Outdoor combustion air must be provided through an opening not less than what size?

Outdoor combustion air must be provided through an opening not less than 3 inches in size. This requirement is based on code specifications that ensure an adequate supply of combustion air for appliances such as gas furnaces, water heaters, and other combustion appliances. The provision of a 3-inch opening ensures that enough air can flow into the space where combustion occurs, allowing for the efficient burning of fuel and preventing issues such as backdrafting or the buildup of harmful gases due to insufficient air supply.

It's important for HVAC professionals to understand this requirement as proper air intake is crucial for the safety and efficiency of combustion appliances. Compliance with this size ensures that appliances operate efficiently while minimizing safety risks associated with inadequate ventilation.