Red Seal Gasfitter — Class A Practice Exam

What is the function of a backflow preventer in a gas system?

1. To control gas pressure

2. To filter impurities from gas

3. To prevent gas from flowing back into the supply line

4. To regulate the temperature of gas

The correct answer is: To prevent gas from flowing back into the supply line

The primary function of a backflow preventer in a gas system is to prevent the reverse flow of gas back into the supply line, ensuring that the gas remains confined within the intended path of the system. This is crucial for maintaining safety and system integrity, as any backflow could lead to contamination of the gas supply or dangerous gas leaks, posing risks of fire or explosions. Backflow preventers work by utilizing mechanical or check-valve mechanisms that automatically close to stop the backflow if there's a drop in pressure or a change in flow direction. This mechanism is essential in various applications, including gas distribution systems, where maintaining a consistent flow and pressure is crucial for safe operation. While controlling gas pressure, filtering impurities, and regulating the temperature of gas are important aspects of gas systems, these functions are handled by different components, such as regulators, filters, and heat exchangers, rather than the backflow preventer itself. The clear distinction here highlights the importance of understanding each component's role within the overall system.