Which type of valve is described as a complete shut-off type safety device for gas-fired heating equipment?

A manual shut-off valve is a critical safety device used in gas-fired heating equipment, designed to fully stop the flow of gas when necessary. This type of valve allows the user to manually open or close the gas supply, making it essential for maintenance, emergency situations, or when the heating equipment is not in use. The ability to completely shut off the gas flow ensures that there are no leaks or hazards, providing a crucial layer of safety in residential and commercial settings.

For gas-fired appliances, there are specific regulations and codes that indicate the need for such a shut-off mechanism, which also facilitates safe servicing and repairs of the system. In contrast, other types of valves, such as ball valves, check valves, and gate valves, may serve different purposes. For example, a ball valve can also provide on/off control but may not always be used solely for safety. Check valves prevent backflow but do not offer a means of isolating the system fully. Gate valves allow for flow regulation but are generally not considered suitable for applications where a complete shut-off is critical due to potential leaks when fully closed. Thus, the manual shut-off valve is the appropriate choice for ensuring complete control over gas flow in heating equipment.