Hydrogen Cyanide (HCN): Standards & Effects

HCN Effects on Humans:

Hydrogen Cyanide can cause rapid death due to metabolic asphyxiation. Death can occur within seconds or minutes of the inhalation of high concentrations.

  • 3,404 ppm Death after 1 minute exposure

  • 270 ppm Death after 6-8 minute exposure

  • 181 ppm Death after 10-minute exposure

  • 135 ppm Death after 30-minute exposure

  • 10 ppm OSHA permissible exposure limit (PEL)

  • 4.7 ppm NIOSH recommended exposure limit (REL)

  • ppm=parts per million Recent study estimations (Hathaway et al. 1991)


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Monitors and Warns of Dangerous Levels of Hydrogen Cyanide

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5.6% HCN lower flammable limits in air (percent by volume) 40.0% upper flammable limits in air (percent by volume)