360 

14 CFR Ch. I (1–1–24 Edition) 

§ 25.1441 

volume of 30 liters per minute BTPD. 
The equipment and system must be de-
signed to prevent any inward leakage 
to the inside of the device and prevent 
any outward leakage causing signifi-
cant increase in the oxygen content of 
the local ambient atmosphere. If a de-
mand oxygen system is used, a supply 
of 300 liters of free oxygen at 70 

°

F. and 

760 mm. Hg. pressure is considered to 
be of 15-minute duration at the pre-
scribed altitude and minute volume. If 
a continuous flow open circuit protec-
tive breathing system is used, a flow 
rate of 60 liters per minute at 8,000 feet 
(45 liters per minute at sea level) and a 
supply of 600 liters of free oxygen at 70 

°

F. and 760 mm. Hg. pressure is consid-

ered to be of 15-minute duration at the 
prescribed altitude and minute volume. 
Continuous flow systems must not in-
crease the ambient oxygen content of 
the local atmosphere above that of de-
mand systems. BTPD refers to body 
temperature conditions (that is, 37 

°

C., 

at ambient pressure, dry). 

(6) The equipment must meet the re-

quirements of § 25.1441. 

[Doc. No. FAA–2002–13859, 69 FR 40528, July 2, 
2004] 

§ 25.1441

Oxygen equipment and sup-

ply. 

(a) If certification with supplemental 

oxygen equipment is requested, the 
equipment must meet the requirements 
of this section and §§ 25.1443 through 
25.1453. 

(b) The oxygen system must be free 

from hazards in itself, in its method of 
operation, and in its effect upon other 
components. 

(c) There must be a means to allow 

the crew to readily determine, during 
flight, the quantity of oxygen available 
in each source of supply. 

(d) The oxygen flow rate and the oxy-

gen equipment for airplanes for which 
certification for operation above 40,000 
feet is requested must be approved. 

§ 25.1443

Minimum mass flow of sup-

plemental oxygen. 

(a) If continuous flow equipment is 

installed for use by flight crew-
members, the minimum mass flow of 
supplemental oxygen required for each 
crewmember may not be less than the 
flow required to maintain, during in-

spiration, a mean tracheal oxygen par-
tial pressure of 149 mm. Hg. when 
breathing 15 liters per minute, BTPS, 
and with a maximum tidal volume of 
700 cc. with a constant time interval 
between respirations. 

(b) If demand equipment is installed 

for use by flight crewmembers, the 
minimum mass flow of supplemental 
oxygen required for each crewmember 
may not be less than the flow required 
to maintain, during inspiration, a 
mean tracheal oxygen partial pressure 
of 122 mm. Hg., up to and including a 
cabin pressure altitude of 35,000 feet, 
and 95 percent oxygen between cabin 
pressure altitudes of 35,000 and 40,000 
feet, when breathing 20 liters per 
minute BTPS. In addition, there must 
be means to allow the crew to use undi-
luted oxygen at their discretion. 

(c) For passengers and cabin attend-

ants, the minimum mass flow of sup-
plemental oxygen required for each 
person at various cabin pressure alti-
tudes may not be less than the flow re-
quired to maintain, during inspiration 
and while using the oxygen equipment 
(including masks) provided, the fol-
lowing mean tracheal oxygen partial 
pressures: 

(1) At cabin pressure altitudes above 

10,000 feet up to and including 18,500 
feet, a mean tracheal oxygen partial 
pressure of 100 mm. Hg. when breathing 
15 liters per minute, BTPS, and with a 
tidal volume of 700 cc. with a constant 
time interval between respirations. 

(2) At cabin pressure altitudes above 

18,500 feet up to and including 40,000 
feet, a mean tracheal oxygen partial 
pressure of 83.8 mm. Hg. when breath-
ing 30 liters per minute, BTPS, and 
with a tidal volume of 1,100 cc. with a 
constant time interval between res-
pirations. 

(d) If first-aid oxygen equipment is 

installed, the minimum mass flow of 
oxygen to each user may not be less 
than four liters per minute, STPD. 
However, there may be a means to de-
crease this flow to not less than two li-
ters per minute, STPD, at any cabin al-
titude. The quantity of oxygen re-
quired is based upon an average flow 
rate of three liters per minute per per-
son for whom first-aid oxygen is re-
quired. 

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