General First Aid" section. Specific First Aid: In case of contact with liquefied gas, only medical personnel should attempt thawing frosted parts. In case of burns, immediately cool affected skin for as long as possible with cold water. Do not remove clothing if adhering to skin. (ERG, 2024)

For information on chemical warfare blood agents see the ERG Criminal or Terrorist Use of CBR Agents. (ERG, 2024)

Warning: Hydrocyanic acid may be fatal if inhaled, swallowed, or absorbed through skin or mucous membranes. Caution is advised.

Signs and Symptoms of Acute Hydrocyanic Acid Exposure: Signs and symptoms of acute exposure to hydrocyanic acid may include hypertension (high blood pressure) and tachycardia (rapid heart rate), followed by hypotension (low blood pressure) and bradycardia (slow heart rate). Cherry red mucous membranes and blood may be noted. Cardiac arrhythmias and other cardiac abnormalities are common. Cyanosis (blue tint to the skin and mucous membranes) may be observed. Weakness, headache, vertigo (dizziness), agitation, giddiness, salivation, nausea, and vomiting, may be followed by combative behavior, convulsions, paralysis, protruding eyeballs, dilated and unreactive pupils, and coma. Tachypnea (rapid, shallow respirations) or hyperpnea (rapid, deep respirations) may be followed by respiratory depression. Lung hemorrhage and pulmonary edema may also occur. Hydrocyanic acid is may be irritating to the skin, eyes, and mucous membranes. Lacrimation (tearing) and a burning sensation of the mouth and throat are common.

Emergency Life-Support Procedures: Acute exposure to hydrocyanic acid may require decontamination and life support for the victims. All exposed persons should be transported to a health care facility as quickly as possible. Emergency personnel should wear protective clothing appropriate to the type and degree of contamination. Air-purifying or supplied-air respiratory equipment should also be worn, as necessary. Rescue vehicles should carry supplies such as plastic sheeting and disposable plastic bags to assist in preventing spread of contamination.

Inhalation Exposure:

1. Move victims to fresh air. Emergency personnel should avoid self-exposure to hydrocyanic acid.

2. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is detected, provide CPR. If not breathing, provide artificial respiration. IMMEDIATELY begin administering 100% oxygen to all victims. Monitor victims for respiratory distress.Warning: To prevent self-poisoning, avoid mouth-to-mouth breathing; use a forced-oxygen mask. Direct oral contact with hydrocyanic acid- contaminated persons or their gastric contents can result in self- poisoning.

3. RUSH to a health care facility!

4. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

Dermal/Eye Exposure:

1. Remove victims from exposure. Emergency personnel should avoid self- exposure to hydrocyanic acid.

4. Remove contaminated clothing as soon as possible.

5. If eye exposure has occurred, eyes must be flushed with lukewarm water for at least 15 minutes.

6. Wash exposed skin areas twice with soap and water.

7. Obtain authorization and/or further instructions from the local hospital for administration of an antidote or performance of other invasive procedures.

Ingestion Exposure:

1. Evaluate vital signs including pulse and respiratory rate, and note any trauma. If no pulse is detected, provide CPR. If not breathing, provide artificial respiration. IMMEDIATELY begin administering 100% oxygen to all victims. Monitor victims for respiratory distress.Warning: To prevent self-poisoning, avoid mouth-to-mouth breathing; use a forced-oxygen mask. Direct oral contact with hydrocyanic acid- contaminated persons or their gastric contents can result in self- poisoning.

2. RUSH to a health care facility!

3. DO NOT induce vomiting or attempt to neutralize!

5. Activated charcoal may be administered if victims are conscious and alert. Use 15 to 30 g (1/2 to 1 oz) for children, 50 to 100 g (1-3/4 to 3-1/2 oz) for adults, with 125 to 250 mL (1/2 to 1 cup) of water.

6. Promote excretion by administering a saline cathartic or sorbitol to conscious and alert victims. Children require 15 to 30 g (1/2 to 1 oz) of cathartic; 50 to 100 g (1-3/4 to 3-1/2 oz) is recommended for adults. (EPA, 1998)

Excerpt from NIOSH Pocket Guide for Hydrogen cyanide:

Eye: IRRIGATE IMMEDIATELY - If this chemical contacts the eyes, immediately wash (irrigate) the eyes with large amounts of water, occasionally lifting the lower and upper lids. Get medical attention immediately.

Skin: WATER FLUSH IMMEDIATELY - If this chemical contacts the skin, immediately flush the contaminated skin with water. If this chemical penetrates the clothing, immediately remove the clothing and flush the skin with water. Get medical attention promptly.

Breathing: RESPIRATORY SUPPORT - If a person breathes large amounts of this chemical, move the exposed person to fresh air at once. If breathing has stopped, perform artificial respiration. Keep the affected person warm and at rest. Get medical attention as soon as possible.

Swallow: MEDICAL ATTENTION IMMEDIATELY - If this chemical has been swallowed, get medical attention immediately. (NIOSH, 2024)

General First Aid:

· Call 911 or emergency medical service.

· Ensure that medical personnel are aware of the material(s) involved, take precautions to protect themselves and avoid contamination.

· Move victim to fresh air if it can be done safely.

· Administer oxygen if breathing is difficult.

· If victim is not breathing:

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

SMALL FIRE: Dry chemical, CO2 or water spray.

LARGE FIRE: Dry chemical, CO2, alcohol-resistant foam or water spray. If it can be done safely, move undamaged containers away from the area around the fire. Dike runoff from fire control for later disposal.

FIRE INVOLVING TANKS, RAIL TANK CARS OR HIGHWAY TANKS: Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles. Do not get water inside containers. Cool containers with flooding quantities of water until well after fire is out. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks in direct contact with flames. (ERG, 2024)

Excerpt from ERG Guide 117 [Gases - Toxic - Flammable (Extreme Hazard); polymerization hazard]:

DO NOT EXTINGUISH A LEAKING GAS FIRE UNLESS LEAK CAN BE STOPPED.

SMALL FIRE: Dry chemical, CO2, water spray or regular foam.

LARGE FIRE: Water spray, fog or regular foam. If it can be done safely, move undamaged containers away from the area around the fire. Damaged cylinders should be handled only by specialists.

FIRE INVOLVING TANKS: Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles. Cool containers with flooding quantities of water until well after fire is out. Do not direct water at source of leak or safety devices; icing may occur. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks in direct contact with flames. (ERG, 2024)

For information on chemical warfare blood agents see the ERG Criminal or Terrorist Use of CBR Agents. (ERG, 2024)

Firefighting should be done from a safe distance. A few whiffs of gas, or liquid penetrating firefighter's protective clothing, could be fatal. Only special protective clothing should be worn. Water spray should be used to keep containers cool. Keep unnecessary people away; isolate hazard area and deny entry. Stay upwind; keep out of low areas. Ventilate closed spaces before entering them. Wear positive pressure breathing apparatus and special protective clothing. Evacuate area endangered by gas. Isolate for 1/2 mile in all directions if tank car or truck is involved in fire.

Use dry chemicals, alcohol foam, or carbon dioxide. Small fires: let burn unless leak can be stopped immediately. Large fires: water spray, fog or foam. Move container from fire area if you can do it without risk. Stay away from ends of tanks. Withdraw immediately in case of rising sound from venting safety device or any discoloration of tank due to fire. Cool container with water using unmanned device until well after fire is out. Isolate area until gas has dispersed. (EPA, 1998)

Excerpt from ERG Guide 152 [Substances - Toxic (Combustible)]:

LARGE FIRE: Water spray, fog or regular foam. If it can be done safely, move undamaged containers away from the area around the fire. Dike runoff from fire control for later disposal. Avoid aiming straight or solid streams directly onto the product.

FIRE INVOLVING TANKS, RAIL TANK CARS OR HIGHWAY TANKS: Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles. Do not get water inside containers. Cool containers with flooding quantities of water until well after fire is out. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank. ALWAYS stay away from tanks in direct contact with flames. For massive fire, use unmanned master stream devices or monitor nozzles; if this is impossible, withdraw from area and let fire burn. (ERG, 2024)

Shut off supply; if not possible and no risk to surroundings, let the fire burn itself out. In other cases extinguish with powder, water spray, alcohol-resistant foam, carbon dioxide. In case of fire: keep cylinder cool by spraying with water. Combat fire from a sheltered position.

- Fire will produce irritating, corrosive, and/or toxic gases.

- UN 1051, hydrogen cyanide (AC), >20% solution or anhydrous, is extremely flammable.

- UN 1051 may be ignited by heat, sparks, or flames.

- UN 1614, hydrogen cyanide (AC), stabilized and UN 3294, hydrogen cyanide (AC) solution in alcohol, are highly flammable.

- UN 1614 and UN 3294 will be easily ignited by heat, sparks, or flames.

- Caution: UN 1614 and UN 3294 have very low flash points. Use of water spray when fighting fires may be inefficient.

- UN 1613, hydrogen cyanide (AC), not more than 20% solution, is non-combustible.

- UN 1613 itself does not burn, but it may decompose upon heating to produce corrosive and/or toxic fumes.

- UN 1613 may be an oxidant, and it may ignite combustibles (wood, paper, oil, clothing, etc.).

- Vapors of UN 1051, UN 1614, or UN 3294 may travel to the source of ignition and flash back.

- Run-off of UN 1051, UN 1614, or UN 3294 may create a fire hazard.

- Do not extinguish a leaking gas fire of UN 1051 unless the leak can be stopped.

- For small fires, use dry chemical, carbon dioxide, or water spray. Regular foam may also be used on small fires involving UN 1051. Alcohol-resistant foam may also be used on small fires involving UN 1614 or UN 3294.

- For large fires involving UN 1051, use water spray, fog, or regular foam. For UN 1614 or UN 3294, use water spray, fog, or alcohol-resistant foam. For UN 1613, use dry chemical, carbon dioxide, alcohol-resistant foam, or water spray. Move containers from the fire area if it is possible to do so without risk to personnel. Dike fire control water for later disposal; do not scatter the agent. Use water spray or fog; do not use straight streams. Damaged cylinders of UN 1051 should be handled only by specialists.

- For fire involving tanks or car/trailer loads, fight the fire from maximum distance or use unmanned hose holders or monitor nozzles. Do not get water inside containers of UN 1613. Cool containers with flooding quantities of water until well after the fire is out. Do not direct water at the source of the leak of UN 1051 or at safety devices; icing may occur. Withdraw immediately in case of rising sound from venting safety devices or discoloration of tanks. Always stay away from tanks engulfed in fire.

- For massive fire involving UN 1614 or UN 3294, use unmanned hose holders or monitor nozzles; if this is impossible, withdraw from the area and let the fire burn.

- Run-off from fire control or dilution water may be corrosive and/or toxic, and it may cause pollution.

- If the situation allows, control and properly dispose of run-off (effluent).

Fire situation may require evacuation. Allow burning of material until flow of gas can be stopped. Use water spray, dry chemical, "alcohol resistant" foam, or carbon dioxide. Water may be ineffective. Approach fire from upwind. Fight fire from protected location or maximum possible distance.

Shut off supply; if not possible and no risk to surroundings, let the fire burn itself out; in other cases extinguish with powder, water spray, foam, carbon dioxide.

Cyanide salts must be protected from large concn of carbon dioxide to avoid hydrogen cyanide liberation. Carbon dioxide fire extinguishers should not be used. /Cyanide salts/

If material on fire or involved in fire: Do not extinguish fire unless flow can be stopped. Use water in flooding quantities as fog. Cool all affected containers with flooding quantities of water. Apply water from as far a distance as possible. Solid streams of water may be ineffective. Use "alcohol" foam, dry chemical or carbon dioxide. /Hydrogen cyanide, aqueous solution; Hydrogen cyanide, solution in alcohol; Hydrogen cyanide, stabilized (with less than 3% water); Hydrogen cyanide, stabilized (with less than 3% water absorbed in a porous material)/

If fire becomes uncontrollable or container is exposed to direct flame - consider evacuation of one-half (1/2) mile radius. /Hydrogen cyanide, aqueous solution; Hydrogen cyanide, solution in alcohol; Hydrogen cyanide, stabilized (with less than 3% water); Hydrogen cyanide, stabilized (with less than 3% water absorbed in a porous material)/

Flashback along vapor trail may occur.

· CALL 911. Then call emergency response telephone number on shipping paper. If shipping paper not available or no answer, refer to appropriate telephone number listed on the inside back cover.

· Keep unauthorized personnel away.

· Stay upwind, uphill and/or upstream.

· Ventilate closed spaces before entering, but only if properly trained and equipped.

· ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area.

· Do not touch damaged containers or spilled material unless wearing appropriate protective clothing.

· Stop leak if you can do it without risk.

· Prevent entry into waterways, sewers, basements or confined areas.

· Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers.

· DO NOT GET WATER INSIDE CONTAINERS.

· Many gases are heavier than air and will spread along the ground and collect in low or confined areas (sewers, basements, tanks, etc.).

· All equipment used when handling the product must be grounded.

· Do not touch or walk through spilled material.

· Use water spray to reduce vapors or divert vapor cloud drift. Avoid allowing water runoff to contact spilled material.

· Do not direct water at spill or source of leak.

· If possible, turn leaking containers so that gas escapes rather than liquid.

· Isolate area until gas has dispersed.

· Consider igniting spill or leak to eliminate toxic gas concerns.

· Cover with plastic sheet to prevent spreading.

· A vapor-suppressing foam may be used to reduce vapors.

Small Spill

· Absorb with earth, sand or other non-combustible material and transfer to containers for later disposal.

· Use clean, non-sparking tools to collect absorbed material.

Large Spill

· Dike far ahead of liquid spill for later disposal.

· Water spray may reduce vapor, but may not prevent ignition in closed spaces.

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids.

SPILL: See ERG Table 1 - Initial Isolation and Protective Action Distances on the UN/NA 1613 datasheet.

FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 800 meters (1/2 mile) in all directions; also, consider initial evacuation for 800 meters (1/2 mile) in all directions. (ERG, 2024)

Excerpt from ERG Guide 117 [Gases - Toxic - Flammable (Extreme Hazard); polymerization hazard]:

IMMEDIATE PRECAUTIONARY MEASURE: Isolate spill or leak area for at least 100 meters (330 feet) in all directions.

SPILL: See ERG Table 1 - Initial Isolation and Protective Action Distances on the UN/NA 1051 datasheet.

FIRE: If tank, rail tank car or highway tank is involved in a fire, ISOLATE for 1600 meters (1 mile) in all directions; also, consider initial evacuation for 1600 meters (1 mile) in all directions. (ERG, 2024)

For initial isolation and protective action distances for chemical warfare blood agents see the Chemical Warfare Agents table in the ERG Criminal or Terrorist Use of CBR Agents. (ERG, 2024)

Excerpt from ERG Guide 152 [Substances - Toxic (Combustible)]:

SPILL: See ERG Table 1 - Initial Isolation and Protective Action Distances on the UN/NA 1614 datasheet.

Immediate precautionary measure

· Isolate spill or leak area in all directions for at least 50 meters (150 feet) for liquids and at least 25 meters (75 feet) for solids.

· For highlighted materials: see Table 1 - Initial Isolation and Protective Action Distances.

Excerpt from ERG Guide 154 [Substances - Toxic and/or Corrosive (Non-Combustible)]:

ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area. Do not touch damaged containers or spilled material unless wearing appropriate protective clothing. Stop leak if you can do it without risk. Prevent entry into waterways, sewers, basements or confined areas. Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. DO NOT GET WATER INSIDE CONTAINERS. (ERG, 2024)

Excerpt from ERG Guide 117 [Gases - Toxic - Flammable (Extreme Hazard); polymerization hazard]:

ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area. All equipment used when handling the product must be grounded. Do not touch or walk through spilled material. Stop leak if you can do it without risk. Use water spray to reduce vapors or divert vapor cloud drift. Avoid allowing water runoff to contact spilled material. Do not direct water at spill or source of leak. If possible, turn leaking containers so that gas escapes rather than liquid. Prevent entry into waterways, sewers, basements or confined areas. Isolate area until gas has dispersed. Consider igniting spill or leak to eliminate toxic gas concerns. (ERG, 2024)

For information on chemical warfare blood agents see the ERG Criminal or Terrorist Use of CBR Agents. (ERG, 2024)

Excerpt from ERG Guide 152 [Substances - Toxic (Combustible)]:

ELIMINATE all ignition sources (no smoking, flares, sparks or flames) from immediate area. Do not touch damaged containers or spilled material unless wearing appropriate protective clothing. Stop leak if you can do it without risk. Prevent entry into waterways, sewers, basements or confined areas. Cover with plastic sheet to prevent spreading. Absorb or cover with dry earth, sand or other non-combustible material and transfer to containers. DO NOT GET WATER INSIDE CONTAINERS. (ERG, 2024)

Store only if stabilized. Fireproof. Cool. Separated from food and feedstuffs and incompatible materials. See Chemical Dangers. Store in an area without drain or sewer access.

Keep cylinders of hydrogen cyanide (HCN) cool and away from open flames. Make certain that HCN cylinders are adequately supported and grounded during storage and emptying. Store cylinders in a vertical position. Do not drop cylinders or damage them by impact. Cylinders must be returned to the supplier within 90 days of the filling date marked on the cylinders, regardless of whether or not the contents have been used. This is due to the possibility of HCN becoming unstable over time. If there is any indication that the HCN is becoming unstable, such as a darkening of the product or an increase in cylinder pressure, contact the supplier immediately for instructions.

Fireproof. Separated from food and feedstuffs. Cool. Store only if stabilized.

Store in a cool, dry, well-ventilated location. Shelf life should not exceed 90 days or as otherwise specified by manufacturer.

Handling, storage, and transportation of hydrogen cyanide are determined by its low boiling point, high toxicity, and instability in the presence of moisture, bases, or other impurities. The liquid acid is relatively uncorrosive. Materials compatible with HCN at normal temperatures are stainless steel, Hastelloy, and Monel. To prevent polymerization, stabilizing agents, such as sulfuric acid, phosphoric acid, oxalic or acetic acid, and sulfur dioxide are used. The type and quantity of stabilizer (usually <0.5%) depend on storage capacity, temperature, and residence time in a container. A combination of H2SO4 and SO2 prevents the decomposition of HCN in the liquid and vapor phases. Larger quantities of hydrogen cyanide are stored at a maximum temperature of 5 °C and must be permanently recirculated. Additionally, the color of the liquid is monitored and should not exceed APHA 20. To keep the concentration of gas below the danger level, good ventilation of buildings in which HCN is stored and handled is of primary importance.

· Wear positive pressure self-contained breathing apparatus (SCBA).

· Wear chemical protective clothing that is specifically recommended by the manufacturer when there is NO RISK OF FIRE.

· Structural firefighters' protective clothing provides thermal protection but only limited chemical protection.

TIH (Toxic Inhalation Hazard) - Term used to describe gases and volatile liquids that are toxic when inhaled. Some are TIH materials themselves, e.g., chlorine, and some release TIH gases when spilled in water, e.g., chlorosilanes. [ERG 2016].

1.9 [ppm]

AEGL 1: Notable discomfort, irritation, or certain asymptomatic non-sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure (Unit: ppm)

AEGL 2: Irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape (Unit: ppm)

AEGL 3: Life-threatening health effects or death (Unit: ppm)

AEGLs Status: Final

2.0 [ppm]

7.1 [ppm]

15 [ppm]

4.7 ppm (5 mg/m³)

ST 4.7 ppm (5 mg/m3) [skin]

10.0 [ppm]

10 ppm (11 mg/m³)

TWA 10 ppm (11 mg/m3) [skin] See Appendix G

50 ppm [From NPG: Hydrogen cyanide] (NIOSH, 2024)

50 ppm (NIOSH, 2024)

50.0 [ppm]

Excerpts from Documentation for IDLHs: It has been reported that 45 to 54 ppm can be tolerated for 0.5 to 1 hour without immediate or delayed effects while 110 to 135 ppm may be fatal after 0.5 to 1 hour or later, or dangerous to life [Flury and Zernik 1931].

See: 74908

4.7 [ppm], as CN

Ceiling Limit: 4.7 ppm, skin.

(ceiling value): 4.7 ppm as STEL; (skin).

4.7 ppm [1991]

Small Fire

· Dry chemical, CO2 or water spray.

Large Fire

· Dry chemical, CO2, alcohol-resistant foam or water spray.

· If it can be done safely, move undamaged containers away from the area around the fire.

· Dike runoff from fire control for later disposal.

Fire Involving Tanks, Rail Tank Cars or Highway Tanks

· Fight fire from maximum distance or use unmanned master stream devices or monitor nozzles.

· Do not get water inside containers.

· Cool containers with flooding quantities of water until well after fire is out.

· Withdraw immediately in case of rising sound from venting safety devices or discoloration of tank.

· ALWAYS stay away from tanks in direct contact with flames.

· DO NOT EXTINGUISH A LEAKING GAS FIRE UNLESS LEAK CAN BE STOPPED.

· Dry chemical, CO2, water spray or regular foam.

Hydrocyanic acid, aqueous solution, with not more than 20% hydrogen cyanide is a clear colorless aqueous solution of a gas. Has a faint odor of almonds. Can evolve hydrogen cyanide gas, which is (barely) lighter than air. Flame can flash back to the source of a gas leak very easily. Lethal doses of gas may be inhaled. Lethal doses of cyanide can be absorbed from the solution through the skin.

Hydrocyanic acid, aqueous solutions, with more than 20% hydrogen cyanide is a clear colorless aqueous solution of a gas. Has an odor of almonds. Can evolve hydrogen cyanide gas, which is (barely) lighter than air. Flame can flash back to the source of a gas leak very easily. Lethal doses of gas may be inhaled. Lethal doses of cyanide can be absorbed from the solution through the skin.

Hydrogen cyanide, anhydrous, stabilized appears as a chemical warfare blood agent. A deadly human poison by all routes. Very volatile. Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor. Often used as a 96% solution in water. (NIOSH, 2024)

Hydrogen cyanide, anhydrous, stabilized (absorbed) appears as a clear colorless liquid with a faint odor of bitter almonds that is absorbed in a porous inert material. Absorption slows evolution of vapors. Vapors slightly lighter than air. Deadly poison by all routes (absorption through skin of liquid, inhalation of vapors, etc). Prolonged exposure of closed containers to heat may cause violent rupture and rocketing. Rate of onset: Immediate Persistence: Minutes Odor threshold: 1-5 ppm Source/use/other hazard: War gas, pesticide, Herbicide; other industries; Weak acid except in water or mucous membranes - then corrosive/training.

Liquid; Gas Vapor; Liquid; Gas Vapor

Colorless or pale-blue liquid or gas (above 78 degrees F) with a bitter, almond-like odor. [Note: Often used as a 96% solution in water.] [NIOSH]

COLOURLESS GAS OR LIQUID WITH CHARACTERISTIC ODOUR.

Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor.

Colorless or pale-blue liquid or gas (above 78 °F) with a bitter, almond-like odor. [Note: Often used as a 96% solution in water.]

Colorless or pale blue liquid below 78°F (25.6°C), colorless gas above 78°F (25.6°C).

Colorless gas or liquid

Water-white liquid below 26.5 °C

Colorless or pale-blue liquid or gas (above 78 °F) ... [Note: Often used as a 96% solution in water]

Bitter almond odor

... Bitter, almond-like odor.

Bitter, burning taste

78 °F at 760 mmHg (96%) (NIOSH, 2024)

25.63 °C

79.00 °C. @ 0.00 mm Hg

78 °F (96%)

26 °C @760 [mm Hg]

7 °F (96%) (NIOSH, 2024)

-13.28 °C

5.00 °C. @ 0.00 mm Hg

7 °F (96%)

-13.29 °C

0 °F (96%) (NIOSH, 2024)

0 °F (-18 °C) (Closed cup)

-18 °C c.c.

0 °F (96%)

Miscible (NIOSH, 2024)

Miscible with water

Miscible with ethanol, ethyl ether

Miscible with alcohol; slightly soluble in ether

1.00E+06 mg/L @ 25 °C (exp)

Solubility in water: miscible

Miscible

0.69 (NIOSH, 2024) - Less dense than water; will float

0.6875 g/cu cm at 20 °C

Density: (gas) 0.941 (Air = 1); (liq) 0.687

No rapid reaction with air. No rapid reaction with water.

Highly flammable. Flame may easily travel back to source of leak. Vapors forms explosive mixtures with air. Soluble in water.

Highly flammable but absorption can prevent evolution of enough vapors to ignite. Flame may easily travel back to source of leak. Vapors forms explosive mixtures with air. Soluble in water (exception of absorbing material).

Cyanides, Inorganic

Acids, Weak

Polymerizable Compounds

Water and Aqueous Solutions

Polymerizable

Highly Flammable

HYDROCYANIC ACID, AQUEOUS SOLUTION, WITH NOT MORE THAN 20% HYDROGEN CYANIDE reacts with acid to evolve hydrogen cyanide, a very poisonous colorless gas smelling of bitter almonds which is a deadly human poison by all routes. Carbon dioxide from the air is sufficiently acidic to liberate HCN from aqueous solutions of hydrocyanic acid [Lewis]. The solution also can evolve gaseous hydrogen cyanide when heated. Inhalation of gaseous HCN is quickly fatal by respiratory arrest. The gas forms flammable or explosive mixtures with air (may be difficult to ignite at lower concentrations). It presents an explosion hazard when heated with or exposed to other oxidizing agents and may polymerize explosively at elevated temperature (50-60 °C) or in the presence of traces of alkali [Wohler, L. et al., Chem. Ztg., 1926, 50, p. 761, 781]. It reacts violently with acetaldehyde. During the preparation of imidoester hydrochlorides, hydrogen chloride was rapidly passed over an alcoholic solution of hydrogen cyanide. An explosion ensued, despite cooling of the process [J. Org. Chem., 1955, 20, 1573]. In the absence of a stabilizer (e.g. phosphoric acid) it may undergo explosively rapid spontaneous (autocatalytic) polymerization leading to a fire. The reaction is autocatalytic because of ammonia formation [Bond, J., Loss Prev. Bull., 1991, 101, p.3].

HYDROCYANIC ACID, AQUEOUS SOLUTIONS, WITH MORE THAN 20% HYDROGEN CYANIDE react with acid to evolve hydrogen cyanide, a very poisonous colorless gas smelling of bitter almonds. Carbon dioxide from the air is sufficiently acidic to liberate HCN from aqueous solutions of hydrocyanic acid [Lewis]. The solution also can evolve gaseous hydrogen cyanide when heated. Inhalation of gaseous HCN is quickly fatal by respiratory arrest. The gas forms flammable or explosive mixtures with air (may be difficult to ignite at lower concentrations). It presents an explosion hazard when heated with or exposed to other oxidizing agents and may polymerize explosively at elevated temperature (50-60 °C) or in the presence of traces of alkali [Wohler, L. et al., Chem. Ztg., 1926, 50, p. 761, 781]. Reacts violently with acetaldehyde. During the preparation of imidoester hydrochlorides, hydrogen chloride was rapidly passed over an alcoholic solution of hydrogen cyanide. An explosion ensued, despite cooling of the process [J. Org. Chem., 1955, 20, 1573].

HYDROGEN CYANIDE, ANHYDROUS presents a severe explosion hazard when exposed to oxidizing agents. The vapors form explosive mixtures with air. May polymerize explosively at elevated temperature (50-60 °C) or in the presence of traces of alkali [Wohler, L. et al., Chem. Ztg., 1926, 50, p. 761, 781]. In the absence of a stabilizer (such as phosphoric acid), may undergo explosively rapid spontaneous (autocatalytic) polymerization leading to a fire. The reaction is autocatalytic because of ammonia formation. [Bond, J., Loss Prev. Bull., 1991, 101, p.3]. Dissolves in water to give weakly acidic solutions. Reacts violently with acetaldehyde. During the preparation of imidoester hydrochlorides, hydrogen chloride was rapidly passed over alcoholic hydrogen cyanide. An explosion ensued, even with cooling of the process [J. Org. Chem., 1955, 20, 1573].

HYDROGEN CYANIDE, ANHYDROUS reacts as an oxidizing agent and as a weak acid. Absorption moderates its reactivity. Presents an explosion hazard when heated or exposed to oxidizing agents. Reacts violently with acetaldehyde. May polymerize explosively at elevated temperature. May polymerize in the presence of traces of alkali [Wohler, L. et al., Chem. Ztg., 1926, 50, p. 761, 781]. During the preparation of imidoester hydrochlorides, hydrogen chloride was rapidly passed over an alcoholic solution of hydrogen cyanide. An explosion ensued, even with cooling of the process [J. Org. Chem., 1955, 20, 1573].

Preparation of alkyliminoformate chlorides by passing hydrogen chloride rapidly into alcoholic hydrogen cyanide proceeds explosively (probably owing to a sudden exotherm), even with strong cooling.

Cyanogen halides may be prepared by electrolysis of hydrogen cyanide or its salts mixed with halide salts. If ammonium chloride is used as the halide salt, precautions to prevent formation of explosive nitrogen trichloride are necessary.

Avoid addition of such alkaline chemicals as sodium hydroxide, ammonia, calcium hydroxide, and sodium carbonate to hydrogen cyanide since they promote polymerization and induce decomposition, which may cause an explosion. Also, avoid addition of large quantities of acid to hydrogen cyanide, for similar reasons.

Severe explosion hazard when exposed to heat or flame or by chemical reaction with oxidizers.

For more Hazardous Reactivities and Incompatibilities (Complete) data for Hydrogen cyanide (6 total), please visit the HSDB record page.

Amines, oxidizers, acids, sodium hydroxide, calcium hydroxide, sodium carbonate, caustics, ammonia [Note: Can polymerize at 122-140 °F.]

IDENTIFICATION AND USE: Hydrogen cyanide is a colorless or pale blue liquid or gas with a faint bitter almond like odor. Hydrogen cyanide is used primarily in the production of substances such as adiponitrile, methyl methacrylate, chelating agents, cyanuric chloride, methionine and its hydroxylated analogues, and sodium and potassium cyanide. Hydrogen cyanide is also used as a fumigant in ships, railroad cars, large buildings, grain silos, and flour mills, as well as in the fumigation of peas and seeds in vacuum chambers. Hydrogen cyanide is formed during the incomplete combustion of nitrogen-containing polymers, such as certain plastics, polyurethanes, and wool. Hydrogen cyanide is also present in cigarette smoke. HUMAN STUDIES: The primary targets of cyanide toxicity in humans are the cardiovascular, respiratory, and central nervous systems. The endocrine system is also a potential target for long term toxicity, as a function of continued exposure to thiocyanate, which prevents the uptake of iodine in the thyroid and acts as a goitrogenic agent. Sequelae after severe acute intoxications may include neuropsychiatric manifestations and Parkinson type disease. Cyanide from tobacco smoke has been implicated as a contributing factor in tobacco alcohol amblyopia. Long term exposure to lower concentrations of cyanide in occupational settings can result in a variety of symptoms related to central nervous system effects. Cyanides are weakly irritating to the skin and eye. ANIMAL STUDIES: The principal features of the toxicity profile for cyanide are its high acute toxicity by all routes of administration, with a very steep and rate-dependent dose effect curve, and chronic toxicity, probably mediated through the main metabolite and detoxification product, thiocyanate. The toxic effects of cyanide ion in humans and animals are generally similar and are believed to result from inactivation of cytochrome oxidase and inhibition of cellular respiration and consequent histotoxic anoxia. The primary targets of cyanide toxicity in animals are the cardiovascular, respiratory, and central nervous systems. The endocrine system is also a potential target for long-term toxicity, as a function of continued exposure to thiocyanate, which prevents the uptake of iodine in the thyroid and acts as a goitrogenic agent. In a 13 week repeated-dose toxicity study in which cyanide was administered in drinking-water, there were no clinical signs associated with central nervous system effects or histopathological effects in the brain or thyroid of rats or mice. There were slight changes in the reproductive tract in male rats. The examination of neurotoxicity in this study was limited to clinical observation and optical microscopy in autopsy. The few available studies specifically intended to investigate neurotoxicity, while reporting adverse effects at exposure levels of 1.2 mg cyanide/kg body weight per day in rats and 0.48 mg cyanide/kg body weight per day in goats, suffer from weaknesses that preclude their quantitative assessment. In relation to characterization of concentration-response for repeated-dose toxicity for inhalation (relevant principally to the occupational environment), in three separate studies in rats, there were no adverse systemic effects in rats exposed to acetone cyanohydrin, which is rapidly hydrolyzed to hydrogen cyanide at physiological pH, at concentrations up to 211 mg/cu m (corresponding to a concentration of 67 mg hydrogen cyanide/cu m). The steepness of the dose effect curve is illustrated by the observation of 30% mortality among rats exposed part of the day to 225 mg acetone cyanohydrin/cu m (71 mg hydrogen cyanide/cu m). ECOTOXICITY STUDIES: Adverse effects of exposure to the low concentrations of cyanide that are generally present in the general environment (<1 ug/cu m in ambient air; <10 ug/L in water) are unlikely.

Organic nitriles decompose into cyanide ions both in vivo and in vitro. Consequently the primary mechanism of toxicity for organic nitriles is their production of toxic cyanide ions or hydrogen cyanide. Cyanide is an inhibitor of cytochrome c oxidase in the fourth complex of the electron transport chain (found in the membrane of the mitochondria of eukaryotic cells). It complexes with the ferric iron atom in this enzyme. The binding of cyanide to this cytochrome prevents transport of electrons from cytochrome c oxidase to oxygen. As a result, the electron transport chain is disrupted and the cell can no longer aerobically produce ATP for energy. Tissues that mainly depend on aerobic respiration, such as the central nervous system and the heart, are particularly affected. Cyanide is also known produce some of its toxic effects by binding to catalase, glutathione peroxidase, methemoglobin, hydroxocobalamin, phosphatase, tyrosinase, ascorbic acid oxidase, xanthine oxidase, succinic dehydrogenase, and Cu/Zn superoxide dismutase. Cyanide binds to the ferric ion of methemoglobin to form inactive cyanmethemoglobin. (L97)

No indication of carcinogenicity to humans (not listed by IARC).

Exposure to high levels of cyanide for a short time harms the brain and heart and can even cause coma, seizures, apnea, cardiac arrest and death. Chronic inhalation of cyanide causes breathing difficulties, chest pain, vomiting, blood changes, headaches, and enlargement of the thyroid gland. Skin contact with cyanide salts can irritate and produce sores. (L96, L97)

The substance can be absorbed into the body by inhalation, through the skin and by ingestion.

inhalation, skin absorption, ingestion, skin and/or eye contact

Hydrogen cyanide (AC) can affect the body by ingestion, inhalation, skin contact, or eye contact.

Oral (L96) ; inhalation (L96) ; dermal (L96)

Confusion. Drowsiness. Headache. Nausea. Shortness of breath. Convulsions. Unconsciousness. Respiratory and cardiac arrest.

MAY BE ABSORBED! Further see Inhalation.

MAY BE ABSORBED! Redness. Pain. See Inhalation.

Burning sensation. Further see Inhalation.

asphyxia; lassitude (weakness, exhaustion), headache, confusion; nausea, vomiting; increased rate and depth of respiration or respiration slow and gasping; thyroid, blood changes

- Irritation.

- Contact with only the eyes does not normally result in whole-body (systemic) toxicity.

- Contact with the eyes can contribute to whole-body (systemic) toxicity. See Inhalation Exposure.

- Burning sensation in mouth and throat, nausea, vomiting (emesis), and abdominal pain.

- Whole-body (systemic) toxicity can occur. See Inhalation Exposure.

- Mild to moderate: CNS effects: headache, confusion, anxiety, dizziness, weakness (malaise), and loss of consciousness. Cardiovascular effects: palpitations. Respiratory effects: respiratory tract irritation, difficulty breathing or shortness of breath (dyspnea), and transient increase in the rate and depth of breathing (hyperpnea). GI effects: nausea and vomiting (emesis).

- Severe: CNS effects: coma, seizures, and dilated pupils (mydriasis). Cardiovascular effects: shock, abnormal or disordered heart rhythms (dysrhythmias), critically low blood pressure, and cardiac arrest. Respiratory effects: abnormally rapid, followed by abnormally slow respirations; accumulation of fluid in the lungs (pulmonary edema); and respiratory arrest. Eye effects: dilated pupils, inflammation of the surface of the eye, and temporary blindness.

- Absorption through the skin is rapid and can contribute to whole-body (systemic) toxicity. See Inhalation Exposure.

- Absorption through the skin occurs more readily when ambient temperature and relative humidity are high.

Cyanide poisoning is identified by rapid, deep breathing and shortness of breath, general weakness, giddiness, headaches, vertigo, confusion, convulsions/seizures and eventually loss of consciousness. (L96, L97)

central nervous system, cardiovascular system, thyroid, blood

Other Poison - Chemical Asphyxiant

8.4 mg/day

IRIS Current

Hydrogen cyanide

Children

Human Health Benchmarks for Pesticides - 2021 Update

LC50 (rat) = 160 ppm/30 min

LD50: 3700 ug/kg (Subcutaneous, Rat) (N010)

LD50: 810 ug/kg (Intravenous, Rat)

LD50: 3700 ug/kg (Oral, Mouse)

LD50: 2990 ug/kg (Intraperitoneal, Mouse)

LC50: 142 ppm over 30 minutes (Inhalation, Rat) (T32)

Lethal adult dose of hydrogen cyanide is 50 mg.

An average LD50 value for dermal exposure of 100 mg CN per kg as hydrogen cyanide was estimated for humans.

An average fatal concentration for humans was estimated as 546 ppm hydrogen cyanide after a 10-minute exposure.

An average LD50 value for dermal exposure of 100 mg/kg body weight was estimated for humans. Concentrations of 7000 to 12,000 mg/cu m were estimated to be fatal after a 5-min exposure of workers with self-contained respirators without effective skin protection.

LC50 Rat inhalation 3778 mg/cu m (10 sec)

LC50 Rat inhalation 1471 mg/cu m (1 min)

LC50 Rat inhalation 493 mg/cu m (5 min)

LC50 Rat inhalation 142 ppm/30 min

LC50; Species: Asellus communis; Concentration: 2295 ug/L for 96 hr /Conditions of bioassay not specified/

LC50; Species: Gammarus pseudolimnaeous; Concentration: 169 ug/L for 96 hr /Conditions of bioassay not specified/

LC50; Species: Lagodon rhomboides (Pinfish) length 57-113 mm; Conditions: saltwater, static, 13.7-20.4 °C; Concentration: 69 ug/L for 24 hr

LC50; Species: Lepomis humilis (sunfish); Concentration: 0.18 mg/L for 24 hr /Conditions of bioassay not specified/

For more Ecotoxicity Values (Complete) data for Hydrogen cyanide (39 total), please visit the HSDB record page.

/BIRDS and MAMMALS/ First signs of cyanide toxicosis in sensitive birds appeared between 0.5 and 5 min after exposure, and included panting, eye blinking, salivation, and lethargy. In more-resistant species, such as domestic chickens, signs of toxicosis began 10 min after exposure. At higher doses, breathing in all species tested became increasingly deep and labored, followed by gasping and shallow intermittent breathing. Death usually followed in 15-30 min, although birds alive at 60 min frequently recovered. The rapid recovery of some birds exposed to cyanide may be due to the rapid metabolism of cyanide to thiocyanate and its subsequent excretion. Species sensitivity to cyanide was not related to body size but seemed to be associated with diet. Birds that feed predominantly on flesh, such as vultures, kestrels, and owls, were more sensitive to cyanide than were species that feed mainly on plant material--with the possible exception of mallard (Anas platyrhynchos)--as judged by acute oral LD50 values. /Cyanide/

/AQUATIC SPECIES/ Acute toxicity of hydrogen cyanide was determined at various temperatures from 4 degrees to 30 degrees C and oxygen concentrations of 3.36 to 9.26 mg/L on different life history stages of five species of fish: fathead minnow, Pimephales promelas Rafinesque; bluegill, Lepomis macrochirus Rafinesque; yellow perch, Perca flavescens (Mitchill); brook trout, Salvelinus fontinalis (Mitchill); and rainbow trout, Salmo gairdneri Richardson. Median lethal threshold concentrations and 96-hr LC50's were established by flow-through type biassays. Acute toxicity varied from 57 ug/L for juvenile rainbow trout to 191 ug/L for field stocks of juvenile fathead minnows. Juvenile fish were more sensitive at lower temperatures and at oxygen levels below 5 mg/L. For most species juveniles were most sensitive and eggs more resistant. /Acid/

/AQUATIC SPECIES/ Brook trout, Salvelinus fontinalis (Mitchell), were exposed to various concentrations of hydrogen cyanide to determine the effects of continuous exposure on survival, growth, and reproduction. Continuous flow experiments were begun with adults 144 days prior to spawning and were continued through a 90-day growth period of the second generation. The maximum acceptable toxicant concentration (MATC) of hydrogen cyanide was between 5.7 and 11.2 ug/L based on the spawning data.

/AQUATIC SPECIES/ The bluegill, Lepomis macrochirus Rafinesque, was subjected to various concentrations of hydrogen cyanide to determine the effects on long-term survival, growth, egg production, and egg hatchability. Intermittent-flow experiments were conducted using adults, juveniles, and newly hatched eggs in separate tests. Egg production was most sensitive to hydrogen cyanide, and the highest concentration with no adverse effect was below 5.2 ug/L HCN. Fry survival through the first 6 weeks followed in sensitivity with the no-adverse-effect level occurring between 15.6 and 19.4 ug/L HCN.

For more Ecotoxicity Excerpts (Complete) data for Hydrogen cyanide (20 total), please visit the HSDB record page.

2.30e+01

1.50e+02

8.30e-01

3.50e+00

1.50e+00

2.00e+02

1.50e-02

6.00e-04

8.00e-04

Volatile

1.00e+07

6.80e+01

4.40e+02

2.50e+00

1.10e+01

4.40e+00

The substance is very toxic to aquatic organisms.

Hydrogen cyanide's production and use as a chemical intermediate and for manufacturing nylon and specialty chemicals may result in its release to the environment through various waste streams. Its former use as an insecticidal fumigant, rodenticide and illegal use as a chemical warfare agent resulted in its direct release to the environment. Hydrogen cyanide is present in human blood and some plants. Small concentrations are also found in the stratosphere and atmosphere. If released to air, a vapor pressure of 742 mm Hg at 25 °C indicates hydrogen cyanide will exist solely as a vapor in the atmosphere. Vapor-phase hydrogen cyanide will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 530 days. Hydrogen cyanide does not contain chromophores that absorb at wavelengths >290 nm and, therefore, is not expected to be susceptible to direct photolysis by sunlight. If released to soil, hydrogen cyanide is expected to have very high mobility based upon an estimated Koc of 15. The pKa of hydrogen cyanide is 9.2, indicating that this compound will exist partially in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts. Volatilization from moist soil surfaces is expected to be an important fate process based upon a Henry's Law constant of 1.33X10-4 atm-cu m/mole. Hydrogen cyanide may volatilize from dry soil surfaces based upon its vapor pressure. Hydrogen cyanide can be biodegraded by acclimated microbial cultures and sludges, but is usually toxic at high concentrations to unacclimated microbial systems, indicating that biodegradation may not be an important environmental fate process in soil and water. If released into water, hydrogen cyanide is not expected to adsorb to suspended solids and sediment based upon the estimated Koc. Volatilization from water surfaces is expected to be an important fate process based upon this compound's Henry's Law constant. Estimated volatilization half-lives for a model river and model lake are 5 hrs and 3 days, respectively. An estimated BCF of 3 suggests the potential for bioconcentration in aquatic organisms is low. Hydrolysis is not expected to be an important environmental fate process since this compound contains lacks functional groups that hydrolyze under environmental conditions (pH 5 to 9). Occupational exposure to hydrogen cyanide may occur through inhalation and dermal contact with this compound at workplaces where hydrogen cyanide is produced or used. Monitoring data indicate that the general population may be exposed to hydrogen cyanide via inhalation of cigarette smoke, ingestion of specific foods. (SRC)

Hydrogen cyanide is present in human blood. It is theorized that the compound played the key role in the origin of flora and fauna on earth via formation of amino acids. Small concentrations are also found in the stratosphere and atmosphere(1). Hydrogen cyanide has been reported present in some plants(2,3).

Molecular hydrogen cyanide may be produced naturally by microorganisms as well as from the cyanogenic degradation of glycosides. ... Many plants may synthesize cyanoglucosides which upon decomposition may lead to the formation of free cyanide. ... Many photosynthetic microorganisms among the blue-green algae can produce free cyanide in the process of nitrate metabolism. ... Anacystis nidulans, a microscopic blue-green algae, used histidine to release substantial amounts of hydrogen cyanide, raising its concentration in the culture medium to 0.5 mg/L in 3 hr.

Laetrile and amygdalin-containing fruit pits /cherries, peaches, apricots, apples, and pears/ have been implicated as causes of acute cyanide poisoning in humans(1). /Cyanides/

Hydrogen cyanide's production and use as a chemical intermediate and for manufacturing nylon and specialty chemicals(1,3) may result in its release to the environment through various waste streams(SRC). Its former use as an insecticidal fumigant(2), rodenticide and illegal use as a chemical warfare agent(3) resulted in its direct release to the environment(SRC).

Hydrogen cyanide may be generated in blast furnaces, gas works, and coke ovens.

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 15(SRC), determined from a log Kow of -0.25(2) and a regression-derived equation(3), indicates that hydrogen cyanide is expected to have very high mobility in soil(SRC). The pKa of hydrogen cyanide is 9.2(4), indicating that this compound will exist partially in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(5). By analogy to the fate of cyanides in water, it is predicted that the fate in soil would be pH dependent. Cyanide may occur in the form of hydrogen cyanide, alkali metal salts, or immobile metallocyanide complexes. At soil surfaces with pH <9.2, it is expected that volatilization of hydrogen cyanide would be an important loss mechanism for cyanides. In subsurface soil, cyanide present at low concentrations would probably biodegrade(6). Volatilization of hydrogen cyanide from moist soil surfaces is expected to be an important fate process(SRC) given a Henry's Law constant of 1.33X10-4 atm-cu m/mole(7). Hydrogen cyanide is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 742 mm Hg at 25 °C(8). Hydrogen cyanide can be biodegraded by acclimated microbial cultures and sludges, but is usually toxic at high concentrations to unacclimated microbial systems(9), indicating that biodegradation may not be an important environmental fate process in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 15(SRC), determined from a log Kow of -0.25(2) and a regression-derived equation(3), indicates that hydrogen cyanide is not expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(4) based upon a Henry's Law constant of 1.33X10-4 atm-cu m/mole(5). Using this Henry's Law constant and an estimation method(4), volatilization half-lives for a model river and model lake are 5 hrs and 3 days, respectively(SRC). A pKa of 9.2(6) indicates hydrogen cyanide will exist partially in the anion form at pH values of 5 to 9 and, therefore, volatilization from water surfaces is not expected to be an important fate process(SRC). According to a classification scheme(7), an estimated BCF of 3(SRC), from its log Kow(2) and a regression-derived equation(3), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Hydrogen cyanide can be biodegraded by acclimated microbial cultures and sludges, but is usually toxic at high concentrations to unacclimated microbial systems(8), indicating that biodegradation may not be an important environmental fate process in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), hydrogen cyanide, which has a vapor pressure of 742 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase hydrogen cyanide is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 530 days(SRC), calculated from its rate constant of 3.0X10-14 cu cm/molecule-sec at 25 °C(3). Hydrogen cyanide does not contain chromophores that absorb at wavelengths >290 nm(3) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC).

AEROBIC: The metabolism of cyanide (10 mg/L) was studied using acclimated heterogeneous cultures in an aerated microferometer(1). It was determined that cyanide was readily biodegradable by acclimated cultures but highly toxic to non-acclimated cultures(1). The fungus Gloeocercospora sorghi was shown to convert hydrogen cyanide to formamide in the presence of water(2).

AEROBIC: Waste water treatment; sludge digestion: at 25 mg/L: no adverse effect in 24 days; at 30 mg/L: initial retarding effect for 6 days; at 50 mg/L: 10% reduction in gas production.

PURE CULTURE: Bacteria and protozoa may degrade cyanide by converting it to carbon dioxide and ammonia(1). /Cyanide/

The rate constant for the vapor-phase reaction of hydrogen cyanide with photochemically-produced hydroxyl radicals is 3.0X10-14 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of about 530 days at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(1). Reaction products formed are carbon monoxide and nitric oxide(2). Hydrogen cyanide is not expected to undergo hydrolysis in the environment due to the lack of functional groups that hydrolyze under environmental conditions(2). Hydrogen cyanide is expected to be resistant to direct photolysis(3). Hydrogen cyanide may react with metals commonly found in soils resulting in the formation of inorganic complexes(3).

Generators of waste (equal to or greater than 100 kg/mo) containing this contaminant, EPA hazardous waste number P063 and D003, must conform with USEPA regulations in storage, transportation, treatment and disposal of waste.

SRP: Wastewater from contaminant suppression, cleaning of protective clothing/equipment, or contaminated sites should be contained and evaluated for subject chemical or decomposition product concentrations. Concentrations shall be lower than applicable environmental discharge or disposal criteria. Alternatively, pretreatment and/or discharge to a permitted wastewater treatment facility is acceptable only after review by the governing authority and assurance that "pass through" violations will not occur. Due consideration shall be given to remediation worker exposure (inhalation, dermal and ingestion) as well as fate during treatment, transfer and disposal. If it is not practicable to manage the chemical in this fashion, it must be evaluated in accordance with EPA 40 CFR Part 261, specifically Subpart B, in order to determine the appropriate local, state and federal requirements for disposal.

Principles and methods for destruction of chemical weapons: ... "Destruction of chemical weapons" means a process by which chemicals are converted in an essentially irreversible way to a form unsuitable for production of chemical weapons, and which in an irreversible manner renders munitions and other devices unusable as such. ... Each /nation/ shall determine how it shall destroy chemical weapons, except that the following processes may not be used: dumping in any body of water, land burial or open-pit burning. It shall destroy chemical weapons only at specifically designated and appropriately designed and equipped facilities. ... Each /nation/ shall ensure that its chemical weapons destruction facilities are constructed and operated in a manner to ensure the destruction of the chemical weapons; and that the destruction process can be verified under the provisions of this Convention.

Rotary kiln, heat recovery boiler, reduction furnace and quench chambers are appropriate technologies for incineration of gaseous hydrogen cyanide and hydrogen gas.

Potential candidate for rotary kiln incineration, with a temperature range of 820 to 1,600 °C and a residence time of seconds. Also, a potential candidate for fluidized bed incineration, with a temperature range of 450 to 980 °C and a residence time of seconds. Also, a potential candidate for liquid injection incineration, with a temperature range of 650 to 1,600 °C and a residence time of 0.1 to 2 seconds.

If ... THERE IS NO FIRE, go directly to the Table of Initial Isolation and Protective Action Distances /(see table below)/ ... to obtain initial isolation and protective action distances. IF THERE IS A FIRE, or IF A FIRE IS INVOLVED, go directly to the appropriate guide /(see guide(s) below)/ and use the evacuation information shown under PUBLIC SAFETY. /AC (when used as a weapon)/

Table: Table of Initial Isolation and Protective Action Distances for AC (when used as a weapon) ID: 1051 [Table#557]

If ... THERE IS NO FIRE, go directly to the Table of Initial Isolation and Protective Action Distances /(see table below)/ ... to obtain initial isolation and protective action distances. IF THERE IS A FIRE, or IF A FIRE IS INVOLVED, go directly to the appropriate guide /(see guide(s) below)/ and use the evacuation information shown under PUBLIC SAFETY. /Hydrocyanic acid, aqueous solutions, with more than 20% Hydrogen cyanide; Hydrogen cyanide, anhydrous, stabilized; Hydrogen cyanide, stabilized/

Table: Table of Initial Isolation and Protective Action Distances for Hydrocyanic acid, aqueous solutions, with more than 20% Hydrogen cyanide; Hydrogen cyanide, anhydrous, stabilized; Hydrogen cyanide, stabilized ID: 1051 [Table#558]

If ... THERE IS NO FIRE, go directly to the Table of Initial Isolation and Protective Action Distances /(see table below)/ ... to obtain initial isolation and protective action distances. IF THERE IS A FIRE, or IF A FIRE IS INVOLVED, go directly to the appropriate guide /(see guide(s) below)/ and use the evacuation information shown under PUBLIC SAFETY. /Hydrogen cyanide, solution in alcohol, with not more than 45% Hydrogen cyanide/

Table: Table of Initial Isolation and Protective Action Distances for Hydrogen cyanide, solution in alcohol, with not more than 45% Hydrogen cyanide ID: 3294 [Table#559]

If ... THERE IS NO FIRE, go directly to the Table of Initial Isolation and Protective Action Distances /(see table below)/ ... to obtain initial isolation and protective action distances. IF THERE IS A FIRE, or IF A FIRE IS INVOLVED, go directly to the appropriate guide /(see guide(s) below)/ and use the evacuation information shown under PUBLIC SAFETY. /Hydrogen cyanide, stabilized (absorbed)/

Table: Table of Initial Isolation and Protective Action Distances for Hydrogen cyanide, stabilized (absorbed) ID: 1614 [Table#560]

For more DOT Emergency Guidelines (Complete) data for Hydrogen cyanide (37 total), please visit the HSDB record page.

1051 117P

1051 117(>20% solution)

1051 117(anhydrous)

1613 154(< or =20% solution)

UN 1051; Hydrogen cyanide, stabilized with less than 3% water

UN 1613; Hydrocyanic acid, aqueous solutions or hydrogen cyanide, aqueous solutions with not more than 20% hydrogen cyanide

UN 1614; Hydrogen cyanide, stabilized, with less than 3% water and absorbed in a porous inert material

UN 3294; Hydrogen cyanide, solution in alcohol with not more than 45% hydrogen cyanide

IMO 6.1; Hydrogen cyanide, stabilized with less than 3% water; Hydrocyanic acid, aqueous solution (hydrogen cyanide, aqueous solution) with not more than 20% hydrogen cyanide; Hydrogen cyanide, stablilized containing less than 3% water and absorbed in a porous inert material; Hydrogen cyanide, solution in alcohol with not more than 45% hydrogen cyanide.

49 214 17; Hydrocyanic acid solution, less than 5% hydrocyanic acid.

49 201 25; Hydrocyanic acid, liquefied

49 201 30; Hydrocyanic acid, solution (5% or more hydrocyanic acid)

No person may /transport,/ offer or accept a hazardous material for transportation in commerce unless that person is registered in conformance ... and the hazardous material is properly classed, described, packaged, marked, labeled, and in condition for shipment as required or authorized by ... /the hazardous materials regulations (49 CFR 171-177)./

The International Maritime Dangerous Goods Code lays down basic principles for transporting hazardous chemicals. Detailed recommendations for individual substances and a number of recommendations for good practice are included in the classes dealing with such substances. A general index of technical names has also been compiled. This index should always be consulted when attempting to locate the appropriate procedures to be used when shipping any substance or article. Hydrogen cyanide, stabilized with less than 3% water; hydrocyanic acid, aqueous solution (hydrogen cyanide, aqueous solution) with not more than 20% hydrogen cyanide; hydrogen cyanide, stablilized containing less than 3% water and absorbed in a porous inert material; and hydrogen cyanide, solution in alcohol with not more than 45% hydrogen cyanide are included on the dangerous goods list. /Hydrogen cyanide, stabilized with less than 3% water; Hydrocyanic acid, aqueous solution (hydrogen cyanide, aqueous solution) with not more than 20% hydrogen cyanide; Hydrogen cyanide, stablilized containing less than 3% water and absorbed in a porous inert material; Hydrogen cyanide, solution in alcohol with not more than 45% hydrogen cyanide/

The International Air Transport Association (IATA) Dangerous Goods Regulations are published by the IATA Dangerous Goods Board pursuant to IATA Resolutions 618 and 619 and constitute a manual of industry carrier regulations to be followed by all IATA Member airlines when transporting hazardous materials. Hydrogen cyanide, stabilized with less than 3% water; hydrogen cyanide, aqueous solution with not more than 20% hydrogen cyanide; hydrogen cyanide, stabilized, containing less than 3% water and absorbed in a porous inert material; and hydrogen cyanide, solution in alcohol with not more than 45% hydrogen cyanide are included on the dangerous goods list. /Hydrogen cyanide, stabilized with less than 3% water; Hydrogen cyanide, aqueous solution with not more than 20% hydrogen cyanide; Hydrogen cyanide, stabilized, containing less than 3% water and absorbed in a porous inert material; Hydrogen cyanide, solution in alcohol with not more than 45% hydrogen cyanide/

Poison Inhalation Hazard

Poison Inhalation Hazard Flammable Liquid

Marine pollutant. Do not transport with food and feedstuffs.

UN Hazard Class: 6.1; UN Subsidiary Risks: 3; UN Pack Group: I