Respiratory Protection

Any condition described as "immediately dangerous to life or health (IDLH)" is one that poses an immediate or delayed threat to life, causes irreversible damage to an individual's health, or hinders an individual's ability to escape unaided from a dangerous atmosphere.

A hazardous atmosphere is any atmosphere that puts individuals at risk of death, incapacitation, inability to self-rescue (escape unaided from a dangerous atmosphere), injury, or severe illness from one or more of the following:

• Airborne combustible dust at a concentration that matches or exceeds its lower flammable limit (LFL)
• Flammable gas, vapor, or mist that exceeds 10% of its LFL
• Atmospheric oxygen concentration below 19.5% or above 23.5%
• Atmospheric concentration of any hazardous substance in excess of its dose or permissible exposure limit
• Any other atmospheric condition that is immediately dangerous to life or health

MSHA uses threshold limit values (TLVs) for health hazard evaluation and enforcement. Threshold limit values are time-weighted concentrations that miners may be exposed to over extended periods of time.

To learn more about MSHA Part 48 training requirements visit our MSHA Part 48 Subpart B Surface Mining Online Training web page.