How is a confined space defined in relation to gas-fired appliances?

A confined space is defined in relation to gas-fired appliances as having a volume less than 50 cubic feet per 1,000 BTU/h of the appliance's input rating. This definition is crucial because it helps determine whether the space has adequate ventilation for safe operation of gas appliances. Proper ventilation is necessary to ensure that combustion air is available for the appliances to function efficiently and to prevent the buildup of potentially harmful gases, such as carbon monoxide.

In a confined space, the limited volume may restrict the availability of combustion air needed by the gas appliance. If the space is insufficiently ventilated, it could lead to incomplete combustion, resulting in dangerous conditions. Thus, understanding this definition helps technicians assess the need for proper ventilation or modifications to the installation to comply with safety standards and regulations.