How many openings are required for combustion air obtained from indoors on the same story?

When combustion air is obtained from indoors for appliances that require it, it is crucial to ensure that adequate air is available for proper combustion. Two openings are required to create a balanced airflow and prevent the risk of negative pressure within the space. This setup allows for the intake of fresh air and the exit of combustion byproducts, thus promoting safety and efficiency.

The first opening serves as the inlet for fresh air, while the second opening acts as an outlet for combustion gases. This design ensures that there is a sufficient exchange of air, reducing the likelihood of backdrafting and improving the overall efficiency of the combustion process. Each opening should connect to outside air, ensuring that there is an adequate supply of oxygen for complete combustion, regardless of any potential obstacles, such as other ventilation systems or structural barriers.

In indoor installations, having two openings also helps accommodate appliances that might intermittently draw air, thus maintaining optimal operating conditions for all appliances in the space. Proper understanding and application of this requirement is essential for compliance with codes and for ensuring safe operation of combustion appliances.