{"id":"F2005B00954","name":"Civil Aviation Order 108.26 - System specification - Oxygen systems (12/12/2004)","slug":"civil-aviation-order-108-26-system-specification-oxygen-systems-12-12-2004","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":32362,"registerId":"commonwealth-F2005B00954-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"Civil Aviation Order 108.26 - System specification - Oxygen systems (12/12/2004)","content":"Civil Aviation Order 108.26 (as amended)\n\nmade under subregulations 207 (2) and (3) of the Civil Aviation Regulations 1988.\n\nThis compilation was prepared on 2 November 2007 taking into account amendments up to Civil Aviation Order 108.26 Amendment Order (No. 1) 2007.\n\nPrepared by the Legislative Drafting Branch, Legal Services Group, Civil Aviation Safety Authority, Canberra.\n\nContents\n\nSystem specification — oxygen systems\n\nPage\n\n1 Application\n\n2 Abbreviations\n\n3 Oxygen specifications\n\n4 System arrangements\n\n5 Dispensing units\n\n6 Minimum mass flow of supplemental oxygen\n\n7 Protective breathing equipment\n\nAppendix II\n\nNotes to Civil Aviation Order 108.26\n\nSection 108.26\n\nSystem specification — oxygen systems\n\n1 Application\n\n1.1 This section of Civil Aviation Orders contains specifications for aircraft oxygen systems intended for operation at altitudes up to 40 000 feet and is applicable in such circumstances as may be specified by CASA or an authorised person under the Civil Aviation Regulations 1988.\n\n> Note Specifications for oxygen systems in aircraft intended for operations at altitudes above 40 000 feet are subject to separate determination by CASA.\n\n2 Abbreviations\n\n> BTPD means body temperature and pressure dry.\n\n> BTPS means body temperature and pressure saturated.\n\n> STPD means standard temperature and pressure dry.\n\n> (0C. at 760 mm Hg, dry)\n\n3 Oxygen specifications\n\n3.3 (1) Oxygen used in gaseous oxygen systems must comply with a specification acceptable to CASA.\n\nThe following specifications are acceptable:\n\nC.I.G. Gas Code 420 or 430;\n\nRAAF Specification G172;\n\nU.K. Ministry of Defence DEF STAN 68-2 1/1;\n\nU.S. Military Specification MIL-0-272 10.\n\n(2) Oxygen produced by chemical means in an aircraft oxygen system must comply with a specification acceptable to CASA.\n\nThe following specifications are acceptable:\n\nU.S. Military Specification MIL-E-83252;\n\nScott Engineering Report 1024.\n\n4 System arrangements\n\n4.3 Portable oxygen units may be used to meet the crew or passenger breathing requirements.\n\n5 Dispensing units\n\n5.1 An individual dispensing unit must be installed for each occupant for whom supplemental oxygen is to be supplied. A unit must be equipped with a suitable means to retain the unit in position on the face.\n\n5.1.1 A unit:\n\n(a) must not adversely affect a person’s ability to use the aircraft’s electronic communication equipment while using the unit; or\n\n(b) must provide alternative electronic communication equipment that the person can use while using the unit.\n\n5.1.2 The units provided in an aircraft operating at or below flight level 180 must include at least 1 unit designed to cover the nose and mouth for every 15 units provided.\n\n5.1.3 Every unit provided in an aircraft operating above flight level 180 must be designed to cover the nose and mouth.\n\n5.1.4 Every unit installed in an unpressurised aircraft on or after 10 January 1996 must meet the requirements of paragraph 5.1.6.\n\n5.1.5 On and after 10 January 1999, every unit provided in an unpressurised aircraft must meet the requirements of paragraph 5.1.6.\n\n5.1.6 For the purposes of paragraphs 5.1.4 and 5.1.5, a unit meets the requirements of this paragraph if the following information is clearly visible on it:\n\n(a) a notice prohibiting smoking while the unit is used;\n\n(b) an illustration showing how to put the unit on;\n\n(c) a notice describing the dangers of flying with any kind of nasal obstruction or congestion.\n\n5.2 For operations at altitudes up to and including 25 000 feet where section 20.4 of the Civil Aviation Orders requires the use of oxygen, each crew member must be provided with and have readily available, an oxygen supply terminal and dispensing unit. For other occupants under these same circumstances, the supply terminals and dispensing equipment must be located to allow the use of oxygen as required by section 20.4 of the Civil Aviation Orders.\n\n5.3 For operations above 25 000 feet, the provision of oxygen dispensing equipment must meet the following requirements:\n\n(a) an oxygen dispensing unit which is connected to oxygen supply terminals must be immediately available to each occupant, wherever seated. The total number of dispensing units and outlets must exceed the number of seats by at least 10%. The extra units must be as uniformly distributed throughout the cabin as is practicable;\n\n(b) crew members on flight deck duty must be provided with demand equipment. In addition, an oxygen dispensing unit connected to an oxygen supply terminal, must be immediately available to each flight crew member when seated at his station. Where a quick-donning type of oxygen mask is used to meet the requirements of section 20.4 of the Civil Aviation Orders, it must be demonstrated to the satisfaction of CASA that:\n\n(i) the mask is capable of being placed on the face from the ready position, properly secured, sealed, and supplying oxygen on demand, with 1 hand within 5 seconds; and\n\n(ii) the mask can be donned without disturbing eye glasses and without delaying the flight crew member from proceeding with his assigned emergency duties; and\n\n(iii) immediately the donning action is completed, the flight crew member can communicate with other crew members over the aircraft intercommunication system;\n\n(d) portable oxygen equipment must be immediately available for each cabin attendant.\n\n6 Minimum mass flow of supplemental oxygen\n\n6.1 If continuous flow equipment is installed for the use by flight crew members, the minimum mass flow of supplemental oxygen available for each crew member must not be less than the flow required to maintain, during inspiration, a mean tracheal oxygen partial pressure of 149 mm Hg when breathing 15 litres per minute, BTPS and with a maximum tidal volume of 700 cc with a constant time interval between respirations. The flow rates and mask efficiencies in Appendix II may be used instead of the above flow rates.\n\n6.1A In spite of paragraph 6.1, flight crew members may use nasal cannula manufactured under the name “Oxymizer”, subject to the following conditions:\n\n(a) the minimum flow of supplemental oxygen available for each flight crew member at various cabin pressure altitudes must not be less than 0.3 litre per minute at 10 000 feet altitude, increasing by 0.1 litre per minute for every 2 000 feet up to 18 000 feet altitude;\n\n(b) the flight crew members must use the nasal cannula only during private, aerial work, or charter, operations;\n\n(c) the aircraft must not operate above 18 000 feet altitude.\n\n6.2 If demand equipment is installed for use by flight crew members, the minimum mass flow of supplemental oxygen available for each crew member must not be less than the flow required to maintain, during inspiration, a mean tracheal oxygen partial pressure of 122 mm Hg, up to and including a cabin pressure altitude of 35 000 feet and 95 per cent oxygen between cabin pressure altitudes of 35 000 feet and 40 000 feet, when breathing 20 litres per minute BTPS. In addition, there must be means to allow the crew to use undiluted oxygen at their discretion.\n\n6.3 For passengers and cabin attendants using masks, the minimum mass flow of supplemental oxygen available for each person at various cabin pressure altitudes must not be less than the flow required to maintain, during inspiration and while using the oxygen equipment provided, the following mean tracheal oxygen partial pressures:\n\n(a) at cabin pressure altitudes above 10 000 feet up to and including 18 500 feet, a mean tracheal oxygen partial pressure of 100 mm Hg when breathing 15 litres per minute, BTPS, and with a tidal volume of 700 cc with a constant time interval between respirations;\n\n(b) at cabin pressure altitudes above 18 500 feet up to and including 40 000 feet, a mean tracheal oxygen partial pressure of 83.8mm Hg when breathing 30 litres per minute, BTPS, and with a tidal volume of 1100 cc with a constant time interval between respirations. The flow rates and mask efficiencies specified in Appendix II may be used at cabin pressure altitudes up to 25 000 feet instead of the above flow rates.\n\n6.3.1 For passengers and cabin attendants using nasal cannulas manufactured under the name “Oxymizer”, the minimum flow of supplemental oxygen available for each person at various cabin pressure altitudes must not be less than 0.3 litre per minute at 10 000 feet altitude, increasing by 0.1 litre per minute for every 2 000 feet up to 18 000 feet altitude.\n\n6.4 If first-aid oxygen equipment is installed, the minimum mass flow of oxygen available to each user must not be less than 4 litres per minute, STPD. However, there may be a means to decrease this flow to not less than 2 litres per minute, STPD, at any cabin altitude. The quantity of oxygen required may be based upon an average flow rate of 3 litres per minute per person for whom first‑aid oxygen is required.\n\n6.5 If portable oxygen equipment is installed for use by crew members, the minimum mass flow of supplemental oxygen must be as specified in paragraph 6.1 or 6.2 of this section, whichever is applicable.\n\n7 Protective breathing equipment\n\n7.1 Protective breathing equipment must be designed to protect the flight crew from smoke or toxic fumes and gases.\n\n7.2 Equipment must include:\n\n(a) masks either covering the eyes, nose, and mouth or covering the nose and mouth with accessory equipment to cover the eyes; and\n\n(b) at least 1 portable oxygen system of the demand type.\n\n7.3 The protective breathing equipment while in use, must allow the flight crew to use the radio equipment and to communicate with each other, while at their assigned duty stations.\n\n7.4 The part of the protective breathing equipment protecting the eyes must not cause any appreciable adverse effect on vision and must allow corrective glasses to be worn.\n\n7.5 The protective breathing equipment must supply protective oxygen of 15 minutes duration per crew member at a pressure altitude 0 feet with a respiratory minute volume of 30 litres per minute, BTPD. If a demand oxygen system is used, a supply of 300 litres of free oxygen at 20C and 760 mm Hg pressure is considered to be of 15 minute duration at the prescribed altitude and minute volume. If a continuous flow protective breathing system is used (including a mask with a standard rebreather bag) a flow rate of 60 litres per minute at 8 000 feet (45 litres per minute at sea level) and a supply of 600 litres of free oxygen at 20C and 760 mm Hg pressure is considered to be of 15 minute duration at the prescribed attitude and minute volume.\n\nAppendix II\n\n![](image.001.png)\n\nMINIMUM OXYGEN FLOW RATES FOR FLIGHT \nALTITUDES NOT EXCEEDING 25 000 FEET \nWHEN USING MASKS WITH EFFICIENCIES \nEQUAL TO OR BETTER THAN THE A 8 B \nORONASAL MASK, THE SCOTT 28302–11 \nSEMI-DISPOSABLE MASK OR THE K–S \nDISPOSABLE MASK\n\n> Notes to Civil Aviation Order 108.26\n\n> Note 1\n\n> Note: The Civil Aviation Order (in force under the Civil Aviation Act 1988) as shown in this compilation comprises Civil Aviation Order 108.26 amended as indicated in the Tables below.\n\n> Note: > Note: Table of Orders\n\n| Year andnumber | Date of notificationin Gazette/registration on FRLI | Date ofcommencement | Application, saving ortransitional provisions |\n| --------------------- | --------------------------------------------------- | --------------------------- | --------------------------------------------- |\n| CAO 2004 No. R95 | 23 December 2004 | 23 December 2004 (see s. 2) | |\n| CAO 108.26 2007 No. 1 | FRLI 2 November 2007 | 3 November 2007 (see s. 2) | |\n\n```html\n

Table of Amendments

ad. = added or inserted am. = amended rep. = repealed rs. = repealed and substituted

Provision affected

How affected

s. 108.26

rs. CAO 2004 No. R95

subs. 6

am. CAO 108.26 2007 No.1

\n```","sortOrder":0}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"The compilation shows later amendments: the whole section 108.26 was substituted (rs. CAO 2004 No. R95) and paragraph 6 (minimum mass flow provisions) was substituted/amended by CAO 108.26 2007 No.1 (see Table of Amendments and Notes). Those amendments alter the technical minimum flow and related equipment requirements within the Order’s original scope (oxygen systems up to 40,000 ft) rather than expanding the Order beyond that altitude (CASA retains separate determination above 40,000 ft) (sections 1.1; Notes/Table of Amendments; paragraph 6)."},"complexity_factors":["Technical medical/physiological parameters and units (mean tracheal oxygen partial pressure, tidal volume, BTPS/STPD) used to specify flows (sections 6.1–6.3, 6.4, 7.5).","Multiple equipment types and operating modes (continuous flow, demand systems, portable units, Oxymizer nasal cannula exception) with different requirements and limits (sections 5.1–5.3, 6.1, 6.1A, 6.2, 6.5).","Altitude‑tiered rules that change obligations and minimum flows at multiple cabin pressure altitudes up to 40,000 ft (sections 1.1, 6.1–6.3).","Operational and human factors constraints (quick‑donning mask performance, communication while masked, labeling and passenger warnings) that cross technical and procedural compliance (sections 5.1.1, 5.1.2–5.1.6, 5.3(b)).","Distribution and quantity requirements for dispensing units (minimum excess of 10% above seats, uniform cabin distribution) creating logistical compliance implications (section 5.3(a)).","Interplay of national regulator discretion and acceptable specifications (CASA acceptance required for oxygen and chemical‑generation specs; separate CASA determination above 40,000 ft) introducing regulatory judgment (sections 1.1, 3.3(1)–(2)).","Reference to external technical standards and products (military/specification codes, Scott reports, specific mask models and Appendix II flow table) requiring cross‑referencing by implementers (section 3.3, Appendix II).","Amendment history and substitution of provisions (Table of Amendments: s.108.26 rs CAO 2004 No. R95; paragraph 6 substituted/amended CAO 108.26 2007 No.1) which may affect interpretation and compliance timelines (Notes/Table of Amendments)."],"plain_english_summary":"This Order sets technical minimum requirements for aircraft oxygen systems used up to 40,000 feet: what oxygen quality is acceptable, how dispensing and portable units must be arranged, minimum oxygen flow rates for crew and passengers, and protective-breathing equipment standards. It affects aircraft designers, operators, maintenance organisations, flight crew and regulators because it prescribes equipment, labeling and performance thresholds that must be met for safe operation and regulatory compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":6,"scope_assessment":{"changed":false,"description":"The legislation remains focused on its original purpose: technical specifications for aircraft oxygen systems. The 2007 amendment (the only amendment shown) was minor, adding paragraph 6.1A to permit the use of 'Oxymizer' nasal cannulas under specific conditions. This was a targeted technical update rather than scope expansion."},"complexity_factors":["Extensive technical and medical terminology requiring specialised knowledge (e.g., 'mean tracheal oxygen partial pressure', 'BTPS', 'STPD', 'BTPD', 'tidal volume', 'respiratory minute volume')","Numerical specifications with multiple variables: flow rates vary by altitude in 2,000-foot increments, different breathing rates (15, 20, 30 litres per minute), and different equipment types","Nested conditional requirements: rules change based on aircraft type (pressurised/unpressurised), operation type (private/charter/aerial work), altitude thresholds (10,000 ft, 18,000 ft, 18,500 ft, 25,000 ft, 35,000 ft, 40,000 ft), and manufacturing dates (10 January 1996, 10 January 1999)","Cross-references to other Civil Aviation Orders (section 20.4) without reproducing that content","Specific branded equipment exemption ('Oxymizer' nasal cannula) with its own parallel regulatory framework in paragraphs 6.1A and 6.3.1","Alternative compliance pathways: Appendix II allows using specified mask efficiencies instead of calculating flow rates manually","Multiple measurement systems mixed throughout (mm Hg, feet, litres, degrees Celsius, percentages)"],"plain_english_summary":"**What this legislation does**\n\nThis Civil Aviation Order sets out the technical rules for oxygen systems in Australian aircraft that fly up to 40,000 feet. It covers everything from the chemical purity of the oxygen itself to how quickly a pilot must be able to put on an oxygen mask in an emergency.\n\n**Who it affects**\n\n- **Aircraft operators and owners**: Must ensure their planes meet these specifications\n- **Pilots and crew**: Must have properly designed oxygen equipment available and know how to use it\n- **Passengers**: Benefit from rules ensuring oxygen is available if cabin pressure fails\n- **Maintenance engineers and manufacturers**: Must ensure oxygen systems and equipment comply with these standards\n\n**Key requirements**\n\n- **Oxygen quality**: Only certain approved specifications of oxygen can be used (including specific military and commercial standards)\n- **Mask design**: \n - Above 18,000 feet, all masks must cover nose and mouth\n - Below 18,000 feet, at least 1 in 15 masks must cover nose and mouth\n - Masks must not prevent radio communication\n - Masks on newer unpressurised aircraft must carry safety warnings (no smoking, fitting instructions, dangers of nasal congestion)\n- **Emergency speed**: Pilots must be able to don a \"quick-donning\" mask with one hand in 5 seconds without disturbing glasses\n- **Flow rates**: Detailed minimum oxygen flow rates are specified for different altitudes, measured in precise medical terms (tracheal oxygen partial pressure)\n- **Protective breathing**: Special smoke/fume protection equipment must provide 15 minutes of oxygen and allow crew to communicate and wear glasses\n\n**Why it matters**\n\nAt high altitudes, the air is too thin for humans to survive. If cabin pressure fails, supplemental oxygen prevents hypoxia (lack of oxygen to the brain), which causes impaired judgment, unconsciousness, and death. These rules ensure that when seconds count in an emergency, pilots and passengers have equipment that works immediately and effectively."}},"importantCases":[],"_links":{"self":"/api/acts/civil-aviation-order-108-26-system-specification-oxygen-systems-12-12-2004","history":"/api/acts/civil-aviation-order-108-26-system-specification-oxygen-systems-12-12-2004/history","analysis":"/api/acts/civil-aviation-order-108-26-system-specification-oxygen-systems-12-12-2004/analysis","conflicts":"/api/acts/civil-aviation-order-108-26-system-specification-oxygen-systems-12-12-2004/conflicts","importantCases":"/api/acts/civil-aviation-order-108-26-system-specification-oxygen-systems-12-12-2004/important-cases","documents":"/api/acts/civil-aviation-order-108-26-system-specification-oxygen-systems-12-12-2004/documents"}}