What is a requirement when introducing outdoor combustion air into a confined space?

When introducing outdoor combustion air into a confined space, it is essential to ensure that the openings for air supply are appropriately sized to facilitate adequate airflow. This necessity arises from the goal of maintaining an optimum air-fuel mixture for combustion processes while preventing the buildup of harmful gases.

Each opening must be of equal size to ensure balanced airflow, which helps maintain proper ventilation and prevents uneven pressure distribution during operation. This uniformity allows for efficient combustion and avoids scenarios that might lead to the introduction of combustion products back into the space.

Additionally, having equal-sized openings minimizes the risk of one opening becoming a primary air source while others remain less utilized, which could result in negative pressure issues or inadequate air supply in certain areas. This principle is particularly important in gas appliances and installations to promote safe and efficient operation.