Here is something that was pulled from the NHRA rule book.
NHRA Helmet Expiration Dates
Label Expires
Snell 2000 1/1/2012
Snell 2005 1/1/2017
Snell 2010 1/1/2022
SFI 31.1A 1/1/2014
SFI 31.2A 1/1/2014
Label Expires
SFI 41.1A 1/1/2014
SFI 41.2A 1/1/2014
SFI 31.1/2005 1/1/2017
SFI 41.1/2005 1/1/2017
SFI 24.1 (JDRL only) 1/1/2015
SFI 24.1/2005 1/1/2017
Structural modifications to helmet/shield are prohibited. Cutting of helmet or helmet shield prohibited. Helmet must remain as manufactured, except for paint scheme/graphics and permitted nonstructural driver modifications to helmet shield as set forth below.
Taping or similar modifications to the helmet shield made by the driver that reduce the drivers field of vision, and are deemed safe by driver in the drivers judgment, are permitted at this time so long as the driver can demonstrate to technical inspectors that the purpose of the modification is to reduce distraction in the drivers field of vision. By using such a modification to the helmet shield, the driver acknowledges and agrees that the driver deems such modification safe in the drivers judgment consistent with the drivers obligations in Section 1, Participant Agreements and
Administrative and Procedural Rules, set forth above, and that the modification does not impair or interfere with the safe operation of the drivers vehicle. See General Regulations 7:8.