Replacing activated charcoal in an air filter

For an activated Charcoal filter:

  1. How long do they typically last?
    2 Is there a way to replace just the charcoal?
  2. For a 2’ X 4’ X 6’ shed, is a six inch filter OK for three to four plants?
  3. Because of high heat, is putting the filter on the floor a good option?
  4. Space is limited, is making my own flat filter to sit on top above the lights worth the cost and trouble?

Thanks in advance,

  1. I’ve heard varied things but I think the best answer is when you start smelling it not working

  2. I think it depends on what type of filter, the ones that are reversible supposedly you can change it, I haven’t tried it yet

  3. yes

  4. No, the higher the better (heat rises, take the heat out from the top of the tent

  5. not sure

-best of luck!