460 

14 CFR Ch. I (1–1–14 Edition) 

§ 25.831 

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 
supplied to other compartments and 
areas: 

(1) The flight crew compartment. 
(2) Crewmember compartments and 

areas other than the flight crew com-
partment unless the crewmember com-
partment or area is ventilated by air 
interchange with other compartments 
or areas under all operating conditions. 

(f) Means to enable the flight crew to 

control the temperature and quantity 
of ventilating air supplied to the flight 
crew compartment independently of 
the temperature and quantity of ven-
tilating air supplied to other compart-
ments are not required if all of the fol-
lowing conditions are met: 

(1) The total volume of the flight 

crew and passenger compartments is 
800 cubic feet or less. 

(2) The air inlets and passages for air 

to flow between flight crew and pas-
senger compartments are arranged to 
provide compartment temperatures 
within 5 degrees F. of each other and 
adequate ventilation to occupants in 
both compartments. 

(3) The temperature and ventilation 

controls are accessible to the flight 
crew. 

(g) The exposure time at any given 

temperature must not exceed the val-
ues shown in the following graph after 
any improbable failure condition. 

VerDate Mar<15>2010 

10:12 Mar 18, 2014

Jkt 232046

PO 00000

Frm 00470

Fmt 8010

Sfmt 8010

Y:\SGML\232046.XXX

232046

pmangrum on DSK3VPTVN1PROD with CFR