For a combustion air opening directly to the outside or through a vertical duct, how much space is required per 4000 Btus?

For combustion air openings directly to the outside or through a vertical duct, the requirement is that there must be 1 square inch of opening for every 4000 Btus of input of the appliance. This ensures that there is an adequate supply of oxygen for the combustion process, allowing for the efficient and safe operation of gas appliances.

The measurement of 1 square inch per 4000 Btus is based on industry standards and guidelines to promote proper airflow and prevent issues such as carbon monoxide production, incomplete combustion, and overheating. This standard helps to ensure that gas appliances operate within safe parameters by providing sufficient air for the combustion process.

Understanding this requirement is essential for ensuring compliance with safety regulations and maintaining the efficiency of gas equipment in commercial settings.