Hydrogen Cyanide


CAS No.74-90-8

Hydrogen cyanide (HCN) is a colorless or pale-blue liquid or gas with a bitter, almond-like odor. Hydrogen cyanide interferes with the body’s use of oxygen and may cause harm to the brain, heart, blood vessels, and lungs. Exposure can be fatal. Workers may be harmed from exposure to hydrogen cyanide. The level of exposure depends upon the dose, duration, and work being done.

Hydrogen cyanide is used in many industries. It’s used by the military as a chemical warfare agent. It is also used commercially for fumigation, electroplating, mining, chemical synthesis, and the production of synthetic fibers, plastics, dyes, and pesticides. Some examples of workers at risk of being exposed to hydrogen cyanide include the following:

  • Workers who commercially fumigate ships and buildings
  • Agricultural workers who fumigate outdoor pests in areas such as fruit orchards
  • Factory workers in industries that manufacture acrylic fibers, synthetic rubber, and plastics
  • Steel and iron workers who work in plants that harden iron and steel

NIOSH recommends that employers use Hierarchy of Controls to prevent injuries.  If you work in an industry that uses hydrogen cyanide, please read chemical labels and the accompanying Safety Data Sheets for hazard information. Visit NIOSH’s page on Managing Chemical Safety in the Workplace to learn more about controlling chemical workplace exposures.

The following resources provide information about occupational exposure to hydrogen cyanide. Useful search terms for hydrogen cyanide include “formonitrile,” “hydrocyanic acid,” and “prussic acid.”

NIOSH Chemical Resources

Logo of NIOSH Pocket Guide

The NIOSH Pocket Guide to Chemical Hazards (NPG) helps workers, employers, and occupational health professionals recognize and control workplace chemical hazards.

Logo of Manual of Analytical Methods.Cdc-pdf[PDF]

The NIOSH Manual of Analytical Methods (NMAM) is a collection of methods for sampling and analysis of contaminants in workplace air, and in the blood and urine of workers who are occupationally exposed.

Logo of Health Hazard Evaluations consisting of three letters: HHE

The Health Hazard Evaluation Program (HHE) conducts onsite investigations of possible worker exposure to chemicals. Search the HHE database for more information on hydrogen cyanide.

Related NIOSH Resources

Selected Publications

Related Resources

International Resources

Page last reviewed: November 2, 2018