Key Takeaways
- The number after the slash (/1, /5, /15…) is the suit's SFI protection level — higher means more protection.
- Each level has a minimum TPP (Thermal Protective Performance) value. TPP ÷ 2 gives roughly the seconds before a second-degree burn.
- SFI 3.2A/1 is the entry level, usually a single layer; SFI 3.2A/5 normally needs a multi-layer construction.
- Your sanctioning body decides the minimum — always check the rulebook for your class before you order.
What SFI 3.2A means
SFI 3.2A is the SFI Foundation specification for driver suits used in auto racing. A suit made to this specification carries a label showing the spec and its protection level, written after a slash — for example SFI 3.2A/1 or SFI 3.2A/5.
The SFI Foundation is a non-profit organisation that publishes standards for motorsport safety equipment. Its specifications are widely used by sanctioning bodies in North America and by many club, drag and circuit racing series around the world. If your series rulebook says "SFI-rated suit required", this is the specification it is talking about.
TPP: the number behind the rating
Every SFI 3.2A level is defined by a minimum Thermal Protective Performance (TPP) value. TPP is measured in a laboratory by exposing the suit's material system to a combination of flame and radiant heat, and recording how long it takes for enough heat to pass through to cause a second-degree burn.
A useful rule of thumb: divide the TPP value by two to get the approximate number of seconds of protection before a second-degree burn. A higher TPP means more time to get out of the car.
The SFI 3.2A levels and their minimum TPP values are:
- /1 — TPP 6 (about 3 seconds)
- /3 — TPP 14 (about 7 seconds)
- /5 — TPP 19 (about 10 seconds)
- /10 — TPP 40 (about 20 seconds)
- /15 — TPP 60 (about 30 seconds)
- /20 — TPP 80 (about 40 seconds)
SFI 3.2A/1: the entry-level certified suit
SFI 3.2A/1 is the base level and is usually achieved with a single layer of flame-retardant fabric. It is the common requirement for club racing, many drag racing classes, track days and entry-level series.
Cuircon's single-layer SFI 3.2A/1 suits are made from 295 g/m² Proban® FR cotton with a TPP rating of 10 — comfortably above the TPP 6 minimum for the /1 level. It is the most affordable route into a certified suit, which makes it a popular choice for teams kitting out several drivers.
SFI 3.2A/5: the multi-layer standard for serious racing
SFI 3.2A/5 requires a TPP of at least 19, which in practice means a multi-layer construction. The air trapped between layers is part of what slows heat transfer, so layering matters as much as the fibre itself.
Our SFI 3.2A/5 suits use a two-layer Nomex® system: a 150 g/m² Nomex® outer shell over a 180 g/m² Nomex® inner layer, 330 g/m² in total, with a TPP rating of 21.6. Nomex® is a meta-aramid fibre with inherent flame resistance — the protection is part of the fibre, not a finish applied to it.
SFI 3.2A/5 is the level most commonly asked for in faster circuit racing classes and in many professional and semi-professional series.
How to choose the right level
Start with the rulebook. Your sanctioning body sets the minimum rating for your class, and some classes or fuel types require a higher level than others. Then consider:
- Speed and fuel load — faster cars and larger fuel loads justify more protection than the minimum.
- Time in the car — endurance drivers spend longer strapped in and may value a lighter multi-layer suit.
- Budget across the team — a team kitting out many drivers may choose /1 for junior or club entries and /5 for its lead programme.
- Underlayers — fire-resistant base layers and balaclavas add protection under any suit.
If you are not sure which level you need, ask us before you order — but always confirm the final requirement with your sanctioning body.
SFI and FIA are different systems
SFI ratings are not interchangeable with FIA homologation. International series run under FIA rules typically require suits homologated to the FIA 8856-2018 standard, which has its own testing and labelling process. A suit built to SFI 3.2A/5 is not automatically FIA-homologated. Read our guide to SFI vs FIA racing suit ratings for the full comparison.
Ordering a certified suit from Cuircon
We manufacture SFI 3.2A/1 and SFI 3.2A/5 suits as stock sizes, private label for your brand, or fully custom to a single driver's measurements. You can colour every panel in our Design Your Suit tool, choose colours from our Nomex colour chart, and send the design to us for a quotation.
Browse our auto racing suits or request a quote with the rating your series requires.
Frequently Asked Questions
What does the /5 mean on an SFI racing suit?+
It is the SFI protection level. An SFI 3.2A/5 suit has a Thermal Protective Performance (TPP) of at least 19, which equals roughly 10 seconds before a second-degree burn in laboratory testing.
Is SFI 3.2A/1 safe enough?+
SFI 3.2A/1 is the minimum certified level and is accepted by many club, drag and track-day series. Whether it is enough depends on your series rules and the speed and fuel load of your car — always check your rulebook.
How is TPP measured?+
The suit's material system is exposed to a combination of flame and radiant heat in a laboratory, and the time until enough heat passes through to cause a second-degree burn is recorded. TPP divided by two gives the approximate seconds of protection.
Is an SFI suit accepted in FIA series?+
Not automatically. FIA series usually require FIA 8856-2018 homologated clothing. Check your series regulations before ordering.
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