"Coaxial system" means a type of stage I system which consists of a tube within a tube, such that gasoline is delivered to the gasoline storage tank through the inner tube and the vapors from the gasoline storage tank are returned via the interstice surrounding the fill tube, with a single coupling servicing both the gasoline and vapor recovery hoses.
N.H. Admin. Code § Env-Or 502.07
(See Revision Note #1 and Revision Note #2 at chapter heading for Env-Or 500) #10229, eff 11-17-12