Agent Name
Hydrogen cyanide
Major Category
Toxic Gases & Vapors
Synonyms
Formonitrile; Hydrocyanic acid; Prussic acid; [NIOSH] Formic anammonide; Carbon hydride nitride (CHN); [CHEMINFO]
Category
Chemical Asphyxiants
Description
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]
Sources/Uses
Used to manufacture other chemicals and to fumigate enclosed spaces; [ATSDR ToxProfiles] Used in the following processes: electroplating, metallurgy, and photo development; HCN is a byproduct of blast furnaces, coke ovens, photoengraving, petroleum refining, and some metal mining processes. HCN is released when burning nitrogen containing compounds, e.g., wool, silk, and plastics. HCN is present in plants such as cassava roots, lima beans, and almonds. [CHEMINFO]
Comments
Virtually any substance containing both carbon and nitrogen can release cyanide when burned under certain conditions. The ability to smell cyanide is a genetically determined trait, absent in 20% to 40% of the population. Two common scenarios for generation of HCN include the accidental mixing of acid and cyanide solutions in electroplating baths and the accidental pouring of cyanide waste solutions into acid waste containers or into other waste solutions with pHs below 10.5-11. What is even less recognized by workers is the potential for generation of large quantities of HCN simply from mixing water-soluble cyanide salts with water, e.g. showering in clothes contaminated with cyanides. Short exposures of large areas of skin to solid cyanide salts or their aqueous solutions can result in dermal absorption of lethal quantities of cyanide. [Sullivan, p.705] Inhaling 600 to 700 ppm HCN for 5 min. or 200 ppm for 30 min. may be fatal. In smoke inhalation victims, hypoxia from carbon monoxide is initially indistinguishable from that due to cyanide. [ATSDR Case Studies # 15] The following chemicals can release large amounts of HCN when spilled in water: Acetone cyanohydrin, Potassium cyanide, and Sodium cyanide. [ERG 2016] See "CYANIDES."
Restricted
No longer used as a fumigant in the U.S. [EPA Pesticides]
Skin Designation (ACGIH)
Yes
Ceiling (ACGIH)
4.7 ppm, as CN
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].
Odor Threshold High
10 ppm
Lethal Concentration
LC50 (rat) = 160 ppm/30 min
Explanatory Notes
The ability to detect a bitter almond smell at 2-10 ppm is genetically deterimined: 20-40% of the population cannot. The ERG guide is for "hydrogen cyanide, stabilized" or "Hydrocyanic acid, aqueous solutions, more than 20% Hydrogen cyanide."
Other Poison
Chemical Asphyxiant
Diseases
Occupational diseases associated with exposure to this agent:
Processes
Industrial Processes with risk of exposure:
Activities
Activities with risk of exposure: