How many inches of free area are needed for ventilation air from a confined space per BTU?

The correct answer addresses the requirement for adequate ventilation in confined spaces where combustion appliances are present. According to building and safety codes, particularly those related to oil and gas heating systems, the size of the ventilation opening needs to be sufficient to provide enough air for combustion.

For a natural gas or oil appliance, the standard guideline is to have 1 square inch of free area for ventilation for every 1,000 BTUs of input. Therefore, if a specific system requires 4,000 BTUs, it would indeed necessitate 1 square inch of free area for every 4,000 BTUs, corroborating that ventilation is crucial for both safety and efficiency.

In this context, the option indicating 1 inch of free area per 4,000 BTU satisfies the ventilation needs for typical combustion operations, ensuring that appliances function correctly and reduce any risks associated with insufficient air supply. This understanding reinforces the importance of adhering to ventilation regulations for safe heating practices.