How air is measured?

Answer 1

Air movement is measured using anemometers. Air speeds inside a building tend to be relatively low, usually less than 1 m/s. This means the anemometers used for this purpose have to be much more sensitive than those used in weather stations measuring wind. There are two main types of internal anemometer, those based on a small propeller and those based on the cooling of a hot metal wire exposed to the air. Propeller based systems tend to be a little less sensitive at very low air speeds, however bearing technology and ultra-lightweight materials are increasingly proving this to be incorrect. Below is a picture of a anemometer.