(1) Gas chlorine may be used as a disinfectant only when the main pool recirculation pump is running and circulating pool water and the chlorine supply to the recirculation system is delivered under a vacuum condition.

(2) When compressed chlorine gas is used, whether by an existing pool or spa or on a pool, spa, or other water feature constructed after March 1, 2010, the provisions of (3) through (6) must also be complied with.

(3) The chlorine and chlorinating equipment shall be in a separate, locked, well-ventilated room. Such rooms shall not be below ground level and shall provide positive air pressure with vents near the floor which terminate out-of-doors. The door of the room shall not be open to the swimming pool, but shall open to the outside.

(4) Chlorine cylinders, whether full or empty, shall be anchored to prevent them from falling over. A valve stem wrench shall be present on the chlorine cylinder so that the chlorine supply can be shut off quickly in case of an emergency. A valve protection hood shall be kept in place except when the cylinder is connected.

(5) The chlorine feeding device shall be designed so that in the event of accidents or during interruption of the water supply any leaking chlorine gas will be conducted to the outdoors.

(6) Chemicals must be stored in accordance with the manufacturer's instructions.

(7) Locker style chlorine storage may be used rather than a large room, when practical, following MT-DEQ Circular #1 provisions as well as the rules above.