What is IDLH?

IDLH means immediately dangerous to life and health.  The hazard, such as a toxic gas, poses an immediate threat to health or life, would cause irreversible adverse health affects, or would interfere with your ability to escape a confined space unaided.  Examples of gases which may pose an IDLH atmosphere include oxygen-displacing gases, such as argon, nitrogen, carbon dioxide, helium, or even steam.  The IDLH level for carbon monoxide is 1200 ppm, for example.