Figure 8-7. - Self-generating A-4 oxygen-breathing apparatus.

Self-Contained Demand Regulator Equipment

The demand regulator type of self-contained breathing equipment provides face and respiratory protection for the user but is limited to the amount of air or oxygen carried in the supply cylinder. This equipment consists of a full face mask, corrugated flexible breathing tube, demand regulator, air or oxygen supply cylinder, and harness.

A regulator pressure gauge should be in view of the user at all times. This gauge shows the cylinder pressure and reserve supply. During normal operation, the emergency bypass valve should be fully closed (turn clockwise for closing), and the regulator control valve to the main line should be fully opened (turn counterclockwise for opening) and locked in position by the locking device. This valve shuts off the automatic demand regulator if it fails or is damaged. It should be closed only after the emergency bypass has been opened. ONCE THE VALVES ARE SET IN THIS POSITION, THEY SHOULD NOT BE CHANGED UNLESS THE EMERGENCY BYPASS VALVE IS NEEDED. The air or oxygen supply is controlled by a main valve on the cylinder. (Open and close these valves with your fingers; do not use force.)

The operations described are intended for one brand of demand regulator equipment. Operations for other types of brands are similar, but the location of some of their parts may be different. This manual suggests these operations as a guide for all demand regulator equipment.

Donning the Facepiece (six-strap model)

Since facepieces for most breathing apparatus are applied in a similar manner, a step-by-step method of applying a six-strap model will be described only once and will be referred to throughout this manual. Head