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4
AIR QUALITY IN EMERGENCY SITUATIONS
Chapter 2 describes the physical factors that
influence airliner cabin air quality under normal
operating conditions, and Chapter 3 describes the
federal regulations and industry operating procedures
that bear on air quality. This chapter focuses on the
effects of emergency situations on cabin air quality.
Two in-flight emergency situations affect cabin air
quality: fire and cabin Repressurization. Not only can
fire lead to deterioration of the structural integrity
of the aircraft and its ability to remain in controlled
flight, but the resulting smoke and toxic combustion
products and ultimately the fire itself constitute
direct hazards to passengers and crew. The main threat
to passengers in sudden Repressurization is hypoxia.
ONBOARD FIRES
Providing protection from fire in airliners is a
complicated matter. Cabin interiors are furnished and
lined with potentially flammable materials, and
passengers are tightly packed in a relatively small,
confined enclosure. Inaccessible compartments contain
potential ignition sources and combustible materials,
and wing tanks carry thousands of gallons of highly
flammable aviation fuel. Given these conditions, the
average of 32 deaths a year from the effects of fire
involving U.S. air carriers between 1965 and 1979 might
seem remarkably low, compared with the figures on other
modes of transport. \4 But it is a mayor concern. An
estimated 15% of all deaths in domestic air carrier
accidents during that period have been attributed to the
effects of fire. 15
91
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An analysis of air transport accidents in North
Atlantic Treaty Organization (NATO) countries between
1964 and 1975 revealed (when such information could be
determined) that injuries and deaths were due primarily
to the postcrash effects of fire, smoke, and toxic fumes
and only secondarily to crash impact itnelf.17 The
aircraft used in NATO countries are largely of American
manufacture and meet American standards, so data on
accidents in these countries should be considered with
the American data; that increases the apparent incidence
of fire-related death.
Three accidents have played an especially prominent
role in increasing awareness of the importance of smoke
and toxic fumes:
· In 1973, a passenger aboard a Varig Airlines flight
(B-707) reported smoke in the lavatory shortly before
the scheduled landing at Orly Airport, near Paris.
Within 6 min. thick black smoke filled the cabin and
cockpit. Unable to see their instruments, the pilots
opened their side windows and made a forced landing in a
field 4 miles from the airport. Of 135 occupants, 10
crew members and one passenger survived, all in the
cockpit. The remaining 124 died from asphyxiation or
the effects of toxic gases.4 1°
· In 1980, a Saudi Airlines aircraft (L-1011)
with 301 passengers and crew on board made an emergency
landing after reporting an in-flight fire. The aircraft
landed and taxied normally for several minutes before
coming to a stop. None of the doors was opened, and all
on board died.
· In 1983, a successful landing was made in Greater
Cincinnati Airport after an in-flight fire aboard an Air
Canada flight (DC-9~. Of the 46 occupants, 23 were
overcome by smoke and toxic fumes, could not leave the
airplane, and died in the ensuing fire.~°
These incidents are part of the ample evidence that
many passengers in crashes or unplanned landings in
which fire is involved are unable to escape from the
aircraft, even though they have not sustained injuries
that would prevent escape. There is a strong presumption
that these passengers have succumbed to smoke or toxic
fumes in the cabin. The conditions of air quality during
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fire emergencies are examined here, with appropriate
measures that might be taken to prevent or ameliorate
these conditions so as to increase the likelihood of
survival and escape.
INHIBITING IGNITION
wayside
Postcrash fires generally originate in one of six
.
From release of fuel caused by wing separation
during impact-survivable accidents.
· From release of fuel from damaged fuel tacks or
fuel lines during impact-survivable accidents.
· From fuel tank explosions caused by external
heating and other ignition sources in the crash.
~ From ignition of materials in the cabin during
the crash.
· In the propulsion system.
· In the landing gear system.
It is generally agreed that ignition of Jet fuel
constitutes the greatest potential danger in aircraft
crashes.lS In accidents in which large quantities of
fuel are released and ignited (pool fires) and the
integrity of the fuselage is damaged to the extent that
mayor portions of the cabin are directly subjected to
the fuel fire, the dominance of the fuel fire is clear.
But even when the fuselage remains relatively intact,
the radiant energy impinging on the cabin through the
window ports from the flame of the pool fire is
sufficient to ignite many materials.!' Obviously,
prevention of crashes and resulting fires is a major
concern of the airline industry and the Federal Aviation
Administration (FAA), but discussion of approaches to
prevention is beyond the scope of this report.
Major fuel fires are very rare, and most incidents
involving fire on aircraft involve less catastrophic
situations. Although they are of considerable interest,
little information is available on the progress of major
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past in-flight fires. However, typical origins of in-
flight fires have been characterized.12 Typical origins
in the cockpit include malfunction of the electric
equipment and oxygen supply system. Origins of fires in
the cabin include failure in the oxygen supply system,
liquid fuel spills, short circuits, matches, lighters,
cigarettes and cigars, and carry-on luggage. The food
service galley is a common source of fires, with origins
including ovens and oven exhaust systems, electric
equipment, food waste storage, and the oxygen system.
The lavatory is one of the few areas of the cabin where,
because it is enclosed and has separate ventilation, a
fire can go undetected until it reaches a dangerous
magnitude. Although fires resulting from smoking in the
lavatories have been of considerable concern, it appears
that light wiring, speaker transformers, fluorescent-
light ballasts, water heaters, and the flushing motor
are more likely sources of serious lavatory fires. i2 In
cargo compartments, fire sources include short circuits
and cargo. Movie projectors, electric motors, and
control equipment are possible causes of attic fires.
Unpressurized landing gear wells--containing hydraulic
fuel lines, electric controls and devices, and
water-line heaters--can be sources of fire. Finally,
electric equipment and avionic equipment are potential
sources of electric fires.
Table 1-9 summarizes the incidents involving smoke
or fumes in aircraft cabins or cockpits that have been
recorded in the FAA Civil Aeromedical Institute (CAMI)
Cabin Safety Data Bank. About 20 incidents are reported
in a typical year, including about 13 emergency landings.
An analysis of a different set of data, reports by Part
121 and Part 135 air carriers to FAA between 1980 and
1985 (summarized in Table 1-8), reveals that--of 138
incidents of fire, explosion, smoke, or related
odors--68 involved mechanical failures, 25 involved
electric malfunctions, 15 were galley incidents (of
which eight involved spills of food or other material in
the oven), 10 were lavatory fires (of which five were in
waste-paper receptacles or otherwise involved paper
products), eight were in the cabin (of which five
involved cigarettes or lighters), and eight were
categorized as "other" or "undetermined.' Strict
adherence to servicing codes and careful examination of
such codes whenever a fire results from malfunction are
required. Similarly, each crew-related fire, especially
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those involving cooking, should receive careful scrutiny
from the point of view of equipment reliability,
procedural safety, and crew performance. In large
measure, the enforcement activities of FAA and the
review and recommendation procedures of the National
Transportation Safety Board described in Chapter 3 are
intended to accomplish these aims.
MATERIALS TESTING AND SELECTION
Failing prevention or immediate extinguishing of
fire, it becomes essential to decrease the rate of flame
propagation and production of toxic gas through
appropriate selection of structural and decorative
materials in the aircraft. The mayor regulatory efforts
to date have been directed toward selection of minimally
flammable materials for incorporation into the aircraft
cabin and cockpit, in accordance with fire testing
procedures noted in the Federal Aviation Regulations.5
On October 26, 1984, FAA published new standards
that would substantially reduce the flammability of foam
seat cushions; 20 transport aircraft seat cushions
must meet these new standards by November 26, 1987.
They require exposure of specimens of seat back and
bottom cushions over a limited area to a burner with
temperature and heat flux typical of cabin fire. The
test specifications require that the specimens simulate
the intended seat configuration and allow for the burning
interaction of upholstery cover, fire blocking layer,
and foam cushion material.~4 Criteria for acceptance
consist of 10% allowable weight loss, burn length of 17
in., and performance essentially matching that attained
by two benchmark materials.
On August 8, 1984, FAA announced proposed rules to
upgrade the fire safety standards for cargo or baggage
compartments in transport aircraft.19 FAA conducted
full-scale fire tests to investigate the resistance of
cargo liners to flame penetration for both compartments
to which crew members have access and in which fire
suppression systems are required (class C compartments)
and smaller compartments without access, which are
designed for fire control by oxygen starvation (class D
compartments). The main conclusion drawn from the
testing results was that a more realistic and severe
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test requirement was needed for cargo liners used in
both class C and class D cargo compartments. The new
fire test method, which measures breakthrough resistance
of cargo liners, applies the maximal heat flux and
temperature measured during full-acale tests under
realistic ceiling and sidewall liner orientation, i.e.,
both vertical and horizontal. Criteria for acceptance
are absence of flame penetration of ceiling and sidewall
specimens and temperature above the ceiling specimen not
exceeding 400°F.
In 1980, the FAA Special Aviation Fire and Explosion
Reduction (SAFER) Committee recommended a specific fire
scenario for FAA to use in full-scale tests and expedited
the development and evaluation of the Ohio State
University (OSU) rate-of-heat-release apparatus as the
potential standardized test for materials.25 On
April 16, 1985, after full-scale tests, FAA announced a
notice of proposed rule-making (NPRM 85-10) establishing
new fire test criteria for type certification of
transport aircraft that would apply to cabin interiors
of all newly manufactured aircraft and all other aircraft
that were type-certified after 1958 .22 In full-scale
tests, various interior panel materials were subjected
to situations simulating an external fuel pool fire with
an open door, and the results were correlated with
performance with the OSU test apparatus.9 A panel of
phenolic-fiberglass, a state-of-the-art composite used
in some applications in aircraft interiors, was used as
a benchmark. It added approximately 2 min to
survivability, compared with other available panels
studied. Criteria of 65 kW/m2 for peak heat release
rate and 65 kW-min/m2 for total heat release in 2 min
were established in accordance with the performance of
this benchmark panel.
The Aerospace Industries Association of America
(AIA), representing the airframe manufacturers, appears
to have legitimate concern about the ability of the
proposed NPRM 85-10 to discriminate adequately and
consistently between acknowledged inferior products and
molded interior components with known improved fire-
resistant characteristics.2 The proposed alternative
standardized testing, advocated by AIAl, so
discriminates, but permits use of state-of-the-art
material for aircraft interior walls, ceilings, and
other components that is (from a fire-resistance
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standpoint) only one-tenth as good as newer material,
which still needs development before it can be
satisfactorily used. Without some regulatory action or
impetus, the use of these less developed but safer
materials could be delayed until the next century.
Notwithstanding a potentially adverse economic impact on
airframe manufacturers, government-regulators and
enforcers, airline operators, and ultimately consumer-
passengers, the Committee feels (with respect to all the
topics under consideration here) that improved comfort
and safety deserve consideration, despite the extra time
that might be required in fine-tuning the product to
ensure its timely incorporation into some existing and
next-generation aircraft.
In general, the FAA program on flammability testing
is excellent, and its research efforts to improve
testing are appropriate and valuable. The Committee
feels that continuing research is also needed in
materials development. Although F. M standards are met
by currently available materials, other materials, if
developed further, would far exceed current standards
and would substantially increase fire protection in
aircraft. Such organizations as AIA or a similarly
constituted organization of airframe manufacturers
should be strongly encouraged to initiate or support
programs in this field.
The Secretary of Transportation is charged under the
Federal Aviation Act with responsibility for regulating
air commerce in such a manner as best to promote both
its development and its safety, but the Committee
believes that passenger safety must be paramount.
Because of the extreme hazard presented by fire and the
associated smoke and noxious and toxic combustion
products, minimization of fire and fumes should be of
highest priority. In support of the belief that a
materials development program should be encouraged, we
cite the example of the National Aeronautics and Space
Administration's response to the 1967 pad fire. A few
simple guidelines were developed for material replacement
as noted in Table 4-1, and a keyed index system was
initiated. The latter consisted of an index of every
nonmetallic component or individual item considered for
use in spacecraft or related equipment keyed to test
results for a variety of atmospheric conditions, such as
odor? toxicity, total emission of organic substances,
and various fire tests.
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TABLE 4-1
NASA Guidelines for Selection
of Replacement Materialsa
Replace all materials that burn in 100% oxygen
(3.~-16.5 psia) with nonflammable substitutes.
Material substitution may not affect mission
function.
B. All products that cannot be manufactured from
nonflammable materials are to be covered with
an insulating, nonflammable coating to prevent
the flammable substrate from being affected by
heat and fire for a specified period.
If A and B cannot be accomplished in a timely
fashion, institute an R&D program to achieve
those aims.
D. Provide a measure of fire control by the
arrangement of materials in the spacecraft.
Potential flame paths can be interrupted by
separating from each other items that have some
propensity to burn, thus creating "fire breaks."
a Data from M. I. Radnofsky (personal communication).
SMOKE DETECTION AND FIREFIGHTING
On March 29, 1985, FAA added ~ new paragraph to the
Part 121 regulations to provide thatch
.
Each lavatory and galley in passenger-carrying
airplanes be equipped with a smoke detector system or
equivalent that provides a warning light in the cockpit
or an audible warning in the passenger cabin that would
be readily detected by a cabin attendant.
· Each lavatory be equipped with a built-in
automatic fire extinguisher for each disposal receptacle
for towels, paper, or waste in the lavatory.
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Smoke detectors are to be installed by October 26,
1986, and automatic fire extinguishers, by April 29,
1987. The rifle also increases the number of hand-
operated fire extinguishers that must be carried and
provides that at least two must contain Halon 1211
(bromochlorodifluoromethane) or equivalent as the
extinguishing agent.
On October 10, 1985, FAA announced a proposed
addition to the Part 121 regulations to require portable
breathing equipment for at least one flight-attendant
station in each passenger compartment and to require
crew members to participate in approved firefighting
drills with the portable breathing equipment .2 3
REMOVAL OF TOXIC FUMES
. . . . ..
In at least two incidents involving onboard fires,
air-conditioning equipment was turned off, or engine
power cut, before or after landing, and that exacerbated
a serious situation with respect to toxic smoke. Smoke
and toxic fumes are the principal problem in noncrash
aircraft fires.
Industry practice, according to the results of the
Committee's review, is to specify using maximal outside-
air ventilation if smoke is present in the cabin or
cockpit and turning off recirculation systems if the
equipment includes this option. However, the details of
the emergency procedures are inconsistent, and in some
cases they cover only electric smoke or air-conditioning
smoke and are not explicit regarding cabin smoke.
All procedures that the Committee reviewed specified
increasing cabin altitude to 10,000 ft "to increase
ventilation." Although that will increase the volume of
air flowing through the cabin, the lower pressure will
also increase the volume of smoke produced by a given
fire, and there would be little or no reduction in smoke
concentration. Any reduction in burning rate due to the
decrease in partial pressure of oxygen in the cabin is
insignificant.
Deployment of oxygen masks in a fire is not
recommended by the airline procedures, because current
passenger oxygen masks only increase the oxygen
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concentrations in the air provided to passengers and do
not reduce the hazard of toxic fumes. The use of oxygen
masks could thus lead to an unwarranted sense of
security.
Details of the use of ventilation and pressurization
during an emergency descent due to a cabin fire were not
found in any of the procedures reviewed. In the Air
Canada incident near Cincinnati, in which air-
conditioning was turned off, air entering the cabin
during descent probably forced smoke into the cockpit.
During an unpressurized rapid descent, air enters the
cabin through the negative relief valves, which are
installed to prevent crushing of the fuselage. On the
DC-9, which was involved in the Air Canada incident, the
negative relief valves are above the ceiling in the aft
pressure bulkhead. Air entering through these valves
would have been forced over the fire and would have
carried smoke forward through the area above the ceiling
and caused it to enter the forward cabin and the cockpit.
As discussed in Appendix A, the steady-mate
concentration of fumes in an aircraft cabin is the
effective volume production rate, P. divided by the loss
frequency, L. L is found by dividing the outside-air
ventilation rate by the cabin volume. Both decreasing P
(by inhibiting ignition, extinguishing a fire, and
improving materials) and increasing L (by using the
maximal available outside-air ventilation rate) reduce
fume concentration. The Committee strongly recommends
that cabin-fire instructional material emphasize the
need to turn on all available air packs to full volume
if a cabin fire or smoke is present. That should reduce
the possibility of smoke in the cabin and increase the
likelihood of passenger survival. All recirculation
should be turned off if the equipment includes this
option.
FAA, manufacturers, and the airlines should conduct
further analyses aimed at developing detailed procedures
for optimal crew management of pressurization,
ventilation, auxiliary ventilation (if available), and
exhaust systems to control smoke during an emergency
descent. Because current supplemental oxygen masks are
designed to substitute cabin air for oxygen automatically
whenever the cabin pressure is below the equivalent
altitude of about 18,000 ft. even attaching the oxygen
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masks to a clean-air intake would not eliminate the
hazard of breathing smoke and toxic fumes. Detailed
procedures should also be developed for engine and air
pack shutdown and for use of an auxiliary power unit
after landing, to continue to provide ventilation and
prevent buildup of heat and flammable fumes that could
produce flashover during evacuation.
INDIVIDUAL SMOKE AND FUME PROTECTION
Because smoke and toxic fumes are principal causes
of death in survivable crashes, smoke hoods and other
passenger breathing devices have been proposed as a way
of protecting passengers and increasing the likelihood
of their survival. The studies referred to below
suggest that some protection could be gained through
their use, but there are limitations and difficulties.
After a crash in 196S, CAMI embarked on a program to
develop passenger smoke hoods.1 7 The program led to
announcement of an amendment to FAR Part 121 in 1969
that would have required protective smoke hoods to be
available on all civil air carrier.24 A number of
critical comments were received, mostly involving hood
safety, practicality, slowing of evacuation, and
Justification of the specifications. In response to
these comments9 and over the strong objection of the
medical and regulatory arms of FAA, the proposed rule
was withdrawn in September 1969.' 7
Several protective devices have been developed,
ranging from a simple moist multilayer cloth large
enough to cover the mouth and nose and held to the mouth
and nose by hand or by an elastic band around the head
(the North American Rockwell smoke mask) to hoods
incorporating compressed-air or oxygen generators (e.g.,
the experimental FAA-Sheldahl hood with self-contained
air supply, the Lear-Siegler air capsule, and the Scott
aviation emergency smoke hood and breathing device). In
addition, devices developed for other purposes, such as
escape from mines, have been examined for their
applicability as passenger protective devices. \7
It was widely publicized that cabin attendants
passed out wet towels during the Air Canada in-flight
fire aboard a DC-9. However, that was probably not
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effective--only a small percentage of the passengers who
were given wet towels survived.3
The relative advantages and disadvantages of
passenger smoke hoods and other protective breathing
devices have been assessed. In 1969, the Air Transport
Association appended to its comments on the proposed
rule the concerns of Richard L. Riley and Solbert
Permutt, of the Johns Hopkins University Department of
Environmental Medicine, about the hazard of hypoxia
created by the configuration of the smoke hood itself.
They were especially concerned about prolonged
breath-holding and were uncertain about whether all
passengers would remove their hoods when the carbon
dioxide in the hoods exceeded the generally accepted
safe concentration.
In 1970, FAA asked the National Research Council
Space Science Board to evaluate the smoke hood.13 The
Board pointed out several potential hazards, including
the narcotic effect of high concentrations of carbon
dioxide (9.2%), the impossibility of effecting
resuscitation once respiratory failure has been brought
about by inhalation of pure carbon dioxide, and the
possibility of hypoxia. It raised the legal question
regarding a lethally injured person who is found wearing
a smoke hood after a fire when cause of death is
difficult to determine. And it raised questions about
the use of the hood by people with cardiac disease or
pulmonary dysfunction and about the fitting of the device
for infants, children, and people with an abnormal neck
size.
In 1976, several smoke hoods were reviewed in a
report of the NATO Advisory Group for Aerospace Research
and Development.l 7 The report examined leakage,
effectiveness in toxic environments, vision, acoustic
attenuation, effectiveness in dense smoke environments,
and effectiveness of safety briefings. It concluded
that the available Sheldahl rebreathing smoke hood with
septal neck seal (Type S) "can provide protection from
smoke, toxic fumes, and flame in postcrash fire emergency
egress" and stated that "its demonstrated merits far
outweigh any potential risks or problems." That Judgment
appears to have considered all the problems noted above,
except the issues of legal responsibility and liability.
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The Ontario Research Foundation, in Canada, recently
completed an evaluation of over 20 devices and extensive
tenting of six, all of which include filtration or
absorption. 6 Test criteria included edge leakage,
smoke and toxic gas penetration of filtration units,
condition of inhaled air (carbon dioxide, oxygen, and
temperature), comforts ease of donning, breathing
resistance
resistance
_ ~ ~ ~. ~.
of filtration units, vision and communication,
to flame, cost, size and weight, and
compactly warn current passenger supplemental oxygen
systems. The report concluded that a compact device
providing both Repressurization and protection from toxic
smoke and gas for airline passengers in feasible and
that the devices tested can provide several extra minutes
of escape time. However, although the study considered
use of the devices under several different conditions
(sitting, walking, talking, and light exercise), it did
not evaluate their use under conditions corresponding to
the evacuation of an aircraft during a fire.
The FAA position is that efforts to reduce the
likelihood of ignition or smoldering fire have diminished
the need for individual passenger smoke and fume
protection dulcet. FAA bases its position on the
relative merits of four basic types of passenger
emergency breathing devices: simple smoke hoods with
neck seal and no oxygen supply, hoods or masks that
connect to the individual ventilation outlets (gaspers),
modifications of current oxygen masks, and hoods or
masks with individual self-contained oxygen supplies.
· FAA concluded that simple smoke hoods are of
limited utility, because of the restrictions on the
length of time they can be worn before effects of
hypoxia, carbon dioxide poisoning, etc., set in. The
time involved in a typical incident associated with an
in-flight fire at cruise altitude--including emergency
descent, landing at the (possibly unscheduled) airport,
stopping, and evacuation--is sufficient to make adverse
behavioral and physiologic effects likely. In one study
in which smoke hoods were donned in a darkened cabin and
the aircraft was evacuated, the use of smoke hoods
reportedly increased evacuation times by 50%
(T. E. McSweeny, personal communication, 1986~.
· It all aircraft have Raspers, and they are not
commonly selected by airlines for current aircraft
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models. Thus, the connection of hoods or masks to
gaspers cannot be considered a general solution. More
important, most ventilation systems on current aircraft
involve at leant some recirculation of air in the cabin.
Connection of hoods or masks to gaspers thus presents
the possibility of introducing smoke or toxic fumes
directly into the passengers' air supply.
· F. M considers modification of current
supplemental oxygen masks to be the most promising of
the options examined. However 9 the current diluter
demand mask operates as a function of cabin altitude.
Below a cabin altitude of about 20,000 ft. no oxygen is
introduced, and the system relies on air from the
standard ventilation system, so it is also subject to
possible contamination with smoke and fumes, as are
gaspers. Modification of the oxygen supply system to
cover the time required for descent, landing, stopping,
and evacuation would require re-engineering of the
oxygen supply systems and considerable extension of the
oxygen supply. Careful thought must be given to the
addition of large amounts of oxygen in an extensive
network of overhead tubes, because it would be in the
same portion of the cabin that is typically subjected to
the greatest temperatures and to flashover conditions.
· FAA has given less attention to self-contained
breathing devices, mostly because of their greater
cost. Furthermore, passengers have found it difficult
to don and use current oxygen masks and life vests
properly and would probably have even more trouble with
more complicated breathing devices.
For these reasons, FAA hen chosen to pursue
engineering solutions involving selection of materials,
fire detection and extinguishing, evacuation and
development of a method of purging the aircraft of smoke
and toxic fumes in flight, rather than passenger
protective breathing device.
The FAA policy, however, is based on the premises
that flashover is not survivable and that the primary
concern in pontcrash fires or in-flight fires once the
aircraft has landed and stopped is rapid evacuation.
Although this initially appears valid, some people have
survived flashover. For example, two passengers and an
attendant hid in the aft stairwell of a B-737 involved
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in a large postcrash fire in 1965 until rescued 25 min
later. \6 They survived, one on top of the other, by
breathing through a small crack in the fuselage. The
one on top, a 61-yr-old man, died of burn injuries on
the seventh postcrash day. In the recent British
Airtours accident in Manchester, England, a B-737 caught
fire and burned. A 14-yr-old boy was removed from the
aircraft approximately S min after flashover and
survived. An older man was rescued from the same
aircraft 30 min after flashover and survived for 6 d
before succumbing (E. J. Trimbell, personal
communication, 1986~. On the basin of that incident,
the Accident Investigation Branch of the U.K. Department
of Transport has strongly recommended that the Civil
Aviation Authority require passenger breathing devices
in that country.
The Committee feels that passenger smoke hoods and
breathing devices should be evaluated in terms of their
potential contribution to survival and their effect on
such factors as evacuation time. In case toxic fumes
are the reason for a need for quick escape, protection
at the slight expense of speed might save many lives.
This needs to be critically examined.
Despite the incompleteness of data on the
effectiveness of passenger protective breathing devices
under realistic conditions, the Committee recommends
that such systems be studied. Published reports suggest
that one passenger could be saved for each second added
to the time available for escape in an emergency
evacuation of an aircraft on which a fire is generating
toxic smoke.7 It might be worth while to reinvestigate
this life-sustaining protective breathing equipment in
light of recent developments in contaminant absorption
and self-contained sources of air or oxygen for such
units.
EMERGENCY ESCAPE
On October 269 1984, FAA published a new requirement
for floor-proximity emergency escape-path marking that
provides visual guidance for emergency escape when all
sources of cabin lighting more than 4 ft above the floor
are totally obscured. 2 ~ Although this standard does
not affect cabin air quality, it is designed to deal
with a situation of severely degenerated air quality.
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PASSENGER SAFETY BRIEFINGS
In-flight or postcrash fires are never mentioned by
cabin crew in their passenger safety instructions.
Toxic, noxious, and blinding gaseous products and
particulate matter resulting from fire stratify in the
aircraft in such a way that the best air is closest to
the floor, but this potentially vital information is not
given to passengers. However, when speed is critical for
evacuation, staying close to the floor under conditions
of limited visibility might be counterproductive.
DEPRESSURIZATION
The primary threat to the passenger in
depressurization is hypoxia. The main problem is in
inducing passengers to don their oxygen masks correctly
and quickly.
Records in the CAMI Cabin Safety Data Bank show a
total of 355 incidents involving Repressurization in
1974-1983 (Table 4-2~. Of these, 43% were classified as
"significant" incidents--i.e., cabin pressure decreased
to an equivalent altitude above 14,000 ft. passenger
masks were deployed, or an injury resulted.8 Only
one death occurred: that of a passenger with a history
of heart problems. There were three serious injuries:
one cockpit crew member had a broken arm, one passenger
had a nonfatal heart attack, and one passenger had a
collapsed lung. Sixty-six passengers and two cockpit
crew members reported minor ear pain; 55 passengers and
two cockpit crew members reported intense ear pain; 11
passengers incurred serious ear damage, including eight
with bleeding ears; and three passengers suffered
nosebleeds. No flight attendants reported any of these
problems.
Seventeen cases of hypoxia were reported: seven
passengers and five flight attendants suffered mild
hypoxia, and one passenger and four flight attendants
suffered loss of consciousness. No cockpit crew members
reported symptoms of hypoxia, perhaps because they are
usually the first to be aware that Repressurization has
occurred and have ready access to masks with demand
regulators.
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107
TABLE 4-2
Ten-Year History of Reported Depressurizations,
1974-1983a
No. No. No. Total
Significantb Minor Undefined No.
Year IncidentsIncidents Incidents Incidents
197418 24 12 54
197515 22 1 38
197617 10 6 33
197716 13 2 31
197816 17 6 39
197920 18 7 45
198019 20 5 44
198118 12 4 34
19828 8 2 18
19837 6 6 19
Total154 150 51 355
a Data from Higgins.8
b See text for definition of "significant."
In studies conducted at CAMI in 1976, it was
determined that the physical activity typical of a
flight attendants duties reduces the time of useful
consciousness (amount of time until mental functioning
deteriorates) by about 40% compared with that of an
inactive passenger.
If rapid d enrenn''r! 7= ~ ~ ^- ^~-
~ _% ~ _ _ ~ ~
"~` "~cenuanc nas only 15-20 a, depending on altitude and
final cabin pressure, to don a mask before adverse
effects, such as mental sluggishness, begin.
The continuous-flow passenger mask has
Q 9 t" ~ ~ ¢^ ~_.. =~ ~ ~ _ ~ . · . ~
~ ~ -~v ~ ~ our canon a'c~tuces up to 40,000 ft. when
properly used.
Most of the problems with this type of
mask appear to be associated with the lack of timely or
proper donning--for example, failure to pull the mask
down to activate the oxygen flow, failure to ensure that
the mask covers both nose and mouth, and failure to
tighten the straps to ensure a good fit.8
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108
The problem of depressurization thus has to do
essentially with passenger retention of safety
instructions and quickness of response. Issues
involving cabin safety procedures and information
presentation are dealt with in Chapter 3.
CONCLUSIONS AND RECOMMENDATIONS
The Committee concludes that, although the ignition
and propagation of fires and the resulting generation of
combustion products aboard commercial airliners is
complex, much can be accomplished toward alleviating the
associated hazards. The use of materials that have high
resistance to burning, that will not propagate a flame,
and that will not generate toxic products when subjected
to heat loads sufficient to cause currently used
materials to degenerate would constitute a distinct
improvement in passenger safety and air quality in the
event of an in-flight, postcrash, or landing fire. The
Committee recommends that FAA review current airline
operating procedures and flight crew instructions for
emergencies involving cabin fire or smoke; this review
should cover every type of aircraft, regardless of size,
in commercial service in the United States. The
Committee recommends that the Aerospace Industries
Association of America, a similarly constituted
organization of airframe manufacturers, or even an
individual manufacturer be encouraged to fund and
initiate a program to develop a more fire-resistant set
of materials from which to fabricate fully functional
interior materials for aircraft.
The Committee concludes that smoke hoods or other
protective breathing and vision devices would provide
additional passenger survival time in an otherwise
debilitating situation that might normally preclude
survival. FAA should re-evaluate smoke hoods or special
breathing devices for passenger use.
The Committee recommends immediate implementation of
directions to turn on all air packs and to turn off
internal recirculation systems in case of onboard fire.
The Committee recommends that air contamination modeling
studies and confirmatory live testing in aircraft be
performed as soon as possible, by properly constituted
FAA-industry teams, to determine conclusively the
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109
advantages of turning on all packs to full volume when
there is an in-flight fire.
The Committee recommends that FAA require
information on proper response to fire emergencies to be
included in oral and written passenger safety briefings.
REFERENCES
1. Aerospace Industries Association of America, Inc.
Comments to NPRM 85-lOa, "Improved Flammability
Standards for Materials Used in the Interiors of
Transport Category Airplane Cabins," Docket No.
24594. (unpublished communication, October 16,
1985)
2. Aerospace Industries Annociation of America, Inc.
Final AIA comments to NPRM 85-1OA, "Improved
Flammability Standards for Materials Used in the
Interiors of Transport Category Airplane Cabins,"
Docket No. 24594. (unpublished communication,
January 8 9 1986)
Barthelmess, S. Flight 797: A h~man-factors
perspective. Part II. FSF Flight Safe. Dig.
(Aug.~:12-17, 1984.
4. Bulloch, C. Survivability in aircraft fires: New
standards are needed. Interavia 34:557-558, 1979
5. Compartment interiors. Code of Federal
Regulations, Title 14, Pt. 25.853. Washington,
D.C.: U.S. Government Printing Office, 1985.
6. Dranitsaris, P. An Evaluation of Candidate Smoke
Masks for Passenger Use in Airplane Fires. Draft
Report P-4612/G. Mississauga, Ontario: Ontario
Research Foundation, 1986.
Hall, J. R., and S. W. Stiefel. Decision Analysis
Model for Passenger Aircraft Fire Safety with
Application to Fire-Blocking of Seats: Interim
Report' November 1982-December 1983. NBSIR
84-2817, DOT/FAA/CT-84/8. Atlantic City, N.J.
U.S. Federal Aviation Administration Technical
Center, 1984.
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110
8. Higgins, E. A. Protective breathing: Oxygen mask
use/problems, pp. 61-65. In Flight Safety
Foundation, Inc. Proceedings of Cabin Safety
Conference and Workshop, December 11-14, 1984.
Washington, D.C.: U.S. Federal Aviation
Administration, Office of Aviation Safety, 1985.
9. Hill, R. G., T. I. Eklund, and C. P. Sarkos.
Aircraft Interior Panel Test Criteria Derived from
Full-Scale Fire Tests. DOB/FAA/CT-85/23.
Atlantic City, N.J.: U.S. Federal Aviation
Administration, Technical Center, 1985.
10. Johnston, W. L., and P. T. Cahalane. Examination
of fire safety of commercial aircraft cabins.
SAFE J. 15(2):4-9, 1985.
11. McSweeny, T. E. FAA cabin safety activities, pp.
30-44. In Flight Safety Foundation, Inc.
Proceedings of Cabin Safety Conference and
Workshop, December 11-14, 1984. Washington, D.C.:
U.S. Federal Aviation Administration, Office of
Aviation Safety, 1985.
12. Miniazewski, K. R., T. E. Waterman, J. A.
Campbell, and F. Salzberg. Fire
Management/Suppression Systems/Concepts Relating
to Aircraft Cabin Fire Safety: Final Report.
DOT/FAA/CT-82/134. Atlantic City, NeJ. UeS.
Federal Aviation Administration Technical Center,
1983.
13. National Research Council, Space Science Board.
Evaluation of Smoke Hoods. 1970. (unpublished
document)
14. Sarkos, C. P. New FAA regulations improve
aircraft fire safety. ASTM Standardization News
13~12~:33-39, 1985.
15. Sarkos, C. P., R. G. Hill, and W. D. Howell.
Full-scale wide-body test article employed to
study post crash fuel fires. ICAO Bull.
37~10~:30-39, 1982.
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111
Snow, C. C., J. J. Carroll, and M. A. Allgood.
Survival in Emergency Escape from Passenger
Aircraft. AM 70-16. Washington, D.C.: U.S.
Federal Aviation Administration, Office of
Aviation Medicine, 1970. (available from NTIS as
AD-735388)
17. Snyder, R. G. Advanced Techniques in Crash Impact
Protection and Emergency Egress from Air Transport
Aircraft. AGARD-AG-221. London: North Atlantic
Treaty Organization, Advisory Group for Aerospace
Research and Development, 1976. (available from
NTIS as AD-A029375)
18. U.S. Federal Aviation Administration. Airplane
cabin fire protection: Final rule. Federal
Register 50~29 March):12726-12733, 1985.
U.S. Federal Aviation Administration. Fire
protection requirements for cargo or baggage
compartments: Notice of proposed rulemaking.
Federal Register 49~8 Aug.~:31830-31838, 1984.
20. U.S. Federal Aviation Administration.
Flammability requirements for aircraft seat
cushions: Final rule. Federal Register 49~26
Oct.~:43188-43200, 1984.
21. U.S. Federal Aviation Administration. Floor
proximity emergency escape path marking: Final
rule. Federal Register 49~26 Oct.~:43182-43186,
1984.
22. U.S. Federal Aviation Administration. Improved
flammability standards for materials used in the
interior of transport category airplane cabins:
Notice of proposed rulemaking. NPRM 85-10.
Federal Register 50~16 April):15038-15053, 1985.
23. U.S. Federal Aviation Administration. Protective
breathing equipment: Notice of proposed rule-
making. Federal Register 50~10 Oct.~:41452-41459,
1985.
24. U.S. Federal Aviation Administration. Protective
smoke hoods for emergency use by passengers and
crewmembers: Notice of proposed rule making.
Federal Register 34~11 Jan.~:465-466, 1969.
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25. U.S. Federal Aviat10n Administration' Special
Aviation Fire and E~p10810~ Redaction (SAFER)
Advisory Committee. Fina1 Report. Vol. 1.
FAA-ASF-80-4. Washington, D.C.: U.S. Federa1
Aviation Administrations 1980. (available from
NTIS as AD-A092016)
Representative terms from entire chapter:
toxic fumes
