When all combustion air is supplied by a mechanical system, what is the amount of combustion air required per 1000 Btu/hr of appliance input?

The correct answer is based on the standard requirement for combustion air when it is supplied by a mechanical system. For appliances burning gas, such as those fueled by propane or natural gas, it is essential to ensure that there is adequate combustion air for the appliance to function efficiently and safely.

Typically, the industry standard dictates that for each 1,000 BTUs per hour of input, approximately 0.35 cubic feet per minute of combustion air is necessary. This figure ensures that complete combustion occurs, preventing the formation of harmful gases and maximizing efficiency. By providing this volume of air, the system can maintain optimal combustion conditions, which not only ensures efficient operation but also minimizes the risks associated with inadequate air supply, such as soot formation or incomplete combustion.

The other options do not align with this standard, thus highlighting the specific requirement of 0.35 cubic feet per minute per 1,000 BTU/hr as essential for mechanical air supply systems.