HVAC Journeyman Practice Exam

For appliances located in confined spaces, combustion air openings must be sized at what rate?

1. 1 square inch per 1,500 Btu/h

2. 1 square inch per 2,500 Btu/h

3. 1 square inch per 3,000 Btu/h

4. 1 square inch per 4,000 Btu/h

The correct answer is: 1 square inch per 3,000 Btu/h

The correct choice for the sizing of combustion air openings in confined spaces is based on the fuel-burning appliance's input capacity. Specifically, when appliances are rated based on their BTU input, the correct requirement is to provide 1 square inch of combustion air opening for every 3,000 BTU/h of appliance input. This measurement ensures adequate air supply for proper combustion, which is critical for safety and efficiency. Insufficient combustion air can lead to incomplete combustion, producing harmful gases and decreasing appliance performance. This standard is established to help maintain the correct air-to-fuel ratio, ensuring that the appliance operates safely while minimizing emissions. By following this guideline, HVAC technicians can help ensure that gas appliances operate efficiently and within safety regulations.