# Hazardous Materials Regulations: Transportation of Compressed Oxygen, Other Oxidizing Gases and Chemical Oxygen Generators on Aircraft

- **operation:** document
- **citation:** 72 FR 4442
- **title:** Hazardous Materials Regulations: Transportation of Compressed Oxygen, Other Oxidizing Gases and Chemical Oxygen Generators on Aircraft
- **source type:** rulemaking
- **agency:** Pipeline and Hazardous Materials Safety Administration
- **status:** historical
- **official:** true
- **published on:** 2007-01-31
- **effective on:** 2007-10-01
- **summary:** PHMSA (also, "we" or "us") is amending the Hazardous Materials Regulations (HMR) to: require cylinders of compressed oxygen and other oxidizing gases and packages of chemical oxygen generators to be placed in an outer packaging that meets certain flame penetration and thermal resistance requirements when transported aboard an aircraft; revise the pressure relief device (PRD) setting limit on cylinders of compressed oxygen and other oxidizing gases transported aboard aircraft; limit the types of cylinders authorized for transporting compressed oxygen aboard aircraft; and convert most of the provisions of an oxygen generator approval into requirements in the HMR. PHMSA is issuing this final rule in cooperation with the Federal Aviation Administration (FAA) to increase the level of safety associated with transportation of these materials aboard aircraft.
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- **source url:** https://www.federalregister.gov/documents/2007/01/31/E7-1487/hazardous-materials-regulations-transportation-of-compressed-oxygen-other-oxidizing-gases-and
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Federal Register, Volume 72 Issue 20 (Wednesday, January 31, 2007) [Federal Register Volume 72, Number 20 (Wednesday, January 31, 2007)] [Rules and Regulations] [Pages 4442-4458] From the Federal Register Online via the Government Publishing Office [ www.gpo.gov ] [FR Doc No: E7-1487] ======================================================================= ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION Pipeline and Hazardous Materials Safety Administration 49 CFR Parts 171, 172, 173, 175 and 178 [Docket No. RSPA-04-17664 (HM-224B)] RIN 2137-AD33 Hazardous Materials Regulations: Transportation of Compressed Oxygen, Other Oxidizing Gases and Chemical Oxygen Generators on Aircraft AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA), DOT. ACTION: Final rule. ----------------------------------------------------------------------- SUMMARY: PHMSA (also, ``we'' or ``us'') is amending the Hazardous Materials Regulations (HMR) to: require cylinders of compressed oxygen and other oxidizing gases and packages of chemical oxygen generators to be placed in an outer packaging that meets certain flame penetration and thermal resistance requirements when transported aboard an aircraft; revise the pressure relief device (PRD) setting limit on cylinders of compressed oxygen and other oxidizing gases transported aboard aircraft; limit the types of cylinders authorized for transporting compressed oxygen aboard aircraft; and convert most of the provisions of an oxygen generator approval into requirements in the HMR. PHMSA is issuing this final rule in cooperation with the Federal Aviation Administration (FAA) to increase the level of safety associated with transportation of these materials aboard aircraft. DATES: Effective Date: The effective date of these amendments is October 1, 2007. Voluntary Compliance: Voluntary compliance with all these amendments, including those with a delayed mandatory compliance date, is authorized as of March 2, 2007. FOR FURTHER INFORMATION CONTACT: John A. Gale or T. Glenn Foster, Office of Hazardous Materials Standards, telephone (202) 366-8553, Pipeline and Hazardous Materials Safety Administration, U.S. Department of Transportation, 400 Seventh Street, SW., Washington, DC 20590-0001, or David Catey, Office of Flight Standards Service, telephone (202) 267-3732, Federal Aviation Administration, U.S. Department of Transportation, 800 Independence Avenue, SW., Washington, DC 20591. SUPPLEMENTARY INFORMATION: List of Topics I. Background II. Safety Issues Associated with the Air Transportation of Compressed Oxygen Cylinders and Oxygen Generators III. Summary of the Final Rule IV. Comments and Regulatory Changes A. General B. Outer Packagings for Compressed Oxygen Cylinders, Other Oxidizing Gases, and Chemical Oxygen Generators 1. Scope of Rulemaking 2. Other Oxidizing Gases Aboard Aircraft 3. Packaging Design Standards 4. Packaging Availability and Costs 5. Compliance Date C. Pressure Relief Device Settings and Authorized Cylinders for Compressed Oxygen and Other Oxidizing Gases D. Limits on Number of Oxygen Cylinders Transported on Aircraft E. Chemical Oxygen Generator Approval V. Effects on Individuals with Disabilities VI. Regulatory Analyses and Notices A. Statutory/Legal Authority for Rulemaking B. Executive Order 12866 and DOT Regulatory Policies and Procedures C. Executive Order 12988 D. Executive Order 13132 E. Executive Order 13175 F. Regulatory Flexibility Act, Executive Order 13272, and DOT Procedures and Policies G. International Trade Impact Assessment H. Unfunded Mandates Reform Act of 1995 I. Paperwork Reduction Act J. Environmental Assessment K. Regulation Identifier Number (RIN) L. Privacy Act I. Background The National Transportation Safety Board (NTSB) determined that one of the probable causes of the May 11, 1996 crash of ValuJet Airlines flight No. 596 was a fire in the airplane's cargo compartment initiated and enhanced by the actuation of one or more chemical oxygen generators carried as cargo in violation of requirements in the Hazardous Materials Regulations (HMR; 49 CFR Parts 171 through 180). Recommendations issued by the NTSB following this tragedy, in which 110 lives were lost, addressed both the initiation of the fire by the improperly packaged generators (which produce external heat when activated) and the possible enhancement of an aircraft cargo compartment fire (of any origin) by the oxygen produced by the generators or other cargo, such as gaseous oxygen in cylinders and other oxidizing agents. In response to the NTSB recommendations, the Department of Transportation has: --Prohibited the transportation of chemical oxygen generators (including personal-use chemical oxygen generators) on board passenger- carrying aircraft and the [[Page 4443]] transportation of spent chemical oxygen generators on both passenger- carrying and cargo-only aircraft [61 FR 26418 (May 24, 1996), 61 FR 68952 (Dec. 30, 1996), 64 FR 45388 (Aug. 19, 1999)]; --Issued standards governing the transportation of chemical oxygen generators on cargo-only aircraft (and by motor vehicle, rail car and vessel), including the requirement for an approval issued by PHMSA [62 FR 30767 (June 5, 1997), 62 FR 34667 (June 27, 1997)]; --Upgraded fire safety standards for cargo compartments on aircraft to require a smoke or fire detection system and a means of suppressing a fire or minimizing the available oxygen, on certain transport-category aircraft [63 FR 8033 (Feb. 17, 1998)]; and --Imposed additional requirements on the transportation of cylinders of compressed oxygen by aircraft and prohibited the carriage of chemical oxidizers in inaccessible aircraft cargo compartments that do not have a fire or smoke detection and fire suppression system [64 FR 45388 (Aug. 19, 1999)]. In the August 19, 1999 final rule, ``Hazardous Materials: Chemical Oxidizers and Compressed Oxygen Aboard Aircraft,'' (Docket No. HM- 224A), we amended the HMR to: (1) Allow a limited number of cylinders containing medical-use oxygen to be carried in the cabin of a passenger-carrying aircraft; (2) limit the number of oxygen cylinders that may be carried as cargo in compartments lacking a fire suppression system and require cylinders to be stowed horizontally on the floor or as close as practicable to the floor of the cargo compartment or unit load device; and (3) require each cylinder of compressed oxygen transported in the passenger cabin or a cargo compartment to be placed in an overpack or outer packaging that meets the performance criteria of Air Transport Association Specification 300 for Type I (ATA 300) shipping containers. In the HM-224A rulemaking, we received more than 55 written comments, and 14 persons made oral statements at a public meeting on January 14, 1998. Based on the comments submitted in that proceeding and our assessment of alternatives, we did not adopt the proposal in Docket No. HM-224A to prohibit all transportation of all oxidizers, including compressed oxygen, on passenger-carrying aircraft. In the preamble to the August 19, 1999 final rule, we explained that testing conducted by FAA indicated the ATA 300 container provides an ``incremental'' level of thermal protection for oxygen cylinders by increasing the time before a cylinder exposed to a fire would release its contents. However, FAA's testing also indicated the risk posed by a compressed oxygen cylinder in a cargo compartment can be further reduced, or even eliminated, if the cylinder is placed in an overpack or outer packaging providing more thermal protection and flame resistance than the ATA 300 containers currently in use. Accordingly, we announced we were ``considering a requirement that an oxygen cylinder may be carried in an inaccessible cargo compartment on an aircraft only when the cylinder is placed in an outer packaging or overpack meeting certain flame penetration resistance, thermal protection, and integrity standards.'' (64 FR 45393). In our earlier June 5, 1997 final rule (also in Docket No. HM-224A), we also indicated we were considering additional packaging requirements for chemical oxygen generators (62 FR at 30769). On May 6, 2004, we published a notice of proposed rulemaking under Docket HM-224B (69 FR 25469). In the NPRM, we proposed to amend the HMR to: (1) Require cylinders of compressed oxygen and packages of chemical oxygen generators to be placed in an outer packaging that meets certain flame penetration and thermal resistance requirements when transported aboard an aircraft; (2) revise the PRD setting limit on cylinders of compressed oxygen transported aboard aircraft; (3) limit the types of cylinders authorized to transport compressed oxygen aboard aircraft; (4) prohibit the transportation of all oxidizing gases, other than compressed oxygen aboard cargo-only or passenger aircraft; and (5) incorporate most of the provisions of an oxygen generator approval into the HMR. II. Safety Issues Associated With the Air Transportation of Compressed Oxygen Cylinders and Oxygen Generators When installed on an aircraft or provided during flight for the use of passengers or crew members, compressed oxygen in cylinders and oxygen generators are subject to requirements in FAA's regulations in Title 14 of the Code of Federal Regulations, and are not subject to the HMR. When transported as cargo, cylinders of compressed oxygen and oxygen generators are subject to requirements in the HMR. Air carriers routinely transport their own oxygen cylinders and oxygen generators as replacement items for use on other aircraft. Some also transport cylinders for their passengers or other customers. Commenters to Docket HM-224A identified a continuing need for the transportation of oxygen cylinders as cargo on both passenger and cargo-only aircraft. As determined through testing conducted by FAA in 1999, cylinders of compressed oxygen release their contents at temperatures well below those that aircraft cargo compartment liners and structures are designed to withstand. When the surface temperature of a cylinder of compressed oxygen reaches approximately 300 [deg]F, the increase in internal pressure causes the cylinder's pressure relief device to open and release oxygen. In addition to the ValuJet tragedy, three accidents and ten incidents involving airplane cargo compartment fires have occurred between 1986 and 2002. While some of these events involved hazardous materials, in some instances the fire was caused by a malfunction of the aircraft's electrical system. The origin of other fires could not be determined. Regardless of the cause of the fire, the presence of an oxygen generator or a cylinder containing oxygen or another oxidizing gas creates the potential for oxygen or another oxidizing gas to be released and to vent directly into a fire, which significantly increases the risks posed by the fire. FAA also found that use of an outer packaging may significantly lengthen the time a cylinder will retain its contents when exposed to fire or heat. Some outer packagings meeting the ATA specification 300 Category I extended the time by up to 60 minutes or more. However, the ATA 300 standard does not specifically address thermal protection or flame penetration. An outer packaging designed to provide both thermal protection and flame penetration could provide even more protection. A copy of the test report is available for review in the public docket. In additional tests conducted in 2002, FAA determined that a sodium chlorate oxygen generator will initiate and release oxygen at a minimum temperature of 600 [deg]F. However, due to uncertainties with other designs and the physical properties of sodium chlorate, the FAA has recommended that oxygen generators not be exposed to temperatures above 400 [deg]F. A copy of this test report is also available in the public docket. This test report shows that an unprotected oxygen cylinder or oxygen generator can quickly and violently release its contents when [[Page 4444]] exposed to temperatures that can be expected from an aircraft cargo compartment fire. III. Summary of Final Rule Because of safety concerns associated with the air transportation of compressed oxygen cylinders and oxygen generators, we are amending the HMR to require cylinders of compressed oxygen and chemical oxygen generators to be transported in an outer packaging that: (1) Meets the same flame penetration resistance standards as required for cargo compartment sidewalls and ceiling panels in transport category airplanes; and (2) provides certain thermal protection capabilities so as to retain its contents during an otherwise controllable cargo compartment fire. The outer packaging standard that is being adopted addresses two safety concerns: (1) Protecting a cylinder and an oxygen generator that could be exposed directly to flames from a fire; and (2) protecting a cylinder and an oxygen generator that could be exposed indirectly to heat from a fire. These performance requirements must remain in effect for the entire service life of the outer packaging. Under this final rule, an outer packaging for a cylinder containing compressed oxygen or another oxidizing gas and a package containing an oxygen generator must meet the standards in Part III of Appendix F to 14 CFR Part 25, Test Method to Determine Flame Penetration Resistance of Cargo Compartment Liners. An outer packaging's materials of construction must prevent penetration by a flame of 1,700 [deg]F for five minutes, in accordance with Part III of Appendix F, paragraphs (a)(3) and (f)(5) of 14 CFR Part 25. In addition, a cylinder of compressed oxygen or another oxidizing gas must remain below the temperature at which its pressure relief device would activate and an oxygen generator must not actuate when exposed to a temperature of at least 400 [deg]F for three hours. The 400 [deg]F temperature is the estimated mean temperature of a cargo compartment during a halon-suppressed fire.\1\ Three hours and 27 minutes is the maximum estimated diversion time world-wide; based on an aircraft flying a southern route over the Pacific Ocean. Data collected during the FAA tests indicate that, on average, a 3AA oxygen cylinder with a pressure relief device set at cylinder test pressure will open when the cylinder reaches a temperature of approximately 300 [deg]F. This result is consistent with calculations performed by PHMSA. In analyzing PRD function, PHMSA calculated that a 3HT cylinder with a PRD set at 90% of cylinder test pressure will vent at temperatures greater than 220 [deg]F. In order to assure an adequate safety margin for all authorized cylinders, including 3HT cylinders, we are amending the HMR to require cylinders of compressed oxygen and other oxidizing gases, which are contained in the specified outer packaging, to maintain an external temperature below 93 [deg]C (199 [deg]F) when exposed to a 400 [deg]F temperature for three hours. --------------------------------------------------------------------------- \1\ The FAA is currently evaluating other non-ozone-depleting suppression agents that could eventually be used in cargo compartments. Some of these agents can maintain an adequate level of safety in the compartment, but the mean temperature may be slightly higher than 400 [deg]F, which is the level found during typical halon-suppressed fires. If an alternate agent is used, the oven soak temperature level may need to be adjusted accordingly. --------------------------------------------------------------------------- IV. Comments and Regulatory Changes A. General PHMSA received comments from 24 entities in response to proposals and specific questions in the NPRM concerning outer packaging, PRDs, authorized cylinders, oxidizing gases aboard aircraft, and chemical oxygen generator approvals. These comments were submitted by representatives of trade organizations, hazardous materials shippers, carriers, and packaging manufacturers, including Airbus, Air Line Pilots Association (ALPA), Air Products and Chemicals, Air Transport Association (ATA), Alaska Airlines, Aviation Excellence, Aviation Mobility, Aviosupport, BE Aerospace, Carleton Technologies, Continental Airlines, Draeger Aerospace, Federal Express (FedEx), International Federation of Air Line Pilots Association (IFALPA), Intertechnique, National Transportation Safety Board (NTSB), Northwest Airlines (NWA), Satair, Scott Aviation (Scott), SR Technics Switzerland, United Parcel Service (UPS), Viking Packing Specialist (Viking), and two individuals. Commenters generally noted our continued efforts to enhance the safe transportation of hazardous materials by air. For example, ALPA applauds our efforts to address the potential hazards associated with oxidizing chemicals, oxygen generators, and gaseous oxygen. Relevant portions of these comments are discussed in the following sections of the preamble. B. Outer Packaging for Compressed Oxygen Cylinders, Other Oxidizing Gases, and Chemical Oxygen Generators In the NPRM, we proposed to require an outer packaging for an oxygen cylinder and a package containing an oxygen generator to meet the standards in Part III of Appendix F to 14 CFR Part 25, Test Method to Determine Flame Penetration of Cargo Compartment Liners. We proposed to require the outer packaging to conform to these performance requirements with no deterioration for its entire service life. We also proposed to prohibit cylinders of compressed oxygen contained in an outer packaging from reaching an external temperature of 93 [deg]C (199 [deg]F)--which is below the temperature at which its PRD would actuate--when exposed to a 205 [deg]C (400 [deg]F) temperature for three hours. We proposed to add a thermal resistance test for packagings for oxygen cylinders and oxygen generators in appendix D to Part 178. We further proposed to remove the limits in Sec. 175.85(i) on the number of oxygen cylinders that may be transported in cargo compartments not equipped with sufficient fire suppression systems. We proposed to allow outer packaging to be built either to the ATA Specification 300 standard or to a UN standard at the Packing Group II performance level. We proposed to authorize only rigid outer packagings for compressed oxygen cylinders. In addition, we proposed one year after publication of the final rule as the mandatory date to comply with the thermal resistance and flame penetration standards for outer packagings for oxygen cylinders and oxygen generators transported on board aircraft. 1. Scope of Rulemaking FedEx and NWA ask PHMSA to reconsider its approach to this rulemaking and begin a more comprehensive assessment with other Federal agencies (including FAA and NTSB), equipment manufacturers, and the air carrier industry. NWA states the requirements on compressed oxygen cylinders proposed in the NPRM are not adequately justified. It differentiates oxygen cylinders from oxygen generators because the latter provide their own heat source and, once initiated, release an uncontrolled flow of oxygen. FedEx suggests the origins and results of cargo compartment fires should be examined in a more comprehensive manner before this rulemaking is implemented. Continental states PHMSA should seek input from both the International Air Transport Association (IATA) and International Civil Aviation Organization (ICAO) regarding the potential impact of the proposed packaging requirement on international regulations and international carriers serving the United States. [[Page 4445]] ATA states thermal protection of oxygen cylinders and oxygen generators does not increase the level of safety under the extreme conditions assumed in test protocols. ATA also states passenger carriers no longer transporting oxygen generators on passenger aircraft due to post-1996 regulations must transport oxygen generators by ground, and ground transportation of oxygen generators in compliance with post-1996 regulations has not resulted in any incidents involving oxygen generators. ATA recommends PHMSA thoroughly review all incidents pertaining to burned aircraft in order to investigate the condition of any oxygen cylinders or oxygen generators that were on board. Aviation Excellence, an aircraft parts distributor holding a Competent Authority Approval to ship oxygen generators (UN3356) questions why the transportation of oxygen generators has become a critical concern, and, along with other commenters, cites ValuJet as the only accident of note involving oxygen generators. This commenter asserts the ValuJet incident was likely due to improper marking and loading, not improper packaging standards, and that thick smoke was the likely cause of the ValuJet incident. Aviation Excellence suggests PHMSA should address the reasons a fire occurred in the cargo bay, rather than what effect the fire had on oxygen, and notes non-hazardous materials, such as rubber and plastic, generate deadly gases and smoke when exposed to fire. Scott notes chemical oxygen generators are currently transported by air as either components or as larger assemblies. When transported as components, the commenter states chemical oxygen generators are cylinders ranging from 2 \1/2\ to 4 inches in diameter and 5 to 11 inches in overall length. The commenter states the size of chemical oxygen generator outer packaging would depend on whether the shipping requirement is for individual generators or a group of generators. Intertechnique also suggests the exception in Sec. 175.501(c) of the HMR allowing a limited number of oxygen cylinders to be transported in the aircraft cabin should recognize that oxygen cylinders used for carrying supplemental oxygen on board frequently have a large capacity, up to 213 cubic feet. Intertechnique states these cylinders must be transported from their respective manufacturing sites to the aircraft manufacturing facility, as well as to and from maintenance facilities, and restrictions on air transportation would increase turnaround times and operational costs when surface transportation is required. Intertechnique also notes that equipment containing an oxygen cylinder must be considered an oxygen cylinder, even when the cylinder is not apparent as in the case of the large number of protective breathing equipment units used on aircraft. We disagree with the commenters' assertions that PHMSA did not conduct a comprehensive assessment before initiating this rulemaking and that the requirements proposed in the NPRM were not effectively justified. The safe transportation of hazardous materials by air is an ongoing area of significant concern for the Department. We regularly assess methods to increase the safe transportation of hazardous materials, and incorporate input from other Federal agencies (including NTSB), equipment manufacturers, and the regulated community as we develop new or revised regulatory requirements. This process was applied to this current rulemaking as well. The FAA and PHMSA have taken a number of steps to reduce the likelihood of a fire on board an aircraft. These include limiting the transport of known flammable materials; imposing restrictions on aircraft systems likely to increase the risk of a fire, requiring increased inspection and maintenance of wiring systems; and incorporating designs to prevent the spread of fire from highly flammable zones. Despite all these measures, it is not possible to totally eliminate fires aboard aircraft. In addition to the risks presented by hazardous materials (whether shipped in violation or conformance with the HMR), structural failures, improper maintenance, and the ignition of non-hazardous materials remain possibilities. For these reasons, we cannot accept claims that PHMSA and the FAA did not conduct a sufficient assessment before initiating this rulemaking. We also disagree with the commenter that suggested we only addressed the reasons a fire occurs in a cargo bay, rather than what effect a fire has on oxygen. A fire in cargo compartments aboard an aircraft can result from several causes, some of which cannot be controlled through regulations, including illegal shipments of oxidizing agents, heat- or fire-producing chemical interaction between certain goods damaged during shipment, or human error. FAA concluded that the use of an outer packaging may significantly lengthen the time an oxygen cylinder or chemical oxygen generator will retain its contents when exposed to fire or heat. The provisions of this final rule will reduce the risk that a fire on board an aircraft will be significantly worsened by the presence of compressed oxygen cylinders or chemical oxygen generators. Because the possibility of fire in a cargo compartment cannot be completely eliminated, the FAA has adopted requirements to mitigate risk and increase the likelihood that a fire can be suppressed and contained long enough to land the aircraft. The FAA has upgraded fire safety standards to require inaccessible cargo compartments on passenger aircraft to have a fire detection and three-hour suppression system, by minimizing the available oxygen (e.g., 14 CFR 25.857(c), 25.858, 121.314(c)). In addition, flame penetration and fire resistance requirements apply to cargo compartments on both passenger and cargo- only aircraft (e.g., 14 CFR 25.855, 121.314(a)). However, these requirements do not, and cannot, address those situations where a fire is actually fed by oxygen provided by other cargo, such as cylinders of compressed oxygen or other oxidizing gases or oxygen generators. Accordingly, as discussed in the ``Background'' section above, we have prohibited the transportation of chemical oxygen generators on board passenger-carrying aircraft and the transportation of spent chemical oxygen generators on both passenger-carrying and cargo-only aircraft, and we issued standards governing the transportation of chemical oxygen generators on cargo-only aircraft, including the requirement for an approval issued by PHMSA. We have also imposed additional requirements on the transportation of compressed oxygen cylinders by aircraft; and prohibited the carriage of chemical oxidizers in inaccessible aircraft cargo compartments that do not have a fire or smoke detection and fire suppression system. The amendments adopted in this final rule are a continuation of our ongoing objective to reduce the risk of another catastrophic event like the ValuJet crash. Because fires on aircraft cannot be totally eliminated, and the consequences of fire in air transportation are far greater than those in highway transportation, an absence of incidents involving ground transportation of oxidizing gases and oxygen generators does not justify postponing these actions. The fact that an oxygen cylinder or generator did not release oxygen during a particular aircraft fire does not diminish the potential for enhancement of a cargo compartment fire by the release of oxygen and the likely consequences. For [[Page 4446]] these reasons, we disagree with the comment that PHMSA should only address the reasons a fire occurs in a cargo bay, rather than what effect a fire has on oxygen. We accept the suggestion that international carriers and international regulations should be considered when undertaking any rulemaking potentially affecting international commerce. The escalating quantity of hazardous materials transported in international commerce necessitates the harmonization of domestic and international requirements to the greatest extent possible. However, we cannot wait for an international agreement when it is necessary to address a known safety hazard. Therefore, we intend to submit a paper to the ICAO Dangerous Goods Panel proposing that the ICAO Technical Instructions be amended consistent with this final rule. We also considered this proposal based on its overall impact on transportation safety and the economic implications associated with its adoption into the HMR. Our goal in this rulemaking is to increase the level of safety for the transportation of oxygen cylinders and oxygen generators currently in the HMR in the most cost-effective manner possible. We believe the adoption of this final rule contributes to meeting that goal. Larger cylinders used as part of an aircraft's supplemental oxygen system (up to 213 cubic feet) makes it impractical for them to be transported (as cargo) in the aircraft cabin under the exception in Sec. 175.501(c). As noted above, when these cylinders are installed on the aircraft, they are not subject to the HMR, nor are Protective Breathing Equipment (PBEs) that are part of the required equipment on board the aircraft--but alternate packagings may be used for these cylinders and PBEs when carried or shipped as replacement items (or company material), ``provided such packagings provide at least an equivalent level of protection to those that would be required by this'' final rule. 49 CFR 175.8(a)(3) (as adopted at 71 FR 14605 [March 22, 2006]). We disagree with the commenter's opinion that thick smoke was the likely cause of the ValuJet incident. First, that view has little support in the NTSB's findings (at p. 134 of the accident report) that ``[o]nly a small amount of smoke entered the cockpit before the last recorded flightcrew verbalization * * * including the period when the cockpit door was open,'' and the ``loss of control was most likely the result of flight control failure from the extreme heat and structural collapse,'' although ``the Safety Board cannot rule out the possibility that the flightcrew was incapacitated by smoke or heat in the cockpit during the last 7 seconds of the flight.'' Moreover, even if the commenter were correct, that circumstance would support the measures we are adopting to prevent the enhancement of a cargo compartment fire (and the associated smoke) caused by the release of oxygen from a cylinder or an oxygen generator. BP Aerospace and Intertechnique recommend an exception from the proposed packaging requirements for cylinders that are nominally empty, with only a small amount of residual pressure, on the ground that the hazards of these ``empty'' cylinders are negligible. BP Aerospace states it is a common practice to transport such cylinders in order to avoid possible contamination of the cylinder from inward leakage. Intertechnique notes many cylinders are shipped before filling (new or repaired cylinders) or after being emptied (for maintenance). Oxygen is a Division 2.2 gas and, as such, is only subject to the regulations when the pressure in the container (cylinder) equals or exceeds 280 kPa (40.6 psia) at 20 [deg]C (68 [deg]F) (see Sec. 173.115(b)(1)). Therefore, oxygen cylinders where the pressure has been reduced to less than 280 kPa (40.6 psia) are not subject to the regulations and are considered to have been purged to the extent necessary for the purposes of Sec. 173.29(b)(2)(ii). In addition, a completely empty cylinder (either new and never filled or purged of all its contents) is not subject to the packaging requirements adopted in this final rule (or to other transportation requirements in the HMR). 2. Other Oxidizing Gases Aboard Aircraft Several commenters also addressed our proposal to prohibit the transportation of all oxidizing gases (other than compressed oxygen) aboard both passenger and cargo-only aircraft. In the NPRM, we discussed our concern that cylinders containing these materials, if exposed to a fire, could intensify the fire to the extent that it would overcome the compartment's halon fire suppression system, penetrate the cargo compartment sidewalls, and cause severe damage or destruction of the aircraft. We stated we had no information to support the need for the following materials to be transported aboard aircraft: ``Air, refrigerated liquid, (cryogenic liquid),'' ``Carbon dioxide and oxygen mixtures, compressed,'' ``Nitrous oxide,'' ``Nitrogen trifluoride, compressed,'' ``Compressed gas, oxidizing, n.o.s.,'' and ``Liquefied gas, oxidizing, n.o.s.'' Air Products expressed agreement with the Department on the need to increase the level of safety in the transportation of oxidizing gases by aircraft, and it states the list should not be limited to oxygen. Air Products suggests materials in Division 2.2 with a subsidiary risk of 5.1 can be transported safely by aircraft and pose no great risk to the aircraft unless the oxidizing material is exposed to abnormally high temperatures over an extended period of time. This commenter suggested packaging performance requirements can be met by limiting the fill density pressure of the oxidizing material and configuring the cylinder so that oxidizing material cannot escape at temperatures up to and including 205 [deg]C (400 [deg]F). Air Products submitted alternative wording for a new section under Sec. 173.302a that would pertain to nitrogen trifluoride and nitrous oxide. Alaska Airlines opposes the proposal to ban Division 2.2 gases with a 5.1 subsidiary risk for transportation by air, stating it is not aware of any experience indicating a safety problem. According to the Alaska Airlines' comments, consumers in Alaska use some of these gases, and in many cases, could not obtain them if not via air transportation. One Anchorage vendor of gas products estimates 20,000 to 50,000 pounds of cylinders of compressed oxygen and nitrous oxide are transported by air every month to medical facilities around the State, with empty cylinders constantly being returned for refilling and return to the hospitals. Alaska Airlines states DOT needs to consider the impact of this proposed rule on the health and welfare of Alaskans, not to mention the subsequent increased cost of medical care. This commenter also notes international regulations identify two additional materials classified as Division 2.2 materials with a 5.1 subsidiary hazard that are permitted on passenger aircraft: ``UN2037, Receptacles, small, containing gas (oxidizing) without a release device, non-spillable,'' and ``UN2037, Gas cartridges (oxidizing) without a release device, non- spillable.'' The commenter concludes that if PHMSA does ban oxidizing gases, it will create additional variances between United States and United Nations dangerous goods regulations DOT has been working to harmonize. The comments summarized above indicate a continuing need for air transportation of most of the oxidizing gases we had proposed to prohibit on [[Page 4447]] aircraft, including Compressed gas, oxidizing, n.o.s.; Nitrogen trifluoride, compressed; and Nitrous oxide. Based on those comments, we conclude we should not prohibit air transportation of these oxidizing gases; however, the same outer packaging standards adopted for cylinders of compressed oxygen and oxygen generators should also be required for these other oxidizing gases. The only exception is that Air, refrigerated liquid (cryogenic liquid), which is already prohibited on passenger aircraft, will also be prohibited on cargo-only aircraft. 3. Packaging Design Standards In the NPRM, we proposed to require a cylinder of compressed oxygen to remain below the temperature at which its PRD would activate, and an oxygen generator not actuate, when exposed to a temperature of at least 205 [deg]C (400 [deg]F) for three hours. ALPA recommends the design standards be raised to 260 [deg]C (500 [deg]F), instead of 205 [deg]C (400 [deg]F), and to 3.5 hours, instead of three hours, in cargo compartments required to have an active fire suppression system, and maintain the knock-down fire status to allow for a safety margin for temperature in excess of the expected mean of 205 [deg]C (400 [deg]F). In addition, Aviation Mobility states there is no aircraft that would survive the extreme conditions for the three-hour duration which the rule would require the cylinder to survive without the actuation of the PRD. We disagree. We continue to believe that these requirements for outer packagings are the most appropriate means to prevent the release of oxidizing gases from a cylinder or chemical generator, which could feed an aircraft compartment fire. The U.S. DOT/FAA Report titled ``Evaluation of Oxygen Cylinder Overpacks Exposed to Elevated Temperature'' (included in the docket of this rulemaking), found that: ``In a Class C compartment, the fire would be detected and agent discharged to extinguish the fire. In the event of a suppressed but not fully extinguished fire, which would be the case if the origin were a deep-seated fire, the temperatures in the compartment could reach 205 [deg]C (400 [deg]F).'' For a deep-seated fire in a Class C cargo compartment, a temperature of 205 [deg]C (400 [deg]F) is the estimated mean temperature of a cargo compartment during a halon-suppressed fire. The FAA test results support our conclusion that a temperature of at least 205 [deg]C (400 [deg]F) is sufficient for the flame resistant penetration test method. In addition, the conditions noted in the NPRM are a worst-case scenario, and were based on a deep-seated fire in a Class C cargo compartment, the duration of which would be the maximum estimated diversion flight time for an aircraft flying a southern route over the Pacific Ocean. However, limiting the requirement for overpacks capable of meeting the three-hour suppression performance standard to overseas flights would be impractical, since this rulemaking anticipates in most instances the overpacks will be provided with the containers, rather than purchased and maintained by an air carrier. Since the initial shipper may not know the final destination of its product, it would also be unable to reliably determine when to use a three-hour overpack as opposed to a one-hour overpack. In any case, applying a lesser fire penetration and thermal protection standard to overpacks because of the shorter flight times to diversion airports in geographic areas other than the South Pacific would undermine the existing rationale behind our requirements that Class C cargo compartments on airplanes be equipped to meet the three-hour fire suppression standard. Therefore, we are amending the HMR to require each cylinder of compressed oxygen remain below the temperature at which its PRD would activate, and that an oxygen generator not actuate, when exposed to a temperature of at least 205 [deg]C (400 [deg]F) for three hours. We also received comments on the proposal to require an outer packaging to be built either to the ATA Specification 300 standard or to a UN standard at the Packing Group II performance level. One commenter (Aviation Mobility) states it encloses oxygen cylinders in a manner that provides safe delivery to the gate and use of the cylinder in the passenger compartment without altering the outer packaging. The commenter notes that, under Special Provision A52 of the HMR, an oxygen cylinder may be carried in the passenger compartment or an inaccessible cargo compartment on a passenger aircraft if it is in ``an overpack or outer packaging that conforms to the performance criteria of Air Transport Association (ATA) Specification 300 for Category I shipping containers.'' The same commenter states its specific outer packaging meets the ATA 300 definition of a ``rigid pack'' and questions whether PHMSA intended any difference in its use of the term ``rigid'' in the NPRM. For clarification, we proposed requiring an outer packaging to be built either to the ATA Specification 300 standard or to a UN standard at the Packing Group II performance level to provide greater flexibility in the design of outer packaging for oxygen cylinders. In the NPRM, we proposed to authorize only rigid outer packagings in order to clarify our original intent to ensure outer packaging provides an adequate level of safety. In addition to meeting the flame penetration and thermal resistance protection requirement, we will continue to require the outer packaging for compressed oxygen cylinders to meet certain performan
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