Competition Helmets: Helmets meeting SFI Specifications 31.1 (Open Face) and SFI 31.2 (Closed Face) are tested to the highest levels for impact attenuation, penetration resistance, flame resistance and retention capabilites of any helmet in the world. These specifications are very similar to the standards of Snell, which is another helmet standard-setting organization, and are comparable to the Snell "SA" rating.

Sportsman Helmets: Helmets meeting SFI Specifications 41.1 (Open Face) and SFI 41.2 (Closed Face) are tested to the same requirements as Competition Helmets, with the exception of flame testing. This allows for a more economical helmet, with no loss of performance in a non-fire situation. These helmets are comparable to the Snell "M" rating.

Youth Helmets: The SFI 24.1 Youth Helmet specification is new, and specifically addresses the youth market. The extremely stringent test requirements for Competition and Sportsman Helmets forced manufacturers to produce helmets far too heavy for a child's physique to accommodate. In consulation with biomechanical engineers, sanctioning body officials, medical doctors and independent helmet designers, the SFI Helmet Committee developed this standard to provide protection similar to the helmets mentioned above, but designed for smaller drivers.

Many of the test requirements of the Snell SA standard force the manufacturer to build a helmet that is simply too heavy for the undeveloped body structure of a young child. After consideration of this fact (which will be covered in detail later), the SFI Helmet Committee met at the Performance Racing Industry Show in Indianapolis, Indiana in December of 2002.

The Industry was represented by five helmet manufacturers, seven motorsports sanctioning bodies and four internationally acclaimed technical/safety experts who were in attendance. Those people, along with input provided by other experts not attending the meeting, agreed to develop a new specification following the basic design features of the U.S. DOT Spec FMVSS 218 for motorcycles.

This spec concerns itself with not only the impact attenuation as measured in "g's", but also, more importantly, the duration of the impact. This is referred to as the "Wayne State Curve" (shown below), as it was developed by the University. Later research from Japan supports the premise that the head can sustain high "g" loads for very short periods of time. Lower "g" loads, however, must be of a controlled duration, or the result could be concussion, or perhaps, even fatality.

The following are some of the differences between the Snell SA and SFI:

1) SFI 24.1 generally follows the DOT helmet specifications, and requires testing against both flat and hemispherical surfaces. The SFI Specification additionally requires testing against a roll bar structure.

2) Snell uses one drop mass weight for all tests regardless of head size, whereas SFI 24.1 uses the appropriate weight for the head size involved. Remember that SFI 24.1 only uses the two smallest ISO (International Standards Organization) headforms, as that is the relative size of the consumers intended to wear the helmets.

3) The drop distance in SFI 24.1 is less than Snell SA, resulting in lower impact loads. It should be noted, however, that Snell SA helmets are designed for motorsports involving speeds in excess of 200, and even 300, miles per hour. Impacts at these speeds are potentially much greater than for the various applications anticipated for youth helmets, all of which are well under 100 MPH.

4) The Snell test requires that some helmets be tested at temperatures of -22 degrees F, whereas the coldest SFI 24.1 temperature is 14 degress F. The extremely cold Snell standard requires the manufacturer to produce a very hard helmet.

5) The most important item of comparison is the required impact attenuation. Snell specifies test impacts of 300g maximum. A look at the Wayne State curve (above) clearly shows that any 300g exposure in excess of 1 millisecond is "dangerous to life." SFI, on the other hand, also specifies 300g maximum, but follows on with the requirement that "Accelerations in excess of 200g shall not exceed a cumulative duration of 2.0 milliseconds for the first impact, and 2.5 milliseconds for the second impact. Accelerations in excess of 150g shall not exceed a cumulative duration of 4.0 milliseconds." Actual testing to SFI 24.1 has shown no impacts over 250g's, which clearly indicates that the manufacturers are capable of building an appropriate helmet for this application.

The technical comparison could go on for pages, but the important thing to remember is that the SFI Helmet Committee did not want to produce another Snell SA-type spec, as that was felt to be incorrect for the intended user of this helmet. The Committee believes the combination of the DOT, SFI, and ISO requirements is proper and correct.