SFI Specifications

The SFI Foundation, Inc. is an independent organization, which develops implements and administers minimum standards for racing equipment manufacturers. The specification, which covers driving uniforms, is SFI Spec 3.2A.
SFI Spec 3.2A provides for testing of suits in controlled laboratory conditions. Of concern to the race driver is the approximate time a specific garment will provide protection from a second-degree (blistering) burn.
A rating is assigned to a particular type garment of specific construction. The uniforms are categorized with a Thermal Protective Performance (TPP) rating. This rating is expressed as a heat level from which a second-degree burn would probably be incurred.
The SFI 3.2A ranking, the TPP rating and the approximate time to a second-degree burn are tabled above.

If you look at the rating for the 3.2A/5 Spec you'll see that the rating is from 19 TPP to 37 TPP, or roughly 10 to 18 seconds. Most suits produced and sold with an SFI 3.2A/5 are at the lowest level of protection.
For additional information, visit the SFI Foundation link at www.sfifoundation.com