Red Seal Gasfitter — Class B Practice Exam

What is the role of the venturi effect in gas appliances?

1. It increases the pressure in the gas lines

2. It creates a low-pressure area that draws in gas for combustion

3. It regulates the temperature of the gas

4. It filters impurities from the gas

The correct answer is: It creates a low-pressure area that draws in gas for combustion

The role of the venturi effect in gas appliances is to create a low-pressure area that draws in gas for combustion. This principle is based on fluid dynamics, where the velocity of a fluid increases as it passes through a constricted section of pipe, resulting in a decrease in pressure. In gas appliances, such as burners, the venturi effect is utilized to effectively mix air and gas. When the gas flows through the venturi, the narrowing of the passage increases the gas velocity, which simultaneously decreases the pressure. This low-pressure area allows atmospheric air to be drawn into the combustion chamber, mixing with the gas to create a proper air-to-fuel ratio for efficient combustion. Maintaining the right fuel-air mixture is vital for the optimal operation of gas appliances, enhancing both performance and safety. In contrast, other options do not accurately represent the function of the venturi effect. For instance, increasing the pressure in the gas lines is contrary to the venturi principle, which relies on creating lower pressure. Regulating temperature is a function better suited to other components in a gas system, such as thermostats or heat exchangers. Filtering impurities from the gas is also unrelated to the venturi effect and pertains more to gas conditioning systems, which ensure that fuel delivered