What type of respirator is needed when entering an IDLH (Immediately Dangerous to Life or Health) atmosphere?

When entering an IDLH (Immediately Dangerous to Life or Health) atmosphere, the requirement for a respirator is stringent due to the extreme hazards present. A supplied air respirator or self-contained breathing apparatus (SCBA) is necessary because these types of respirators provide a continuous supply of clean air independent of the surrounding environment. In an IDLH atmosphere, the conditions could result in severe respiratory distress or immediate health effects from exposure to toxic substances or oxygen-deficient air.

Supplied air respirators offer protection by delivering breathable air from a safe source, while SCBAs supply the user with compressed clean air within a tank, allowing for mobility in hazardous environments. This type of protection is crucial because filtering devices, such as NIOSH-approved filtering facepieces or full-face cartridge respirators, do not provide adequate protection against all potential contaminants found in an IDLH situation, as they can only filter out certain particles but cannot supply breathable air if the atmosphere is dangerously compromised. Therefore, using a respirator that provides a reliable source of breathable air is the only safe choice in such hazardous situations.