FMVSS 302 Flammability
FMVSS 302 is the U.S. federal standard that governs how fast interior automotive materials are allowed to burn. A material passes when its horizontal burn rate does not exceed 102 mm per minute, or when it stops burning before it reaches the timing zone.
What FMVSS 302 Actually Measures
FMVSS 302 (Federal Motor Vehicle Safety Standard No. 302) regulates the flammability of materials used in the occupant compartment of motor vehicles. It applies to seat cushions, seat backs, headliners, door trim, instrument panels, and any other component within the interior that could be exposed to an ignition source.
The test is a horizontal burn. A specimen is mounted horizontally in a U-shaped holder, and a flame is applied to one end for 15 seconds. After the flame is removed, the test measures how quickly the flame front travels across the specimen between two marked points. The pass criterion is a burn rate not exceeding 102 mm per minute (4 inches per minute). A material that self-extinguishes before the flame reaches the first timing mark also passes.
Why CMVSS 302 Is Part of the Same Conversation
CMVSS 302 is the Canadian Motor Vehicle Safety Standard for interior flammability. It is harmonized with FMVSS 302, using the same horizontal burn configuration, the same specimen geometry, and the same 102 mm per minute limit. A material qualified to FMVSS 302 generally satisfies CMVSS 302, but the submission documentation an OEM requires may still reference both standards explicitly.
ISO 3795 and SAE J369 describe the same horizontal burn method. A program that references any one of these four standards is asking for functionally the same test, though the reporting format and any OEM-specific deviations are defined in the material specification, not in the base standard.
Where OEM-Specific Methods Layer On Top
Most automotive OEMs maintain their own flammability standards that build on the FMVSS 302 baseline. GMW3232, Honda HES C206, and Rivian RTS.1733 are examples of OEM methods that reference the horizontal burn approach while adding their own conditioning requirements, specimen counts, or reporting expectations.
The applicable standard is always defined in the OEM material specification or engineering drawing note. A supplier cannot assume that meeting FMVSS 302 alone satisfies an OEM requirement that calls for a specific internal method. The base burn test may be identical, but the qualification package the OEM accepts is governed by their document, not the federal standard.
| Standard | Role in the flammability stack |
|---|---|
| FMVSS 302 | U.S. federal baseline, horizontal burn, 102 mm per minute limit |
| CMVSS 302 | Canadian equivalent, harmonized with FMVSS 302 |
| ISO 3795, SAE J369 | International and SAE equivalents of the same burn test |
| GMW3232 | GM method built on the horizontal burn |
| Honda HES C206 | Honda method built on the horizontal burn |
| Rivian RTS.1733 | Rivian method built on the horizontal burn |
What Trips Up Flammability Submissions
The most common issue is specimen conditioning. Flammability specimens require conditioning at standard laboratory conditions before testing, and those conditions have to be maintained at the lab immediately before the burn. Materials that arrive without proper conditioning history have to be reconditioned at the lab, which adds time to the program.
The second issue is direction. Some materials burn at different rates depending on orientation, so the specification may require testing in multiple directions. Submitting results for one direction when the spec calls for several leaves a gap that the OEM will catch.
Frequently Asked Questions
What is FMVSS 302?
FMVSS 302 is the U.S. federal safety standard that limits how fast interior automotive materials can burn. It uses a horizontal burn test and sets a maximum burn rate of 102 mm per minute for materials in the occupant compartment.
What is the difference between FMVSS 302 and CMVSS 302?
CMVSS 302 is the Canadian equivalent of FMVSS 302. The two are harmonized and use the same test configuration and pass criteria. OEM documentation may reference both, so suppliers selling into both markets often report against each.
Are FMVSS 302, ISO 3795, and SAE J369 the same test?
They describe the same horizontal burn method with the same core configuration. The technical procedure is functionally identical, though reporting requirements and any OEM-specific deviations are defined in the material specification.
Does passing FMVSS 302 satisfy an OEM flammability requirement?
Not always. Many OEMs require their own method, such as GMW3232 or Honda HES C206, which builds on the FMVSS 302 baseline but adds specific requirements. The OEM material specification defines which method applies.
Ghesquiere Plastic Testing, Inc. is an A2LA accredited testing laboratory in Harper Woods, MI, specializing in weathering and flammability testing for automotive materials. Request a quote at quotes@gptesting.com.
