Q: We have an old dark room that was converted into an air handler room. What’s the requirement for a door to this room?
A: It all depends where this former dark room is located. First of all, what is the occupancy designation for the building or area where this air handler is located? If it is business occupancy and the air handler does not include a gas-fired furnace, then it is very likely that no door is actually required to this room. However, if the building or area is designated as a healthcare occupancy, then it depends whether or not the room opens up onto a corridor. In healthcare occupancies, all corridors must be separated by walls and doors from all other areas. Now, there are some exceptions to this requirement, but an air handler room will not qualify for any of these exceptions. If the former dark room/air handler room does not open onto a corridor, but opens onto another room, then it is likely that a door would not be required, provided the air handler room does not contain anything to make it a hazardous room, such as fuel-fired equipment, or storage of combustibles of flammables. If the air handler room somehow qualifies as a hazardous room (see sections 184.108.40.206 of the 2000 edition of the LSC) then the room will need to be protected with automatic sprinklers, and the walls will be required to be 1-hour fire rated, and the doors will be required to be ¾-hour rated, self-closing and positive latching. All of that would be required even if the room does not open onto the corridor. If the air handler room is not considered to be a hazardous area, and the room opens onto a corridor, then the door is only required to resist the passage of smoke, or if the corridor is located in a non-sprinklered smoke compartment then a substantial door such as 1¾ inch thick, solid-bonded, wood-core door, or be of such construction to resist fire for at least 20 minutes. Notice it did not say the door had to be 20-minute fire rated. That is a common misunderstanding.