The following applies to low pressure steam or Section IV hot water boilers.
Always check with local codes to make sure the following applies!
A boiler may be placed into a room. When the boiler is placed in that room it becomes the “boiler room” and must follow the requirements outlined in section 904 of the Uniform Mechanical Code. Air requirements are based on section 701 and an excerpt can be read here. See examples below.
Example 1: I have a building that is 100’ long x 100’ wide x 20’ tall with no gas fired appliances in it. Can I place a 4,000,000 btu/h input atmospheric low pressure steam boiler in the room without adding combustion air? The minimum required volume is 50 ft3 per 1,000 btu/hr. We take 4,000,000/1,000 which leaves us with 4,000. We multiply 4,000 x 50 to get our minimum volume of 200,000 ft3. Our building is 200,000 ft3 so we meet the minimum requirement.
Example 2: If the Air filtration rate is known, the following calculation can be used. The required volume is (21 Ft3/Air Change per Hour) x (Input of all atmospheric burner appliances in btuh/1000 btuh). If we assume our air change per hour is 1 air change per hour, our equation would be as follows:
(21/1) x (4,000,000/1,000)=
(21) x (4,000)= 84,000 sf3
Our building would be large enough
When is separation required?
Separation is generally required for high pressure steam boilers (Section I) over 10 HP. Again check with local codes to confirm.