Hydrogen Cyanide

Overview

Exposures to hydrogen cyanide (HCN) can result in sudden collapse and death.  HCN is very unstable, and is sensitive to heat, light and moisture.  HCN will rapidly or completely vaporize, or readily disperse in air and burn.  The warning properties of HCN are very poor; 40-60% of the population is unable to smell the characteristic odor of bitter almonds and there is a wide variation in the minimum odor threshold.  Those working with HCN or reactions that could result in HCN byproducts should have amyl nitrite capsules on hand before work begins.

Emergency Procedures

For all routes of entry, early symptoms include weakness, headache, dizziness, confusion, anxiety, nausea and vomiting.  In severe cases, breathing is rapid and deep and then becomes slow and gasping.  The skin appears bright red or pink.

In case of skin contact: The liquid is not irritating but can be absorbed through unbroken skin.  Flush contaminated area with water for at least 20 minutes.  Remove and discard contaminated clothing.  If the victim is having difficulty breathing, provide antidote as described for inhalation exposure.

In case of eye contact:  Immediately flush contaminated area with  water for at least 20 minutes, separating eyelids to assure complete rinsing.  If the victim is having difficulty breathing, provide antidote as described for inhalation exposure.

In case of inhalation: Administer amyl nitrite capsules.  Crush one pearl of amyl nitrite onto a cloth and hold to the victim's nose for 15-30 seconds of each minute.  Use a new pearl every 3 to 5 minutes.  Call Public Safety at 911 and request an ambulance immediately.

In case of ingestion: Never give anything by mouth to a victim that is rapidly losing consciousness, or is unconscious or convulsing.  DO NOT INDUCE VOMITING.  Have victim drink 8 to 10 oz. of water.  If vomiting occurs naturally, rinse mouth and repeat administration of water.  If the victim is having difficulty breathing, provide antidote as described for inhalation exposure.

Handling

Never work with HCN alone.  Someone must be in view at all times and be equipped and trained to rescue.  If HCN is released, immediately leave the area until the severity of the release is determined.  Have emergency equipment readily available.  Use liquid HCN in a fume hood.  Wear chemical splash goggles and impermeable gloves, such as Teflon, Siver Shield, 4H, or butyl rubber.  Do not use PVC or polyethylene.

Liquid hydrogen cyanide is highly flammable.  Keep away from ignition sources.   Do not use near welding operations, flames or hot surfaces. It contains a stabilizer (usually phosphoric acid) that may decompose over time.  Old samples may explode if the acid stabilizer is not maintained at a sufficient concentration.  Do not attempt to open a container if the age is unknown.  

Close and check all valves before and after withdrawing HCN from the cylinder.  Never trap HCN between two valves.   Use HCN gas in a fume hood or ventilated gas cabinet.  

Storage

Empty containers may contain residues which are hazardous.  Store in a cool, dry, well-ventilated area, out of direct sunlight. Store away from heat and ignition sources; incompatible materials, or water or products containing water.  Use grounded, non-sparking ventilation systems and electrical equipment that does not provide a source of ignition.  Use suitable, approved storage cabinets, tanks, rooms and buildings.  If storing small quantities under refrigeration, use an approved, explosion-proof refrigerator.  Consider using leak detection and alarm systems.  Limit quantity of HCN in storage.  Restrict access and keep storage area separate from work areas.  Inspect containers periodically for damage or leaks.  Do not store containers more than 90 days or as recommended by supplier.  Store cylinders in a vertical position, adequately grounded and supported.  Do not drop or damage cylinders.  No part of the cylinder should be heated higher than 51 deg C. Comply with all applicable regulations for storage and handling of flammable materials.

Disposal

HCN cylinders should be returned to the compressed gas distributor when emptied or no longer used.  HCN compounds should be disposed as hazardous waste.

For More Information

See the CCInfo sheet for HCN from CCINFOweb.
 

Section 10: Chemical Specific Information