SFI 3.2a/5 can be 1, 2 or 3 layer...it’s about the rating not the layers.
I don’t think there’s a 3.2a/2 Rating as listed in the rule book, not sure what that’s about. 3.2a/3 is a rating, but we’ve never run across it.
The SFI 3.2a/1 is typically a single layer suit which people buy with the illusion that they are cooler and cheaper than a multi-layer suit. An SFI 3.2a/1 rated single layer suit can cost between 120.00 and 250.00 from what we’ve seen, ours are from 120.00 to 150. We don’t sell more expensive SFI 3.2a/1 single layer suits because we don’t feel they are good value beyond our price points.
What’s the difference in SFI 3.2a/1 suits? The main difference is the material and country of origin; the suits that are closer to a 100 are likely chemically treated cotton that makes them fire resistant. The upside is they are cheap and will get you through tech, the downside is the treatment seals the material to the point they don’t breathe and the treatment will wash out over time. The more expensive single layer suits could be made from real Fire Retardant Fabric (FPF) which will breathe better and don't lose protection after washing. The minimum protection requirement for a SFI 3.2a/1 suit is 3 seconds(TPP Rating, explained below) before you get a second degree burn…not much time to escape an off road car laying on its roof or side with zip-tied window nets.
I’m not sure why single layer suits are allowed at all, there’s no way to test their effectiveness as it changes with washing.
The SFI 3.2a/5 rated suits are usually 2 or 3 layer, but some of the higher end suits from Sparco and others can be single layer using their proprietary fabrics. Keep in mind that they all have to meet the same minimum requirement associated with the SFI spec. What that means is an SFI 3.2a/5 suit is required to give you 10 seconds before a second degree burn. That said, some exceed the requirement and some will barely pass…but still pass. How can you tell which one exceeds the minimum and which barely passes? Like many things you buy, use advice from a trusted professional combined with common sense. There are lots of good suppliers out there, but there are fortunately many that are just selling “parts” and not safety. Now the infomercial part- We’ve (UPR Division) been in business since 1984, our company has been around since 1960. UPR has always focused on supplying quality safety equipment brands to our customers and most importantly quality advice.
You can buy SFI 3.2s/5 quality entry level Sparco, Alpinestars or RaceQuip racing suits from UPR from 299 to 399. The name brand suits at the lower price points will likely be 2 layer of a thicker material to qualify for the SFI 3.2a/5 rating. If you get into the 500-1000+ price range, you will start to see fabrics that will meet the SFI rating with few layers which makes them lighter weight.
Under-Layers give you one more layer of protection, and a single layer can add up to 6 seconds of protection. A misconception about fire retardant under-layers is that they too hot, the reality is the better brands now breathe way better than the sweaty cotton shirt you’re probably wearing. Approved Under-layers have an SFI 3.3
Thermal Protective Performance (TPP) in the presence of both direct flame and radiant heat. The purpose of the TPP is to measure the length of time the person wearing the garment can be exposed to a heat source before incurring a second degree, or skin blistering, burn.
The TPP rating is the product of exposure heat flux and exposure time. The TPP results can be converted to the time before a second degree burn occurs. The higher the garment rating, the more time before a second degree burn. Here are the SFI ratings with the corresponding TPP values and times to a second degree burn:
