What is the minimum size for a combustion air opening in a confined space?

The minimum size for a combustion air opening in a confined space is determined based on ensuring that there is adequate air supply for proper combustion of gas appliances. When determining the size of combustion air openings, various factors such as the total BTU rating of appliances and the volume of the confined space are taken into consideration.

In many cases, the requirement is set at a minimum of 1 square inch of free area for every 1,000 BTU input of gas appliances in the confined space. This guideline helps to maintain efficient combustion and prevent the buildup of harmful gases. The choice of 100 square inches aligns with standard practices for typical residential applications, ensuring that there is sufficient airflow for appliances to operate safely and effectively.

Choosing a size within minimum standards helps avoid issues like backdrafting or inefficient combustion, thereby prioritizing safety and performance in confined spaces.