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2.4 Theory of Operation
1.) When the Neck Strap is pulled from the Base, the oxygen valve is activated.
Oxygen continuously flows from the cylinder to the Breathing Bag at a rate if
1.5 liters per minute.
2.) During the first inhalation, and when the Bag flattens, the Demand Regulator is
activated and increases the oxygen flow from 1.5 liters per minute up to as
much as 100 liters per minute.
3.) During inhalation, oxygen is pulled from the bag through the Scrubber and into
the Mouthpiece.
4.) During exhalation, carbon dioxide laden air is exhaled into the Mouthpiece
through the Scrubber and into the Breathing Bag. During inhalation and
exhalation, the carbon dioxide is being absorbed by the Lithium Hydroxide
scrubber.
5.) Sometimes during low work rates, the oxygen controller will supply more
oxygen than the user can consume and excess gas exits the Relief Valve.
The starting of the oxygen flow, the increased flow rate during high work rates
and the occasional exhausting of gas through the Relief Valve all occur
automatically, the user needs only to breathe.
2.5 Specifications
Duration:
10 minutes, NIOSH / MSHA
Dimensions:
3.0 x 6.5 x 7.2 (in)
7.6 x 16.5 x 18.3 (cm)
Weight of breathing apparatus:
2.0 lbs (0.9 kg)
Weight of breathing apparatus with case:
3.30 lbs (1.5 kg)
Minimum storage temperature:
10 degrees F (-12º C)
Maximum storage temperature:
140 degrees F (60º C)
Storage at temperatures above 140 degrees F (60º C) for short periods will not
adversely affect the M-20. In an emergency, don the M-20 regardless of
temperature.
Scrubber life is limited to one escape event or one oxygen charge
Mandatory factory service is required after 10 years if stored and 5 years if
M-20 is carried. End of service life is 15 years.
