"Ullage" means the empty volume of a gasoline storage tank system that contains liquid gasoline. For vapor recovery systems, ullage is expressed as accumulated gallons of empty volume for all of the gasoline storage tanks in a certified vapor recovery system.
N.H. Admin. Code § Env-Or 502.31
(See Revision Note #1 and Revision Note #2 at chapter heading for Env-Or 500) #10229, eff 11-17-12