Characterization of the atmosphere within vapor-resistant encapsulating personal protective equipment during...

Hazardous materials technicians may be required to wear fully encapsulated vapor-resistant (Level A) personal protective equipment (PPE) to contain and mitigate a hazardous materials emergency. It is commonly taught and practiced in hazardous material technician courses that if the wearer's self-contained breathing apparatus (SCBA) fails, the technician can remove the SCBA face piece and breathe the in-suit expired air while exiting the incident or awaiting rescue.

To determine the composition of expired air present within an encapsulating suit during exercise.

Subjects (n = 4) walked on a motor-driven treadmill (3.2 km x h(-1)) for 30 minutes while wearing encapsulating PPE and SCBA. Oxygen (O(2)) and carbon dioxide (CO(2)) levels within the PPE were monitored. Subject vital signs and end-tidal CO(2) (EtCO(2)) were continuously monitored. After treadmill exercise, rescue air from an external source was introduced into the suit.

Mean oxygen levels inside the PPE fell below the Occupational Safety and Health Administration (OSHA) definition of oxygen-deficient environment (< 19.5% O(2)) after 2 minutes of treadmill walking and were below 17% at the end of 30 minutes. Carbon dioxide levels inside the PPE exceeded 3% in all subjects by the end of the exercise protocol. Rapid return to a room-air composition of oxygen and CO(2) within the suit was accomplished with introduction of positive-pressure air from an alternate external air source.

A toxic atmosphere is rapidly created within fully encapsulating PPE during treadmill exercise of moderate intensity. Breathing the expired air within the PPE cannot be recommended during technician training. Application of an external air source to flush the suit can return the PPE atmosphere to safe limits, but requires an intentional suit breach to accomplish.