OXYGEN BREATHING APPARATUS

The type A-4 oxygen breathing apparatus (OBA) is used throughout the Navy. The OBA is an entirely self-contained breathing apparatus. It enables the wearer to breathe independently of the outside atmosphere. It produces its own oxygen and allows the wearer to enter compartments, voids or tanks that contain smoke, dust, or fire, or those that have a low oxygen content.

Major OBA Components

You will be required to wear, operate, and maintain in perfect operating condition the type A-4 OBA. To do so, you must know the various components of the OBA and their purposes. Figure 6-1 shows the components and identifies them. As you read about the various components, refer to this figure as well as to those pertaining to the individual components.

FACEPIECE.- The facepiece (fig. 6-2) contains the eyepiece, the speaking diaphragm, and the head straps. The eyepiece is a one-piece clear lens. A spectacle kit is provided that may be installed in the facepiece. Corrective lenses may be installed in the kit for individuals who require glasses. However, once the lenses are installed, only the person that the lenses are made for can

Figure 6-1.-Components of the OBA.

Figure 6-3.-Breathing tubes.

tubes to control the oxygen. The breathing bag contains the oxygen that is generated by the canister for you to breathe. One breathing tube transports the oxygen from the breathing bag to the facepiece (fig. 6-3); the other transports the exhaled air back to the canister. Both tubes are made of corrugated rubber. They control the flow of air and help cool the air for your comfort when you wear the OBA. The tubes are a quick-disconnect type. The tube couplings are color coded, and the supply tube is of a different size than the exhaust tube. This prevents the possibility of connecting the tubes to the wrong couplings.

TIMER.- The timer (figs. 6-1 and 6-4) is located so that you can check the amount of

Figure 6-2.-Facepiece with spectacle kit installed.

use that spectacle kit. The speaking diaphragm allows you to talk to others and to use communication devices such as sound-powered telephones. The head straps hold the facepiece snug against your face. If the straps are adjusted properly, no outside gases can get inside of the facepiece.

BREATHING BAG AND TUBES.- The OBA has a breathing bag and two breathing

_{Figure 6-4.-Timer.}

time remaining as you go about your duties. The timer's bells are made to ring for 8-10 seconds continuously.