The cabin material flammability tests in FAR 25.853 and Appendix F to 14 CFR Part 25 are a set of seven laboratory tests, and the one that applies to any given part depends on where the part sits in the cabin and, for some tests, how many passenger seats the airplane has. Part I is the Bunsen burner screen that most interior materials must pass. Parts IV and V add heat release and smoke density limits for large surfaces in airplanes with 20 or more seats. Part II is the oil burner test for seat cushions. Part III covers cargo liners. Parts VI and VII cover fuselage thermal and acoustic insulation.1eCFR. 14 CFR 25.853 – Compartment Interiors
Below is what each test measures, what it applies to, and the numbers a specimen has to hit.
Part I Bunsen Burner Tests
Part I uses vertical and horizontal Bunsen burner exposures to check whether a material self-extinguishes after direct flame contact. The flame exposure time and the pass criteria depend on the material’s role in the cabin.
60-Second Vertical Test
Structural interior components get the longest exposure. Ceiling panels, wall panels, partitions, galley structures, large cabinet walls, structural flooring, and stowage compartment materials are held to a Bunsen burner flame for 60 seconds. After the flame is removed, the material must self-extinguish. Average burn length across specimens cannot exceed 6 inches, average flame time after the burner is pulled cannot exceed 15 seconds, and flaming drips must self-extinguish within an average of 3 seconds.2eCFR. 14 CFR Appendix F to Part 25 – Part I
12-Second Vertical Test
A broader list of cabin materials gets a shorter 12-second flame. That list includes floor coverings, textiles such as draperies and upholstery, seat cushion dress covers, padding, coated fabrics, leather, trays, galley furnishings, electrical conduit, air ducting, and trim strips. Average burn length can go up to 8 inches, the 15-second average flame time still applies, and flaming drips get an average allowance of 5 seconds.2eCFR. 14 CFR Appendix F to Part 25 – Part I
Curtains and draperies belong in this 12-second textile category, not the 60-second panel category.
Horizontal Test for Small Parts
Small components that would not meaningfully feed a fire, such as knobs, handles, fasteners, clips, grommets, and small electrical parts, are tested horizontally. The burn rate limit is 4.0 inches per minute.2eCFR. 14 CFR Appendix F to Part 25 – Part I
Parts IV and V Heat Release and Smoke Density
The Bunsen tests show whether a material self-extinguishes. They do not measure how much heat or smoke it produces while burning. For airplanes with 20 or more passenger seats, the large interior surfaces that dominate the cabin have to pass two additional tests.3eCFR. 14 CFR 25.853 – Compartment Interiors
The affected components are ceiling and wall panels (excluding lighting lenses and windows), partitions (excluding transparent safety panels), galley structures including the walls of cart storage cavities, and large cabinets and stowage compartments. Compartments normally closed off by doors, such as lavatories, crew rest quarters, and the cockpit, are exempt.
Part IV Heat Release
Part IV uses the Ohio State University rate of heat release apparatus. A vertical specimen is exposed to a radiant heat flux of 3.5 watts per square centimeter, and the heat it releases as it burns is measured. Two limits must be met at the same time. Total heat release cannot exceed 65 kilowatt-minutes per square meter over the first two minutes. Peak heat release rate cannot exceed 65 kilowatts per square meter at any point during the test. These twin 65/65 limits are the most common compliance hurdle in cabin material development.4eCFR. 14 CFR Appendix F to Part 25 – Part IV
Part V Smoke Density
Part V measures how much smoke a burning material generates. Specimens are tested in accordance with ASTM F814-83 in the flaming mode. The specific optical smoke density, averaged across three specimens, cannot exceed 200 at the four-minute mark.5eCFR. 14 CFR Appendix F to Part 25 – Part V
Part II Seat Cushion Oil Burner Test
All seat cushions except flight crew seat cushions must pass the Part II oil burner test, regardless of passenger capacity.3eCFR. 14 CFR 25.853 – Compartment Interiors It is the most physically aggressive test in Appendix F. The complete cushion assembly is tested with the same foam core, fire-blocking layer if any, dress covering, seams, and closures used in production.
The apparatus is a modified gun-type oil burner delivering a nominal 2.0 gallons per hour of kerosene through a burner cone aimed at the cushion for two minutes. At least three sets of seat bottom and seat back specimens must be tested. Two criteria apply.6eCFR. 14 CFR Appendix F to Part 25 – Part II
Average weight loss across all sets cannot exceed 10 percent, and at least two-thirds of the individual sets must each stay at or below 10 percent. For burn length, at least two-thirds of the sets must show that the burn did not reach the side of the cushion opposite the burner, and no burn length can exceed 17 inches.
If a fire-blocking material is used, it must completely enclose the foam core. Fire blocking is not explicitly required, but in practice nearly every design uses it, because raw foam cannot come close to the 10 percent weight-loss limit on its own.
Part III Cargo Compartment Liner Test
Ceiling and sidewall liner panels in Class C and Class F cargo compartments must resist flame penetration under Part III.7eCFR. 14 CFR 25.855 – Cargo and Baggage Compartments At least three specimens are tested, including any joints, lamp assemblies, or other design features that could weaken containment. They are placed over a kerosene burner rated at 2 gallons per hour. No flame may penetrate any specimen within five minutes, and the peak temperature measured 4 inches above the upper surface cannot exceed 400 °F.8eCFR. 14 CFR Appendix F to Part 25 – Part III
A panel that passes as a ceiling liner may be used as a sidewall liner without retesting.
Parts VI and VII Thermal and Acoustic Insulation
The fuselage insulation blankets between the cabin walls and the aircraft skin were added to Appendix F under 14 CFR 25.856 after the 1998 crash of Swissair Flight 111, effective September 2003.9Federal Register. Improved Flammability Standards for Thermal/Acoustic Insulation Materials Used in Transport Category Airplanes
Part VI Flame Propagation
All thermal and acoustic insulation installed in the fuselage must pass the Part VI radiant panel test.10eCFR. 14 CFR 25.856 – Thermal/Acoustic Insulation Materials The specimen sits in a test chamber, exposed to a radiant heat source calibrated to approximately 1.7 watts per square centimeter at the ignition point, while a pilot burner provides direct flame contact. Flame must not spread more than 2 inches beyond the centerline of the pilot flame, and after the pilot burner is removed any remaining flame on the specimen must extinguish within 3 seconds.
The requirement applies to all transport category airplanes manufactured after September 2005, and to older airplanes whenever their fuselage insulation is replaced.
Part VII Burnthrough Resistance
For airplanes with 20 or more passenger seats, insulation in the lower half of the fuselage must also resist burnthrough under Part VII.10eCFR. 14 CFR 25.856 – Thermal/Acoustic Insulation Materials A modified gun-type burner delivers 6.0 gallons per hour of jet fuel through a large burner cone. Two insulation blanket specimens are mounted at a 30-degree angle and subjected to the flame. Each specimen must prevent fire or flame penetration for at least 4 minutes, and the heat flux measured 12 inches behind the specimen must not reach 2.0 BTU per square foot per second before that time.11eCFR. 14 CFR Appendix F to Part 25 – Part VII
The scenario being simulated is a post-crash fuel fire burning against the outside of the fuselage, with the insulation as the last barrier before the cabin.
Specimen Conditioning and Sample Count
Test results depend on controlled preparation. Specimens must be conditioned at 70 ±5 °F and 50 ±5 percent relative humidity until moisture equilibrium is reached, or for at least 24 hours, whichever comes first.2eCFR. 14 CFR Appendix F to Part 25 – Part I
Most tests require a minimum of three specimens per condition. Part II requires at least three full sets of bottom-and-back cushion pairs, and if the bottom and back use different material combinations, each combination is tested separately as its own set. Specimens must represent the final installed thickness and construction of the actual aircraft component, and they must be marked for traceability back to the production material.
DER Oversight and Compliance Documentation
Test results are recorded in a formal report identifying the specimen, the conditions, and a statement of conformity. For modifications and repairs to existing aircraft, an FAA Designated Engineering Representative (DER) typically oversees the process from test planning through sign-off.
Under FAA Order 8110.113, a DER authorized for flammability work approves the test plan, witnesses the test, handles any specimen nonconformities, and approves the resulting technical data. Before testing begins, the DER confirms that every specimen conforms to the approved descriptive data, verified through a completed FAA Form 8130-9 (Statement of Conformity). The DER also confirms that the test equipment meets applicable regulatory requirements, regardless of whether the facility has been used for previous FAA work.12Federal Aviation Administration. Approval of Flammability Test Data in Support of Major Repairs or Major Alterations
The FAA does not approve or certify flammability test facilities. Verifying that a lab can generate accurate data falls on the DER. If a DER has concerns about a facility’s conformity inspection process or the complexity of the test article, the DER contacts the local Aircraft Certification Office to determine whether a formal FAA conformity inspection is needed. The final compliance finding is recorded on FAA Form 8110-3.13Federal Aviation Administration. Form FAA 8110-3 – Determination of Compliance With Airworthiness Standards
What Failing a Test Costs
Aircraft with non-compliant interior materials can be grounded until the materials are replaced or modified, and non-compliant aircraft often require additional inspections and maintenance to return to service. Repair stations and manufacturers can also face civil penalties. In February 2026, the FAA proposed a civil penalty of nearly $2.84 million against an aircraft repair station for maintenance violations involving the use of expired materials, including adhesives and resins that directly affect flammability-related assemblies.14Federal Aviation Administration. FAA Proposes $2,839,900 Fine Against PEMCO World Air Services for Aircraft Maintenance Violations An entity that receives an FAA enforcement letter has 30 days to respond.