The service life and maintenance interval of air filters shall be measured by the gas flow rate of the filter element of the flow filter and the ratio of the gas flow rate required by the engine:

(1) When the flow rate is greater than the flow rate, the filter works normally.

(2) When the flow rate equals the flow rate, the filter should be maintained.

(3) When the flow rate is less than the flow rate, the filter can no longer continue to use, otherwise the working conditions of the engine will become worse and worse, or even unable to work, and new filters need to be replaced.