bestofthebestman
Member
Here are some basic tips regarding filter construction that i am trying to make more easy to access.
This formula was found HERE and i am basing my instructions on a cylindrical filter.
( Fan CFM rating * 0,8267)+77,363=Total area of where air should pass carbon filter
Say you have a 40cfm fan: (40 * 0,8267) +77,363=110 square inches. Not using the formula might have adverse effect on airmovement and smell.
Now say the fan is 4,7 inches in diameter. If you have a cylindrical filter then:
110 / (4,7 * 3,14) = 7,4 inches.
Now you should think about how much carbon to put into the filter. There should be 1.25 ounces per CFM. If 40 CFM fan, then 40 * 1,25=50
There might be different densitys to activated carbon. If its what i have heard, then use (weight of carbon in ounces * 66,75) = volume in gallon. You might have to check this for your self though.
Use this
The volume of your outer cylinder minus your inner cylinder should be atleast as high as calculated earlier, in other words you should have enough volume between the two cylinders to fill enough carbon.
The intake side of the filter should be covered in a material that can filter larger particles not wasting the highly efficcient activated carbon. I would use something thicker than the panty-hoses used in the guide.
Summary
If your are not going to build a cylindrical filter, the formula connecting CFM to filter area still applies.
This formula was found HERE and i am basing my instructions on a cylindrical filter.
( Fan CFM rating * 0,8267)+77,363=Total area of where air should pass carbon filter
Say you have a 40cfm fan: (40 * 0,8267) +77,363=110 square inches. Not using the formula might have adverse effect on airmovement and smell.
Now say the fan is 4,7 inches in diameter. If you have a cylindrical filter then:
110 / (4,7 * 3,14) = 7,4 inches.
Now you should think about how much carbon to put into the filter. There should be 1.25 ounces per CFM. If 40 CFM fan, then 40 * 1,25=50
There might be different densitys to activated carbon. If its what i have heard, then use (weight of carbon in ounces * 66,75) = volume in gallon. You might have to check this for your self though.
Use this
The volume of your outer cylinder minus your inner cylinder should be atleast as high as calculated earlier, in other words you should have enough volume between the two cylinders to fill enough carbon.
The intake side of the filter should be covered in a material that can filter larger particles not wasting the highly efficcient activated carbon. I would use something thicker than the panty-hoses used in the guide.
Summary
If your are not going to build a cylindrical filter, the formula connecting CFM to filter area still applies.
