137 

Federal Aviation Administration, DOT 

§ 121.337 

period for at least 10 percent of the pas-
senger cabin occupants. 

(2) When an airplane is operated at 

flight altitudes up to and including 
flight level 250 and cannot descend 
safely to a flight altitude of 14,000 feet 
within four minutes, or when an air-
plane is operated at flight altitudes 
above flight level 250, oxygen must be 
available at the rate prescribed by this 
part for not less than 10 percent of the 
passenger cabin occupants for the en-
tire flight after cabin depressurization, 
at cabin pressure altitudes above 10,000 
feet up to and including 14,000 feet and, 
as applicable, to allow compliance with 
§ 121.329(c) (2) and (3), except that there 
must be not less than a 10-minute sup-
ply for the passenger cabin occupants. 

(3) For first-aid treatment of occu-

pants who for physiological reasons 
might require undiluted oxygen fol-
lowing descent from cabin pressure al-
titudes above flight level 250, a supply 
of oxygen in accordance with the re-
quirements of § 25.1443(d) must be pro-
vided for two percent of the occupants 
for the entire flight after cabin depres-
surization at cabin pressure altitudes 
above 8,000 feet, but in no case to less 
than one person. An appropriate num-
ber of acceptable dispensing units, but 
in no case less than two, must be pro-
vided, with a means for the cabin at-
tendants to use this supply. 

(f) 

Passenger briefing. 

Before flight is 

conducted above flight level 250, a 
crewmember shall instruct the pas-
sengers on the necessity of using oxy-
gen in the event of cabin depressuriza-
tion and shall point out to them the lo-
cation and demonstrate the use of the 
oxygen-dispensing equipment. 

[Doc. No. 6258, 29 FR 19205, Dec. 31, 1964, as 
amended by Amdt. 121–11, 30 FR 12466, Sept. 
30, 1965; Amdt. 121–132, 41 FR 55475, Dec. 20, 
1976; Amdt. 121–262, 62 FR 13256, Mar. 19, 1997; 
62 FR 15570, Apr. 1, 1997; Amdt. 121–306, 69 FR 
62789, Oct. 27, 2004; Amdt. 121–383, 85 FR 16900, 
Mar. 25, 2020] 

§ 121.335 Equipment standards. 

(a) 

Reciprocating engine powered air-

planes. 

The oxygen apparatus, the min-

imum rates of oxygen flow, and the 
supply of oxygen necessary to comply 
with § 121.327 must meet the standards 
established in section 4b.651 of the Civil 
Air Regulations as in effect on July 20, 

1950, except that if the certificate hold-
er shows full compliance with those 
standards to be impracticable, the Ad-
ministrator may authorize any change 
in those standards that he finds will 
provide an equivalent level of safety. 

(b) 

Turbine engine powered airplanes. 

The oxygen apparatus, the minimum 
rate of oxygen flow, and the supply of 
oxygen necessary to comply with 
§§ 121.329 and 121.333 must meet the 
standards established in section 4b.651 
of the Civil Air Regulations as in effect 
on September 1, 1958, except that if the 
certificate holder shows full compli-
ance with those standards to be im-
practicable, the Administrator may au-
thorize any changes in those standards 
that he finds will provide an equivalent 
level of safety. 

§ 121.337 Protective breathing equip-

ment. 

(a) The certificate holder shall fur-

nish approved protective breathing 
equipment (PBE) meeting the equip-
ment, breathing gas, and communica-
tion requirements contained in para-
graph (b) of this section. 

(b) 

Pressurized and nonpressurized 

cabin airplanes. 

Except as provided in 

paragraph (f) of this section, no person 
may operate an airplane unless protec-
tive breathing equipment meeting the 
requirements of this section is provided 
as follows: 

(1) 

General. 

The equipment must pro-

tect the flightcrew from the effects of 
smoke, carbon dioxide or other harmful 
gases or an oxygen deficient environ-
ment caused by other than an airplane 
depressurization while on flight deck 
duty and must protect crewmembers 
from the above effects while combat-
ting fires on board the airplane. 

(2) The equipment must be inspected 

regularly in accordance with inspec-
tion guidelines and the inspection peri-
ods established by the equipment man-
ufacturer to ensure its condition for 
continued serviceability and imme-
diate readiness to perform its intended 
emergency purposes. The inspection pe-
riods may be changed upon a showing 
by the certificate holder that the 
changes would provide an equivalent 
level of safety. 

(3) That part of the equipment pro-

tecting the eyes must not impair the