International Building Code Section 907.2.17.1 is hereby amended to read as follows:

[F] 907.2.17.1 Smoke detectors. Not fewer than one smoke detector listed for the intended purpose shall be installed in all of the following areas:

1. Electrical, non-Utility-owned transformer vault rooms, telephone equipment, elevator machine or similar rooms.

2. Elevator lobbies.

3. The main return and exhaust air plenum of each air-conditioning system serving more than one story and located in a serviceable area downstream of the last duct inlet.

4. Each connection to a vertical duct or riser serving two or more floors from return air ducts or plenums of heating, ventilating and air-conditioning systems, except that in Group R occupancies, a listed smoke detector is allowed to be used in each return air riser carrying not more than 5,000 cfm (2.4 m³/s) and serving not more than 10 air-inlet openings.

5. Within 5 feet of doors opening into stairways that are smokeproof enclosures, or that are pressurized stairways.

Where smoke detectors cannot be utilized due to ambient conditions, approved automatic heat detectors shall be installed in accordance with Section 907.4.3.