A gas appliance with 60,000 BTU input requires how much combustion air (cubic feet)?

• A. 3,000
• B. 6,000
• C. 60,000
• D. 30,000

Answer: (A)

Combustion air for an indoor gas appliance is calculated using a simple rule: supply 50 cubic feet of air for every 1,000 BTU per hour of the appliance’s input. This ensures there’s enough oxygen for complete combustion in the space.

For an appliance rated at 60,000 BTU/h, you have 60 units of 1,000 BTU/h. Multiply 60 by 50 to get the required air volume: 60 × 50 = 3,000 cubic feet.

So the space must have at least 3,000 cubic feet of combustion air available. If air is provided differently (such as via outdoor openings or multiple appliances sharing air), the calculation can change, but this rule gives the correct value for a single indoor appliance using the standard indoor-air method.