Vault and pit sealing, venting, and ventilation

Rule 303. In addition to the requirements contained in 49 C.F.R.§192.187(a)(3), which is adopted by reference in R 460.20606, an operator shall ensure that the outside end of the ventilation ducts of an underground vault or closed top pit is equipped with a suitable weatherproof fitting or vent head designed to prevent foreign matter from entering or obstructing the duct.#

History: 1998-2000 AACS.#