HVAC H3‑1 Residential and Light Commercial Technical Practice Test 2025 - Free HVAC Practice Questions and Study Guide

In HVAC practice, the classification of a space as "confined" or "unconfined" primarily depends on the volume of air in the space relative to the amount of combustion air required by the appliances present. A confined space is one that does not have enough volume to provide adequate combustion air for the appliances installed, thereby requiring additional ventilation.

When a 100,000 BTU/hr furnace is replaced by a 60,000 BTU/hr furnace, there is a decrease in the total heating capacity within that space. However, if the room had been deemed confined due to the 100,000 BTU/hr unit's demand for combustion air, it remains confined even after the smaller unit is installed. This is because the remaining volume of air may still not meet the combustion air needs for the operational appliance.

In addition, if the space has not been modified to provide additional outside air or sufficient volume, it would still be classified as confined because it does not inherently satisfy the combustion air requirements of the furnace. Therefore, regardless of the decrease in BTU/hr from the furnace, the space continues to be considered confined due to the existing conditions and lack of adequate ventilation.

Thus, the classification of the space remains unchanged, affirming that