What type of valve is typically used to shut off gas supply in emergencies?

The manual shut-off valve is a critical component when it comes to emergency situations regarding gas supply. This type of valve is designed for human operation, allowing individuals to quickly and easily terminate the flow of gas in case of a leak or other hazardous condition. The manual shut-off valve is typically located in accessible areas to ensure that it can be reached promptly during an emergency.

In contrast, automatic shut-off valves function based on specific conditions, such as pressure changes or specific triggers, which may not always provide immediate action in an emergency. Ball valves, while effective for regulating gas flow, require turning to shut off the gas and may not be as readily available for quick emergency response as manual shut-off valves. Safety relief valves, on the other hand, serve a different purpose; they are designed to relieve excess pressure but do not cut off the gas supply directly.

Therefore, the manual shut-off valve is the appropriate choice for shutting off gas supply in emergencies due to its simplicity and immediacy in operation.