Gas Fitter Practice Test

When using a flue gas analyser that measures CO2, how would you verify the accuracy of the instrument if in doubt?

1. By comparing it to a second sample

2. By comparing it to a known sample

3. By checking it against the gas meter test dial

4. By checking it against the appliance manufacturers maximum input rating

The correct answer is: By comparing it to a known sample

Verifying the accuracy of a flue gas analyser is crucial for ensuring safe and efficient operation of gas appliances. The correct approach involves comparing the analyser's measurements to a known sample, which is a reference that has a precisely defined concentration of CO2. This method allows for an objective assessment of the analyser's performance, ensuring that it is providing accurate readings. Using a known sample means that you have an established benchmark against which to measure the analyser's output. This is especially important in applications where the accuracy of gas readings can impact safety and regulatory compliance. Known samples can come from calibration gases which are manufactured specifically for this purpose and are often certified to ensure their accuracy. In contrast, the other methods, such as comparing to a second sample or checking against a gas meter test dial, may not provide the same level of reliability because they might involve variables that are not controlled or standardized. Additionally, checking against the appliance manufacturers' maximum input rating does not directly evaluate the flue gas analyser's accuracy—it merely provides information on the intended operational limits of the appliance itself.