A fuel fired boiler that is not listed for closet or alcove installation shall be installed in rooms having a volume at least ________ times the total volume of the boiler.

• A. 8 times
• B. 12 times
• C. 16 times
• D. 20 times

Answer: (C)

When a fuel-fired boiler isn’t listed for closet or alcove installation, the space around it must be large enough to provide ample combustion air and to dilute combustion byproducts. The room volume must be at least 16 times the boiler’s total volume, ensuring there’s sufficient air for efficient burning and safe operation. The boiler’s total volume is the space the boiler itself occupies, and multiplying by 16 gives the minimum required room volume in cubic feet. This larger room helps prevent oxygen depletion and buildup of harmful gases. If the boiler were listed for closet or alcove installation, the required room size could be smaller per the listing, but for an unlisted unit, the 16x rule applies.