SFI 3.2A is the US specification most short-track, drag, oval and club series refer to for driver suits. It sets minimum tests for the suit material, thread, zipper and construction, and grades the suit by how much heat the material holds back before a second-degree burn would occur.
What the specification covers
The specification sets uniform test procedures and minimum standards for driver suits used in competitive motorsport. A suit can be a one-piece garment or a jacket and pants, with fire-resistant cuffs required at the wrists and ankles.
Certification is made by the manufacturer. SFI states that products in the programme are not certified, endorsed or approved by SFI itself: the patch means the manufacturer has represented that the product passed the required tests, and SFI monitors the programme through test reports and audits.
Gloves, underwear, hoods, socks and shoes are associated with a suit but are not rated by 3.2A. They fall under SFI 3.3.
How the rating works
The suit material is tested for Thermal Protective Performance (TPP). The grade printed on the patch is the highest grade whose minimum TPP the material reaches. The rating applies to the material as built, regardless of how many layers it has, and underwear worn beneath the suit does not count towards it.
| SFI grade | Minimum TPP (cal/cm²) | W·sec/cm² |
|---|---|---|
| 3.2A/1 | 6 | 25.1 |
| 3.2A/3 | 14 | 58.6 |
| 3.2A/5 | 19 | 79.6 |
| 3.2A/10 | 38 | 159.1 |
| 3.2A/15 | 60 | 251.2 |
| 3.2A/20 | 80 | 335.0 |
| 3.2A/25 | 100 | 418.7 |
| 3.2A/30 | 120 | 502.4 |
SFI 3.2A Table 1: minimum TPP per grade.
Other tests in the specification
Flammability: each tested layer must average 2.0 seconds or less of after-flame and 6 inches (152 mm) or less of char length, and any melting or dripping fails the test.
Thread heat resistance and zipper heat resistance: the sewing thread and the zipper with its tape are tested separately, and the zipper must not melt, drip, separate or ignite.
Expansion or comfort gussets, where used, must reach the same minimum TPP as the rest of the suit.
Construction points that affect compliance
Closures: zippers must have metal teeth and fire-retardant tape, and any zipper or hook-and-loop closure must be covered by fire-resistant material.
Cuffs at the wrists and ankles are required and must be fire-resistant.
Embroidered logos are permitted by the specification. Stretch panels, gussets and any cool-suit openings must not reduce the suit below its stated rating.
Private label: if a suit is sold under another brand name, the certifying manufacturer must still be identified on a label inside the suit.
Marking and re-certification
The conformance patch is sewn to the left sleeve between the wrist and the shoulder (not on the cuff), or on the back centred no more than 4 inches below the collar. On pants it goes on the left side or rear centre at the belt line.
Suits certified at /10 or higher are inspected every five years by the certifying manufacturer. A suit that passes receives a new conformance label marked with the year of inspection.
3.2A/1 and 3.2A/5 compared
Both ratings come from the same specification and the same tests. The difference is the minimum TPP of the material: 6 cal/cm² for /1 and 19 cal/cm² for /5. In Cuircon's material range, the /1 construction is a single layer of Proban® FR cotton and the /5 construction is a two-layer Nomex® system (see the materials library). Series rules differ: some, such as SCCA time trials, accept /1 only over fire-resistant underwear, and many set /5 as the minimum. Check the rulebook of the series the suit is for.
What buyers should check
- Ask which company is the certifying manufacturer, and check that it appears on SFI's published 3.2A manufacturers list.
- Check that the patch is in the specified position and that the inside label shows the manufacturer and date of manufacture.
- For /10 and higher, check the year of the last inspection.
- Confirm the minimum rating your series requires before ordering.
Sources
Read from the official documents on 8 November 2026. Standards are revised, so always check the current edition and the rules of your series.