TM 3-4240-212-14&P
Width................................................................. 17 1/4 in
chemically treated cloth in a tubular container. Rubbing
Depth................................................................. 10 1/8 In
the lenses with the cloth prevents fogging. Instructions for
Cubage.............................................................. 2.2 cu ft
use are printed on the containers.
Weights:
(4) M20 oxygen breathing apparatus hood. The
Breathing apparatus
rubber-coated cloth hood is worn over the facepiece to
without canisters.......................................... 13 lb
protect the head and neck of the wearer. An opening in
Regular canister ................................................ 4 1/2 lb
front is ringed with elastic material, which fits around the
Quick-starting canister ....................................... 4 3/4 lb
facepiece lenses and valve assembly to hold the hood in
Carrying case (empty) ....................................... 13 lb
place. The M20 hood is the only hood designed to be
Carrying case. breathing
used with the breathing apparatus.
apparatus, three
canisters, and
1-4.
Tabulated Data
accessories ................................................. 40 lb
All numerical data are approximate.
Life of canisters:
Carrying case:
Shelf life .............................
Indefinite
Length................................................................ 23 1/8 In
Useful life ...........................
Recommended for 45
minutes from the time
the canister begins to
generate oxygen
Section III. USE AND FUNCTIONING
with hood in atmospheres having high concentrations of
NOTE
chemical or biological agents may result in physiological
Users of the breathing apparatus should work in
reactions caused by absorption of the agent through the
pairs. One man can check on the other man's
skin in the head or neck areas. Since, at this time, there
elapsed time on a single canister and assist him
is no protective hood which can be used with the
if necessary.
breathing apparatus to provide impermeable protection to
the head and neck areas of the wearer, the breathing
WARNING
apparatus must not be used for chemical-biological
Do not use the breathing apparatus for
protection in atmospheres where the use of full
chemical-biological
agent
protection
in
impermeable protective clothing is required.
atmospheres where the use of full impermeable
protective clothing is required.
1-6.
Functioning
a. The breathing apparatus removes carbon dioxide
WARNING
and moisture from exhaled breath and generates oxygen
Do not use the breathing apparatus in an
to replace that consumed by the operator. Exhaled
explosive gas atmosphere.
exhalation valve in the facepiece valve assembly, and
1-5.
Use
through the exhalation breathing tube to the plunger valve
Since the wearer breathes only oxygen generated within
assembly The plunger valve assembly routes the exhaled
the canister, the breathing apparatus can safely be used
breath through the canister and into the breathing bag
to provide respiratory protection against irrespirable
b. As the exhaled breath passes through the
canister, moisture in the breath reacts with the chemical
oxygen-deficient atmospheres.
The hood presently
filling to form oxygen directly: A secondary reaction
issued with the breathing apparatus has no inner seal
between the carbon dioxide in exhaled breath and the
(such as that on the M3 toxicological agent protective
chemical filling forms water. The water, in turn, continues
hood) which can be used to provide an effective, vapor-
to react with the filling to form additional oxygen Once
proof seal with the M3 toxicological agent protective suit.
the generation of oxygen starts in the canister, it will
Also, the stitching holes in the seams of the M20 hood
continue as long as moisture and carbon dioxide
have not been sealed. Use of the breathing apparatus
Change 1
1-6