If a factory chimney height is lower than 20 m pollution emissions rate for a given substance, the air out of the vent is not more than 50 per cent of emissions from the chimney height 20 meters.
If any plant with a height of 20 meters below the crater, the rate of emission of air out of the chimney must not exceed 50 percent of the emissions from the chimney at a height of 20 meters.
The factory which has a height of the lower 20 meters. Due to the air pollution emission rate from the chimney not exceeding 50 of release rate from the PS box at the height 20 meters.