"External floating roof" means the cover of an open-top storage tank, which consists of a double deck or pontoon single deck that rests upon and is supported by the VOL being contained, and that is equipped with a closure seal to close the space between the roof edge and tank shell.
N.H. Admin. Code § Env-A 1202.64
(See Revision Note at chapter heading for Env-A 1200) #9933, eff 6-1-11