An unlisted floor furnace must have a temperature limit control that will shut off the gas supply if the air temperature exceeds what level above room temperature?

The correct answer is that an unlisted floor furnace must have a temperature limit control that will shut off the gas supply if the air temperature exceeds 350 degrees Fahrenheit above room temperature. This regulation is in place to ensure safety and prevent overheating, which could lead to fire hazards or damage to the furnace and surrounding structures.

Temperature limit controls are essential in maintaining safe operating conditions in gas appliances. Once the air temperature rises beyond the set limit, the control mechanism activates, automatically shutting off the gas supply. This is a critical safety feature that helps protect both the equipment and the environment in which it operates.

Choosing a threshold like 350 degrees F reflects a balance between effective operation and safety measures, ensuring that the furnace can provide adequate heating without posing risks associated with excessive temperatures.