What should be done prior to taking an air velocity reading with an anemometer?

Prior to taking an air velocity reading with an anemometer, it is essential to ensure that all dials are reset to zero. This step is crucial because it establishes a baseline measurement from which accurate readings can be taken. If the dials are not reset, any subsequent readings may be incorrect, as they could reflect previously recorded data rather than the current conditions.

Resetting the dials ensures that any residual values from past measurements do not interfere with the accuracy of new readings. This is particularly important in environments like mines, where accurate air velocity measurements are vital for assessing ventilation and air quality.

While measuring humidity, ensuring equipment calibration, or checking for obstructions are important for other aspects of air quality monitoring, they do not directly pertain to the immediate action required before taking a reading with an anemometer. Each of those steps contributes to the overall reliability of air quality assessments, but resetting the dials is specifically necessary for obtaining accurate air velocity measurements at the moment of testing.