Fuel oil is defined as kerosene or any hydrocarbon oil having a flash point not less than what temperature?

Fuel oil is specifically defined in many codes and standards as any hydrocarbon oil, including kerosene, that has a flash point of not less than 100°F. The flash point is the minimum temperature at which a substance can vaporize to form an ignitable mixture in air. For safety purposes, substances with a flash point below 100°F are typically categorized as flammable liquids, while those at or above 100°F are classified as combustible, which refers to their ability to ignite at higher temperatures.

Selecting 100°F as the correct temperature is consistent with regulatory definitions found in standards such as those set forth by the National Fire Protection Association (NFPA) and other fire safety regulations, which help ensure safe handling and storage practices for fuel oils. This categorization is crucial in the context of HVAC and other mechanical industries, as knowledge of fuel properties directly impacts design, installation, and compliance with safety codes.