CSLB Class B General Contractor's License Practice Exam

In what structure might a furnace explosion occur if combustion air supply is restricted?

1. Living room

2. Garage

3. Closet

4. Basement

The correct answer is: Closet

A furnace explosion due to restricted combustion air supply is most likely to occur in a closet. Furnaces require an adequate supply of air to facilitate the combustion process. If the air supply is obstructed, it can lead to improper combustion, producing excess unburned fuel that can accumulate. Closets are often small and can easily become sealed off, limiting airflow significantly. When there is insufficient air, the combustion process can become unstable, leading to a dangerous buildup of flammable gases. If these gases ignite, it can cause an explosive situation. This risk is less prevalent in areas like living rooms or garages, which typically provide more ventilation and airflow, reducing the likelihood of explosion due to improper combustion. In basements, although there can be limited airflow as well, they often have better ventilation options, making a closet a more probable location for this hazard.