STARTING THE CANISTER.- When you are ready to enter the contaminated area, start the canister in the following manner:

1. If your facepiece is in the standby position, put it on before starting the canister. Retighten the lower straps and retest your facepiece for a proper seal.

2. Unlock the bail assembly handle of the OBA by using both hands to depress the tabs from the bottom lock. Swing the handle upward until it snaps. Test the handle to see if it is locked by

Figure 6-20.-Airtightness of the facepiece.

lightly pushing the handle forward without depressing the tabs.

3. Pull the lanyard on the canister straight out and away from your body. This removes the cotter pin (fig. 6-2 1), fires the candle, and inflates the breathing bag with oxygen. After you pull the lanyard, always check to ensure that the cotter pin is still attached to the lanyard. A slight amount of harmless smoke maybe present in the facepiece while the candle is burning.

4. Now, test the tube connectors, canister, and breathing bags for tightness. While the candle is filling the breathing bag, depress the breathing bag at the pull tab with your left hand. Regrasp and seal off both breathing tubes with your right hand, while pressing against the right side of the breathing bag with your right elbow (fig. 6-22). The bag must be compressed at the pull tab so that the relief valve does not vent during this test. The bag must remain inflated; otherwise, there may be a leak in the OBA, which you must correct before you use the OBA.

5. Breathe normally. The chemical reaction of the canister will generate more oxygen than you require. If too much oxygen is produced, the extra oxygen will be vented automatically by the relief valve in the bag when the bag reaches full capacity. A manual relief pull tab on the valve (fig. 6-23) is provided in case the valve sticks in the closed position during a long period of storage. DO NOT pull the breathing bag tab

Figure 6-21 .-Checking for the cotter pin.

Figure 6-22.-Testing the OBA.

during normal use. If you do, you will vent your breathing oxygen from the breathing bag to the atmosphere.

In the event of a malfunction of the candle, you can activate the canister manually. The manual starting of the canister is not recommended. The procedures listed here are to be used only when the chlorate candle has misfired and sufficient time is available to start the canister manually, or if there is a shortage of available canisters. Under no circumstances should you save

Figure 6-23.-Manual relief valve tab.

the chlorate candle to use for an emergency exit of the space. Such practice is dangerous, and the candles have been known to misfire.

You must be in a clean atmosphere when manually starting the canister. Use the following procedures:

1. Work one finger under the edge of your facepiece, stretching the mask slightly to break the seal.

2. Inhale while grasping and squeezing both breathing tubes with your other hand. This will allow you to draw external air from outside the facepiece.

3.Release the breathing tubes, remove your finger to reseal the mask, and exhale into the facepiece.

4.Continue this cycle until your breathing bag is fully inflated. Exhaust the air in the breathing bag by exerting pressure on the right-hand side until the bag on the right is deflated. In this process, your moist breath passes through the canister to start the chemical reaction. One filling of the bag is not usually sufficient to fully activate the canister

5. Repeat steps 1 through 4 to reinflate and deflate the breathing bag at least five times. Now, without gloves, cautiously feel the bottom of the canister. If the entire bottom of the canister is warm, oxygen is being generated. The apparatus is then ready for setting the timer and for the operational check. If the canister is not warm, repeat steps 1 through 4. In cooler temperatures, several cycles of inflation and deflation of the bag may be required to start oxygen production.