Late last year the SCCA put out this advisory:
SPORTS CAR CLUB OF AMERICA, INC
PO Box 19400, Topeka, KS 66619-0400
DATE: November 16, 2004
FROM: National Staff
TO: All Participants
SUBJECT: Airbag Advisory
It has been brought to the attention of SCCA Technical Services that the use of full-face or closed-face helmets while driving vehicles with active airbag restraint systems may result in injuries in the event of a crash that deploys the airbag.
Because of the location of the steering wheel relative to a driver’s position, the airbag axis is on a level with the driver’s chin. In a crash with airbag deployment, contact with the chin area of a full-face helmet can be so powerful “that the risk of fractures to the jaw cannot be ruled out“ (Hubert Gramling, FIA Institute, FT3/AF, 18.5.1999).
This applies to vehicles that may be used in Solo, RallyCross, High Performance Car Control Clinics, etc.
Therefore, it is highly recommended that full-face helmets not be used in vehicles with functional airbag systems. Potentially more restrictive language is currently being considered for 2005, which could appear in an early 2005 issue of FasTrack. If you have any questions, please contact the SCCA at .
Supposedly they have backed off from this position somewhat and are doing more research. I guess there have been some reports of broken jaws from airbag deployment with full-face helmets. It seems a bit counterintuitive, but apparently open-face helmets allow the airbag to sort of wrap around the face, diffusing the blow somewhat, while the lower part of a full-face helmet can be driven back and concentrate enough force on the chin to break the jaw