(a) No existing flue or gas vent shall be used for any appliance or device not similar in size, character, and type of fuel burned to that previously connected to such flue or gas vent, and no existing flue shall be connected to a newly-constructed fireplace, without the approval of the flue or gas vent for such use or installation by the Commissioner.
(b) All chimneys, smokestacks, flues, smoke pipes, and gas vents shall be maintained in a safe and gas tight condition and the Commissioner may prohibit the use of any appliance or device connected to any chimney, smokestack, flue, smoke pipe or gas vent not so maintained.
(c) Any chimney, smokestack, flue or gas vent which becomes unsafe or dangerous shall be made safe or taken down.