[Federal Register Volume 59, Number 83 (Monday, May 2, 1994)]
[Unknown Section]
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From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 94-9759]
[[Page Unknown]]
[Federal Register: May 2, 1994]
_______________________________________________________________________
Part II
Department of Transportation
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Federal Aviation Administration
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14 CFR Part 25
Allowable Carbon Dioxide Concentration in Transport Category Airplane
Cabins; Proposed Rule
DEPARTMENT OF TRANSPORTATION
Federal Aviation Administration
14 CFR Part 25
[Docket No. 27704; Notice No. 94-14]
RIN 2120-AD47
Allowable Carbon Dioxide Concentration in Transport Category
Airplane Cabins
AGENCY: Federal Aviation Administration, DOT.
ACTION: Notice of proposed rulemaking.
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SUMMARY: This notice proposes to revise the standards for maximum
allowable carbon dioxide (CO2) concentration by reducing the
allowable maximum concentration from 3 percent to 0.5 percent in
occupied areas of transport category airplanes. This action is in
response to a recommendation from the National Academy of Sciences to
review the CO2 limit in airplane cabins, and would provide a cabin
CO2 concentration equivalent to that recommended for buildings.
DATES: Comments must be received on or before August 30, 1994.
ADDRESSES: Send comments on this notice in triplicate to: Federal
Aviation Administration, Office of the Chief Counsel, Attn: Rules
Docket (AGC-200), Docket No. 27704, 800 Independence Avenue SW.,
Washington, DC 20591; or deliver comments in triplicate to: Federal
Aviation Administration, room 915G, 800 Independence Avenue SW.,
Washington, DC 20591. Comments must be marked Docket No. 27704.
Comments may be examined in the Rules Docket weekdays, except Federal
holidays, between 8:30 a.m. and 5 p.m. In addition, the FAA is
maintaining an information docket of comments in the Office of the
Assistant Chief Counsel (ANM-7), Federal Aviation Administration,
Northwest Mountain Region, 1601 Lind Avenue SW., Renton, Washington
98055-4056. Comments in the information docket may be examined in the
Office of the Assistant Chief Counsel weekdays, except Federal
holidays, between 7:30 a.m. and 4 p.m.
FOR FURTHER INFORMATION CONTACT:
Bob McCracken, FAA, Flight Test and Systems Branch, ANM-111, Transport
Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue
SW., Renton, Washington 98055-4056; telephone (206) 227-2118.
SUPPLEMENTARY INFORMATION:
Comments Invited
Interested persons are invited to participate in this proposed
rulemaking by submitting such written data, views, or arguments as they
may desire. Comments relating to any environmental, energy, federalism,
or economic impacts that might result from adoption of the proposal
contained in this notice are also invited. Substantive comments should
be accompanied by cost estimates. Commenters should identify the
regulatory docket or notice number and submit comments in triplicate to
the Rules Docket address above. All comments received on or before the
closing date for comments will be considered by the Administrator
before taking action on this proposed rulemaking. The proposal
contained in this notice may be changed in light of comments received.
All comments received will be available in the Rules Docket, both
before and after the closing date for comments, for examination by
interested persons. A report summarizing each substantive public
contact with FAA personnel concerning this rulemaking will be filed in
the docket. Persons wishing the FAA to acknowledge receipt of their
comments must submit with those comments a self-addressed, stamped
postcard on which the following statement is made: ``Comments to Docket
No. 27704.'' The postcard will be date stamped and returned to the
commenter.
Availability of NPRM
Any person may obtain a copy of this Notice of Proposed Rulemaking
(NPRM) by submitting a request to the Federal Aviation Administration,
Office of Public Affairs, Attention: Public Inquiry Center, APA-230,
800 Independence Avenue SW., Washington, DC 20591; or by calling (202)
267-3484. Communications must identify the notice number of this NPRM.
Persons interested in being placed on the mailing list for future NPRMs
should also request a copy of Advisory Circular No. 11-2A, Notice of
Proposed Rulemaking Distribution System, which describes the
application procedure.
Background
In October 1984, the Department of Transportation was directed by
Congress (Pub. L. 98-466) to commission the National Academy of
Sciences (NAS) to conduct an independent study on the cabin air quality
in transport category airplanes. The NAS formed the Committee on
Airliner Cabin Air Quality to study all safety aspects of airliner
cabin air quality, and submitted its report, ``The Airliner Cabin
Environment--Air Quality And Safety,'' to the FAA on August 12, 1986.
The report includes 19 recommendations for legislative, regulatory, and
air transport industry changes in relation to airliner cabin air
quality. One of the recommendations relates to the allowable carbon
dioxide (CO2) concentration in the airplane cabin. This action is
a result of that recommendation. For the purposes of this notice, the
term, ``cabin'' is meant to include the passenger cabin, the flight
deck, lower lobe galleys, crew rest areas, and any other occupied areas
in a transport category airplane.
Discussion
Carbon dioxide is the product of normal human metabolism, which is
the predominant source in aircraft cabins. The CO2 concentration
in the cabin depends on the ventilation rate, the number of people
present, and their individual rates of CO2 production, which
varies with activity and (to a smaller degree) with diet and health.
The carbon dioxide concentration level is frequently used as an
indication of general air quality. At concentrations above a given
level, complaints of poor air quality or ``stuffiness'' begin to
appear.
The current maximum CO2 limit of Sec. 25.831(b)(2) of the
Federal Aviation Regulations (FAR) is 3 percent by volume, sea level
equivalent. This 3 percent limit was incorporated into Sec. 4b.371 of
the Civil Air Regulations (CAR) by Amendment 4b-6 on March 5, 1952.
This limit was carried over into 14 CFR part 25 of the FAR when this
part was codified in 1965. This high limit was established to allow for
increases in the carbon dioxide levels in the crew compartment to
ensure that, in aircraft with built-in carbon dioxide fire
extinguishing systems, safe carbon dioxide concentrations would not be
exceeded in the crew compartment when combating fires in cargo
compartments.
The American Conference of Governmental Industrial Hygienists
(ACGIH) has adopted a short-term exposure limit (STEL) for CO2 of
30,000 parts per million (3 percent). The 3 percent limit specified in
part 25 may therefore be satisfactory as a short-term limit, but is
inappropriate for a steady-state condition. However, the NAS Committee
notes in their report that this 3 percent limit is much higher than the
limits adopted by the air conditioning industry for buildings and other
types of interior environments, and recommends that the limit specified
in part 25 be revised to more closely match the currently acceptable
limits. The FAA concurs.
In contrast to the 3 percent limit specified in part 25, Standard
62-1989, prepared by the American Society of Heating, Refrigerating,
and Air-Conditioning Engineers (ASHRAE), recommends a CO2 limit of
1,000 parts per million (PPM), or 0.1 percent. As CO2
concentration in the air increases, there is an increase in both the
rate and the depth of breathing, reaching twice the normal rate at 3
percent concentration. At 3 percent concentration, there is some
discomfort; at higher concentrations, headache, malaise, and fatigue
occur, and the air is reported by those affected as being stale. People
can function for long periods of time at levels of CO2 as high as
1 percent (as in nuclear submarines), but it is generally felt by
ASHRAE that 0.1 percent is a better limit. This value, however, is
based on the dissipation of smoke and odors and not on health
considerations. According to the ASHRAE Standard 62-1989, a steady-
state CO2 concentration of 0.1 percent would require a fresh-air
ventilation rate of 15 cubic feet per minute (cfm) per person. In the
old standard (62-1981), ASHRAE recommended a limit of 0.5 percent for
office buildings and other occupied spaces, but suggested that 0.25
percent would provide an additional safety factor.
The Occupational Safety and Health Administration (OSHA), in 29 CFR
1910.1000, sets an interim (transitional) limit for CO2 at 5,000
ppm or 0.5 percent, with a final rule limit of 10,000 ppm or 1 percent,
which becomes effective December 31, 1993. The increase to 1 percent is
apparently in deference to operators of commercial bakeries and
breweries, both of which generate a significant amount of CO2 in
their processes. The FAA does not believe it is appropriate to base the
allowable CO2 concentration in transport category airplanes on the
needs of specific manufacturing processes. Other commercial enterprises
have no difficulty in meeting the existing OSHA limit of 0.5 percent.
The American Conference of Governmental Industrial Hygienists, in
its ``Documentation of the Threshold Limit Values and Biological
Exposure Indices--Sixth Edition,'' also recommends 0.5 percent as the
time weighted average limit for repeated daily exposure by workers. The
FAA proposes adopting this value as a limit. A concentration limit of
0.5 percent is considered to be appropriate because there are no
documented safety or health benefits associated with a lower value.
Parties reviewing this document are encouraged to comment on values
between 0.1 percent and the existing 3 percent limit, and to provide
justification for any recommendations. The FAA may determine, based on
the comments, that a limit different from 0.5 percent is appropriate
and change the final rule accordingly.
Copies of the pertinent documents from ASHRAE, OSHA, and ACGIH have
been placed in the public docket for this proposed rulemaking.
Cabin ventilation provides air for dilution of airborne
contaminants, and supplies oxygen for passengers and crew. Oxygen
requirements for sedentary adults can be met with a fresh-air
ventilation rate of only 0.24 cubic feet per minute (CFM) per person.
This low ventilation rate is also sufficient to dissipate the water
vapor produced by cabin occupants. Ventilation rates for current
transport category airplanes vary from a low of approximately 7 cfm per
person (with one or more air conditioning packs turned off for
economy), to over 20 cfm per person (which includes up to 50 percent
filtered, recirculated air). Thus, even at the lowest ventilation rates
available on current aircraft, there is no significant reduction in the
percentage of oxygen, or increase in the amount of water vapor in the
cabin due to respiration. Ventilation for the control of CO2
buildup due to respiration is therefore the factor that dictates design
parameters for ventilation systems, although many airplane systems are
sized much larger than the minimum required for passenger comfort.
Contamination of air with CO2 varies inversely with the
ventilation rate, because CO2 production by sedentary people is
nearly constant.
In order to bring the maximum allowable carbon dioxide
concentration into concert with accepted modern limits, this NPRM
proposes to reduce the maximum allowable carbon dioxide concentration
from the current value of 3 percent to 0.5 percent. According to
ASHRAE, for sedentary people, this concentration can be maintained by a
fresh air flow rate of 2.25 cfm, which is lower than that currently
measured in transport category aircraft.
Section 25.831(b)(2) currently states that ``Carbon dioxide in
excess of three percent * * * is considered hazardous in the case of
crewmembers.'' The health and comfort considerations discussed earlier
are equally valid for passengers. Therefore, the FAA proposes to remove
the reference to crewmembers. In addition, Sec. 25.831(b)(2) currently
contains the following sentence: ``Higher concentrations of carbon
dioxide may be allowed in crew compartments if appropriate protective
breathing equipment is available.'' This sentence was incorporated when
the 3 percent limit was established in CAR 4b.371 in 1952. As noted
above, the origins of the 3 percent limit are unclear, but it is likely
that the limit was set at this high level to account for the discharge
of CO2 fire extinguishers in the flight deck or cabin. This thesis
is supported by the mention of protective breathing in the existing
rule. However, most CO2 extinguishers have been replaced by Halon
or other types of fire extinguishers. Further, the rule is not intended
to cover the short-duration rise in CO2 concentration that would
accompany discharge of a fire extinguisher. Removal of the sentence
from Sec. 25.831(b)(2) is proposed because it is no longer considered
necessary or appropriate.
Section 25.831 also specifies a limit for carbon monoxide (CO)
concentration of 1 part in 20,000 parts air (0.005 percent). This limit
is the same as currently recommended by ASHRAE and the Occupational
Safety and Health Administration (OSHA), and therefore this notice does
not propose to change this limit.
Regulatory Evaluation
This section summarizes the full regulatory evaluation that
provides more detailed estimates of the economic consequences of this
regulatory action. This summary and the full evaluation quantify, to
the extent practicable, estimated costs and anticipated benefits to the
private sector, consumers, and Federal, State and local governments.
Proposed changes to Federal regulations must undergo several
economic analyses. First, Executive Order 12866 directs that each
Federal agency shall propose or adopt a regulation only upon a reasoned
determination that the benefits of the intended regulation justify its
costs. Second, the Regulatory Flexibility Act of 1980 requires agencies
to analyze the economic impact of regulatory changes on small entities.
Finally, the Office of Management and Budget directs agencies to assess
the effects of regulatory changes on international trade. In conducting
these analyses, the FAA has determined that this proposed rule: (1)
Would generate benefits that would justify its costs and is not a
``significant regulatory action'' as defined in the Executive Order;
(2) is not significant as defined in Department of Transportation
Regulatory Policies and Procedures; (3) would not have a significant
impact on a substantial number of small entities; and (4) would not
have a negative impact on international trade. These analyses,
available in the docket, are summarized below.
Costs
Carbon dioxide (CO2) is a byproduct of human metabolism and is
expelled through respiration. The proposed rule would reduce the
maximum allowable CO2 concentration, as specified in
Sec. 25.831(b)(2), from 3 percent to 0.5 percent in occupied areas of
transport category airplanes.
In a confined space, the production of CO2 is a function of
the number of people present, their activity levels, and, to a lesser
extent, their diet and health. The concentration of CO2 in an
aircraft is controlled by ventilation of the cabin through the
introduction of outside air through the aircraft's environmental
control system. For a given set of production and ventilation
conditions, the resulting CO2 concentration can be calculated
reliably. In addition, engineering analyses have been conducted to
determine the fuel that is consumed in providing a unit rate of
ventilation.
Taken together, these functional relationships make it possible to
calculate the costs necessary to maintain CO2 concentrations at a
given level under established conditions. It is estimated that the
current 3 percent CO2 concentration limit can be maintained at a
cost of .3 cents per passenger-hour. The lower proposed 0.5 percent
limit would cost approximately 2.1 cents per passenger-hour, and would
constitute an increase of 1.8 cents per passenger-hour. It should be
noted that these are ``zero baseline'' estimates, and do not take into
account the cost associated with the fresh air already introduced into
the airplane for pressurization and other purposes. In actuality,
existing and probable new airplanes currently have and will in the
future be designed to have fresh air inflow rates that provide air with
a CO2 concentration well below the proposed 0.5 percent. For this
reason, there are no actual costs associated with this proposal.
Benefits
CO2 is naturally present at low concentration (.03 percent) in
outdoor air. When CO2 is inhaled in progressively elevated
concentrations, it may act to produce stimulation of the respiratory
center, mild narcotic effects, and asphyxiation, depending on the
concentration and the duration of exposure. Numerous studies have been
conducted to determine the effects of exposure to elevated CO2
concentrations. At concentrations of 2 to 3 percent, CO2 produces
effects such as headaches, breathing difficulty, and increases in blood
pressure and pulse. By comparison, no symptoms are induced at the
proposed 0.5 percent level.
Cost-Benefit Comparison
A strict cost-benefit evaluation of the proposed rule change
itself, without consideration of the fact that operators currently
comply with the proposed standard, concludes that the cost of the
increased ventilation necessary to reduce CO2 concentration from 3
percent to 0.5 percent would be 1.8 cents per passenger-hour. The
proposed reduction would prohibit CO2 concentration levels known
to produce effects such as headaches, breathing difficulty, and
increases in blood pressure and pulse. While no precise economic value
has been assigned to this benefit, the FAA believes that it would be
worth more than 1.8 cents per hour per passenger to avoid such ill
effects.
The evaluation described above looks solely at the proposed change
in the rule. In fact, the minimum ventilation in current transport
category aircraft maintains CO2 concentrations below the proposed
0.5 percent concentration. Accordingly, it is estimated that no direct
incremental costs or benefits would result from this proposed rule. The
rule would, however, preclude future certificated airplane models from
being designed to operate at CO2 concentrations above the 0.5
percent level. Because this dictates a minimum design requirement for
CO2 concentration in new airplane types, and any airplane must be
operated in accordance with its type design, this minimum concentration
would be maintained in actual operation unless a system failure occurs.
In addition, an intangible benefit would accrue from the fact that the
proposal would make the CO2 concentration limit for aircraft
consistent with the standards of other agencies and advisory
authorities.
Regulatory Flexibility Determination
The FAA has determined that under the criteria of the Regulatory
Flexibility Act (RFA) of 1980, the proposed amendment to part 25
contained in the notice would not have a significant economic effect on
a substantial number of small entities. The RFA requires agencies to
review rules which may have a ``significant economic impact on a
substantial number of small entities.'' The FAA has adopted criteria
and guidelines for determining whether a proposed or existing rule has
a significant economic effect on a substantial number of small
entities. Since no actual incremental costs are expected to be incurred
to comply with the requirements of the proposal, it would not have a
significant economic impact.
Trade Impact Statement
Since the certification rules apply to both foreign and domestic
manufacturers that sell aircraft in the United States, there would be
no competitive advantage to either. Since no actual costs are expected
to be imposed by this rule, it would not result in a competitive trade
disadvantage for U.S. manufacturers in foreign markets or for foreign
manufacturers in the United States.
Federalism Implications
The regulations proposed herein would not have substantial direct
effects on the States, on the relationship between the national
government and the States, or on the distribution of power and
responsibilities among the various levels of government. Therefore, in
accordance with Executive Order 12612, it is determined that this
proposal would not have sufficient federalism implications to warrant
the preparation of a Federalism Assessment.
Conclusion
Because the proposed revised standards for maximum allowable carbon
dioxide concentration are not expected to result in a substantial
economic cost or have a significant adverse effect on competition, the
FAA has determined that this proposed regulation is not significant
under Executive Order 12866. In addition, the FAA has determined that
this action is not significant as defined in Department of
Transportation Regulatory Policies and Procedures (44 FR 11034,
February 26, 1979). Since no actual incremental costs are expected to
be incurred to comply with the requirements of this proposal, the FAA
certifies, under the criteria of the Regulatory Flexibility Act, that
this proposed regulation, if adopted, will not have a significant
economic impact, positive or negative, on a substantial number of small
entities. A copy of the initial regulatory evaluation prepared for this
proposal may be examined in the public docket or obtained from the
person identified under the caption, FOR FURTHER INFORMATION CONTACT.
List of Subjects in 14 CFR Part 25
Aircraft, Aviation safety, Reporting and recordkeeping
requirements.
The Proposed Amendment
Accordingly, the Federal Aviation Administration (FAA) proposes to
amend 14 CFR part 25 of the Federal Aviation Regulations (FAR) as
follows:
PART 25--AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES
1. The authority citation for part 25 continues to read as follows:
Authority: 49 U.S.C. app. 1344, 1354(a), 1355, 1421, 1423, 1424,
1425, 1428, 1429, 1430; 49 U.S.C. 106(g); and 49 CFR 1.47(a).
2. Section 25.831(b)(2) is revised to read as follows:
Sec. 25.831 Ventilation.
* * * * *
(b) * * *
(2) Carbon dioxide in excess of 0.5 percent by volume (sea level
equivalent) is considered hazardous.
* * * * *
Issued in Washington, DC, on April 11, 1994.
Thomas E. McSweeny,
Director, Aircraft Certification Service.
[FR Doc. 94-9759 Filed 4-29-94; 8:45 am]
BILLING CODE 4910-13-M