45 minutes. For your personnel protection you should
set the timer on the OBA for 30 minutes, allowing
15 minutes to leave the area and return to fresh air.
When in operation, the air within the apparatus is
continuously replenished with oxygen while the
chemicals in the canister remove exhaled carbon
dioxide (CO2) and water vapor. As a result of this
chemical action, the OBA wearer may survive and work
in a toxic atmosphere, such as a smoke-filled
compartment. With the facepiece and canister in place,
using the OBA forms a closed self-sustaining system.
For personnel having eyeglasses, a spectacle kit is
available for the installation of prescription lenses in the
When removing the candle cover, do not
remove the cotter pin while pulling the lanyard.
Removal of the cotter pin fires the candle and
starts generating oxygen. If that happens while
the copper foil is intact, internal pressure in the
canister will build up, causing the copper foil or
canister seam to rupture. Do not pull the cotter
pin until the canister is inserted in the OBA and
the bail assembly is up and locked.
Do not pull the breathing bag tab during normal
use because the oxygen in the bags will leak
into the atmosphere, causing loss of your
Never allow grease, oil, or water to enter the
neck of the canister. Any of these liquids may
cause a violent chemical reaction or explosion.
The chemicals contained in the canister are
injurious to skin and equipment.
The self-contained breathing apparatus (SCBA)
(fig. 12-6) is replacing the OBA throughout the Navy.
The units main components consist of a harness,
high-pressure bottle, pressure regulator, full-face mask,
and the high- and low-pressure hoses as shown below
High-pressure air cylinders are filled with compressed
grade D breathing air and then stored until needed. The
cylinders themselves are rechargeable, replacing the
need for additional canisters in the OBA system.
Figure 12-6.Self-contained breathing apparatus (SCBA).