Some of the most common forms of gas utilization equipment are ________.

The correct answer is found in the context of how gas is utilized in various appliances and systems. Gas utilization equipment primarily refers to devices that use gas as a fuel to generate heat or energy for various applications. Air heating, water heating, cooking, and engines are all direct applications of gas utilization.

Air heating systems, such as furnaces or boilers, use gas to provide warmth and comfort in buildings. Water heaters utilize gas to heat water for residential or commercial use. Cooking appliances, including gas stoves and ovens, rely on gas to provide heat for culinary processes. Finally, engines, particularly those used in vehicles or generators, can be designed to run on gas, converting its energy into mechanical work.

This answer encompasses a range of common household and industrial applications, highlighting the versatility and importance of gas in everyday life and various sectors. Understanding these applications is crucial for fire investigation technicians, as they often deal with incidents involving gas appliances and need to understand how they function and their potential hazards.