Filtering and Supplied-Air Devices

RPE divides into two families, and confusing them is dangerous.

Filtering (respirators)

Clean the surrounding air by passing it through a filter. They require the atmosphere to contain sufficient oxygen and a known contaminant within the filter's capability.

• Disposable filtering facepieces (FFP2, FFP3) — particulates only.
• Half masks with replaceable filters — particulate, gas or combined.
• Full face masks — higher protection, plus eye protection.
• Powered air purifying respirators — a blower supplies filtered air to a hood, helmet or mask, giving positive pressure and less breathing resistance.

Supplied-air (breathing apparatus)

Provide breathable air from an independent source, so they work regardless of the contaminant or the oxygen level.

• Airline systems — air from a compressor or cylinder bank via a hose, with an escape provision.
• Self-contained breathing apparatus — a worn cylinder, for entry and rescue.

The critical rule

Filtering devices must never be used in oxygen-deficient atmospheres, in confined spaces where the atmosphere is not proven and continuously monitored, for unknown contaminants, or in atmospheres immediately dangerous to life or health. Those situations require supplied air.