If used in a dirty environment, dirt will collect on the sensor and change the calibration. Corrosive environments will damage the sensor. In a constant flow, the output readings remain constant across a range of temperatures as long as those temperature changes are within the temperature-compensated range. There is no need to correct for humidity because humidity has very little affect on velocity readings. Studies show there is less than a 3 percent change in the velocity reading while the humidity changes from 0 to 100 percent RH in air at room temperature.
Standard velocity is velocity that is referenced to standard conditions.
Density correction equations are used to obtain actual velocity from standard velocity. Actual velocity is the speed at which a microscopic particle of dust would be traveling as the air flow carries it along. Our sensors measure mass air flow velocity which is a measurement of the air mass moving past the sensor. The two measurements give the same readings at standard conditions, but not if pressure or temperature stray from standard conditions. If, for example, the temperature increases, the air would expand and become thinner.