(a) A Class A condition presents an immediate hazard requiring the operator to shut off the gas and lock the meter, unless the operator can effectively isolate the affected area from the rest of the system.
(b) Class A conditions include, but are not limited to:
(1) any leaking gas piping inside the building which cannot be stopped by temporary or permanent repair means;
(2) any space or water heating appliance that is not properly venting and is discharging carbon monoxide;
(3) any venting system used to convey flue gases, that is defective, obstructed or inoperable; and
(4) heat exchangers which are corroded or cracked beyond repair or blocked and which cause products of combustion to enter the warm air distribution system.