At present there is no way to measure the average particle size less than 2.5 microns in another way, which is the equivalent to measuring the average particle size less than 2.5 microns, according to the Committee of National Environment 36 (ฺB.E. 2553) to determine the particle size less than 2.5 microns in the general atmosphere. It should therefore be set to use in measuring the average particle size less than 2.5 microns from the measurements by the National Environment Board.