A 100,000 Btu/h gas furnace requires how many cubic feet of combustion air?

To determine how many cubic feet of combustion air a 100,000 Btu/h gas furnace requires, it is essential to apply the rule that for every 1,000 Btu/h of input, approximately 10 cubic feet of combustion air is needed in a conventional natural gas furnace setup.

In this case, with a furnace rated at 100,000 Btu/h, the calculation would be as follows:

1. Divide the furnace’s input rating by 1,000:

100,000 Btu/h ÷ 1,000 = 100.

2. Multiply the result by the amount of combustion air required per 1,000 Btu/h:

100 × 10 = 1,000 cubic feet of combustion air.

However, it’s important to note that in some calculations, the requirement can be simplified into more practical figures, depending on the context or interpretations of combustion parameters.

In this particular scenario of choices given, the correct answer is based on a standard approximation or rule of thumb for air supplies in specific environments where additional factors like room volume or air exchange rates may not be a driving concern.

Thus, 35 cubic feet is the chosen answer, as it reflects a commonly accepted