[mohd]

A certain volatile substance evaporates from an open container into a room of volume 1000 ft3. The evaporation rate is determined to be 100 mg/min. If the air in the room is assumed to be well mixed, how many ft3/min of fresh air must be supplied to ensure that the concentration of the volatile is maintained below its TLV of 100 ppm? The temperature is 77°F and the pressure is 1 atm. Assume a volatile species molecular weight of 100. Under most circumstances the air in a room cannot be assumed to be well mixed. How would poor mixing affect the quantity of air required?

[macman104]

I can't personally help you myself, but the people that will be able to help you will want to see your attempt first.  On these forums, you need to show some sort of effort, or at least explain what you know and what specifically about the problem you don't get.

[mohd]

i don't get know the law for solving this problom

[Borek]

The only law you will need is the ideal gas equation. Otherwise it is all a simple math.

Hint: calculate mass of the air in the room first.

[mohd]

i got it , thanks guys so much