What is the required clearance for a room heater of circulating type?

The correct clearance requirement for a circulating room heater is indeed 12 inches on the sides and back. This clearance is essential to ensure adequate airflow around the heater, which is critical for safe operation and efficient heating.

Having a minimum distance of 12 inches helps prevent any combustible materials from being too close to the heater, thereby reducing the risk of fire hazards. This clearance allows for proper ventilation, which assists in heat distribution and can help prevent overheating, potentially extending the life of the heater as well.

While other options suggest larger clearances, the standard specification for many types of circulating heaters is typically around 12 inches, making it the balance between safety and practicality.