300 

14 CFR Ch. I (1–1–24 Edition) 

§ 25.820 

following loss of normal electrical 
power generating system. 

(c) There must be an aural emer-

gency alarm system, audible during 
normal and emergency conditions, to 
enable crewmembers on the flight deck 
and at each required floor level emer-
gency exit to alert occupants of each 
lower deck service compartment of an 
emergency situation. 

(d) There must be a means, readily 

detectable by occupants of each lower 
deck service compartment, that indi-
cates when seat belts should be fas-
tened. 

(e) If a public address system is in-

stalled in the airplane, speakers must 
be provided in each lower deck service 
compartment. 

(f) For each occupant permitted in a 

lower deck service compartment, there 
must be a forward or aft facing seat 
which meets the requirements of 
§ 25.785(d), and must be able to with-
stand maximum flight loads when oc-
cupied. 

(g) For each powered lift system in-

stalled between a lower deck service 
compartment and the main deck for 
the carriage of persons or equipment, 
or both, the system must meet the fol-
lowing requirements: 

(1) Each lift control switch outside 

the lift, except emergency stop but-
tons, must be designed to prevent the 
activation of the life if the lift door, or 
the hatch required by paragraph (g)(3) 
of this section, or both are open. 

(2) An emergency stop button, that 

when activated will immediately stop 
the lift, must be installed within the 
lift and at each entrance to the lift. 

(3) There must be a hatch capable of 

being used for evacuating persons from 
the lift that is openable from inside 
and outside the lift without tools, with 
the lift in any position. 

[Amdt. 25–53, 45 FR 41593, June 19, 1980; 45 FR 
43154, June 26, 1980; Amdt. 25–110; 68 FR 36883, 
June 19, 2003] 

§ 25.820

Lavatory doors. 

All lavatory doors must be designed 

to preclude anyone from becoming 
trapped inside the lavatory. If a lock-
ing mechanism is installed, it must be 

capable of being unlocked from the 
outside without the aid of special tools. 

[Doc. No. 2003–14193, 69 FR 24502, May 3, 2004] 

V

ENTILATION AND

H

EATING

 

§ 25.831

Ventilation. 

(a) Under normal operating condi-

tions and in the event of any probable 
failure conditions of any system which 
would adversely affect the ventilating 
air, the ventilation system must be de-
signed to provide a sufficient amount 
of uncontaminated air to enable the 
crewmembers to perform their duties 
without undue discomfort or fatigue 
and to provide reasonable passenger 
comfort. For normal operating condi-
tions, the ventilation system must be 
designed to provide each occupant with 
an airflow containing at least 0.55 
pounds of fresh air per minute. 

(b) Crew and passenger compartment 

air must be free from harmful or haz-
ardous concentrations of gases or va-
pors. In meeting this requirement, the 
following apply: 

(1) Carbon monoxide concentrations 

in excess of 1 part in 20,000 parts of air 
are considered hazardous. For test pur-
poses, any acceptable carbon monoxide 
detection method may be used. 

(2) Carbon dioxide concentration dur-

ing flight must be shown not to exceed 
0.5 percent by volume (sea level equiva-
lent) in compartments normally occu-
pied by passengers or crewmembers. 

(c) There must be provisions made to 

ensure that the conditions prescribed 
in paragraph (b) of this section are met 
after reasonably probable failures or 
malfunctioning of the ventilating, 
heating, pressurization, or other sys-
tems and equipment. 

(d) If accumulation of hazardous 

quantities of smoke in the cockpit area 
is reasonably probable, smoke evacu-
ation must be readily accomplished, 
starting with full pressurization and 
without depressurizing beyond safe 
limits. 

(e) Except as provided in paragraph 

(f) of this section, means must be pro-
vided to enable the occupants of the 
following compartments and areas to 
control the temperature and quantity 
of ventilating air supplied to their 
compartment or area independently of 
the temperature and quantity of air 

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