SETTING THE TIMER.- To set the timer, grasp the knob on the timer. Turn the knob clockwise to 60 minutes, and then turn it counterclockwise to 30 minutes. By setting the timer to 60 first, you fully wind the alarm bell spring. When 30 minutes have expired, the warning bell will sound continuously for 10 or more seconds. When you have set the timer, you are ready to enter a hazardous atmosphere.

REMOVING AN UNUSED CANISTER.- If the canister's copper-foil seal has not been punctured, remove the canister by placing one hand on the bottom of the canister and pulling the canister releasing strap. You do not need to wear gloves in this situation. The handle must also be in the load and standby positions.

Once the canister is removed, protect the copper-foil seal by installing one of the spare aluminum caps that are provided for this purpose.

REMOVING A USED CANISTER.- When you remove a hot canister, you need to protect your hands with approved protective gloves.

Once the canister has been used, remove the facepiece and put it over your head in the standby position. Then, unlock the handle from the operation position and swing it down to the load and standby positions.

Next, unfasten the waist strap, spread your feet apart and lean the upper part of your body slightly forward. To release the used canister, pull the canister release strap (fig. 6-24). The canister will drop out of the apparatus (fig, 6-25). Drop the canister ONLY on a clean, dry deck.

You need to be careful when you remove used canisters from the OBA. They are hot, and the chemicals inside of the canister can cause serious chemical burns if they get on your skin. The chemicals are similar to caustic soda, also known as lye. Normally, you will not have chemicals spilling out of the canister, but there is always the possibility. Finally, the chemicals will cause a violent explosion if they come into contact with a petroleum-base substance.

DISPOSAL OF USED CANISTERS.- You must dispose of an OBA quick-starting canister as soon as possible after it has been used or when the copper-foil seal has been punctured.

If your ship is more than 25 nautical miles from shore, you may throw the canister overboard. To dispose of the canister in this manner, first obtain permission from the officer of the deck. Once permission has been granted, ensure that the canister cap is removed and the copperfoil seal is fully punctured. This will allow water to enter the canister. DO NOT puncture holes

Figure 6-24.-Releasing the canister.

Figure 6-25.-Dropping the canister.

in the bottom or sides of the canister. Make sure there is no oil in the water. Then throw the canister overboard. If oil gets inside of the canister, a violent explosion will occur.

If you are within 25 nautical miles of shore, do not throw the canister overboard. Instead, let it cool down for at least 30 minutes. (If a canister was not used, but the copper-foil seal has been punctured, place the canister in a clean bucket. Light off the canister and let it set for 15 minutes to cool.) When the canister is cool enough to handle, place a new metal cap, NSN 4240-00-089-7963, on the neck to cover the punctured copper-foil seal. Then double wrap the canister in a poly bag, NSN 8105-00-2998532, or its equivalent. The wrapped canister should then be stored in a dry, oil-free area until it can be disposed of at sea or turned over to a shore facility for disposal.

When the ship is in port, contact the department ashore that is responsible for hazardous waste. Make arrangements with that department to turn all canisters over to them for disposal.

REMOVING THE OBA.- Remove the OBA in the following manner:

1. Remove the facepiece by releasing the head straps at the buckles with your fingertips before pulling the headpiece off. If the canister is still in the OBA, place the facepiece over your head

in the standby position and remove the canister. NEVER remove the OBA with a canister in place.

2. If the facepiece is in standby position, you should remove it and let it hang in front of the OBA.

3. Loosen the waist strap, then unhook it.

4. Loosen the shoulder straps and unhook the harness at the upper corners of the breastplate assembly. Grasp the facepiece and operating handle with one hand and the shoulder harness (preferably at the D-ring connector) with your other hand. Lift the OBA over your head.

5. If the OBA is wet or moist, wipe it down.

6. Always clean the outside body of the OBA after each use with a mild solution of soap and warm water.

7. Disinfect the inside of the facepiece. Mix the disinfectant (NSN 95-6840-00-526-1129) as stated on the container label. Use a sponge that is moist, but not dripping, with the disinfectant solution.

OBA Equipment Stowage

Before stowing the OBA, the facepiece should be protected to prevent scratches and abrasions. All OBA equipment and canisters must be stored in a cool, dry place. The life of an OBA will be

Figure 6-26.-OBA storage locker.

lengthened if it is stored under these conditions. The term cool denotes temperatures ranging from above freezing to 110F (43C) when storage is out of direct sunlight. The term dry usually denotes a storage area where condensation does not come in contact with the equipment.

The only places the OBA should be stowed onboard ship are in repair lockers or in OBA lockers (fig. 6-26). These lockers have provisions for stowing the OBA in a flat position. You should ensure that the facepiece is properly protected to prevent scratching or scarring of the lens. The canisters should be stowed with the concave side down. Additional information on cleaning, inspecting, and testing of the type A-4 OBA can be found in the Naval Ships' Technical Manual, chapter 079, volume 2.