How to figure for the size of an air filter

[disfunktional]

Is there a formula for figuring the size of a diy air filter?

 

[Rico _El_Guapo]

4x8 space with one light requires 275cfm. This link has an easy to use chart to figure out what side you need. Best bet is to get a fan hooked up to a speed control so you have some wiggle room with the air exchange

 

[disfunktional]

I'm looking more for a formula to figure how much surface area is needed at x amount of thickness. All the calculators that I have found only figure for the size can filter that company is selling. How do they know how much surface area is the correct amount for a specific cfm?

 

[Switcher56]

Figure out the cubic ft of your room.
multiply that # by 2 for ducting losses or by 3 for ducting and filter losses.
Then multiply the result by the # of exchanges an hour: 25, 30 or 60.
Divide the result by 60 = CFM

 

[disfunktional]

Yes sir, I know this formula as well. What I am looking for is the formula to figure how much, or thick of a layer, of activated carbon is needed and how thy figure the cfm rating of the filter

 

[Switcher56]

OH then, it's called trial and error. Dissect a used one (I presume you have a plan) and duplicate it. For what they cost, my time is more valuable than carbon filters

 

[f-e]

50mm bed. That comes from industry, and we should follow it. Some hobby stuff is 30mm but it's no good really.

 

[Switcher56]

2 inc sounds about right.

 

[disfunktional]

Yeah, most of what I am finding is 2" thick too. I have to do a custom build for a tight space and was wondering if anyone knew how the manufactures figure for their sizes

 

[jumpincactus]

yup

yup

OH then, it's called trial and error. Dissect a used one (I presume you have a plan) and duplicate it. For what they cost, my time is more valuable than carbon filters

By the time you pry propietary information from the manufacturers which wont happen, you could just flip the dinero and buy a filter. You must be on a tight budget. :0