How To Build an Inexpensive Carbon Air Scrubber?


Building a carbon scrubber for de-odorizing stinky grows.
The design is such that there is no back pressure on the grow box exhaust fan, and there is maximum surface area for the exhaust air to contact the carbon.

The basic parts list:
2"x2"s and 1/4" plywood sheets, cut to the size of the furnace filters being used
4 furnace filters
4 to 5 lbs. of activated carbon
A set of four casters (wheels)
Duck tape, screws and four *hanger bolts 2" long by 1/4-20 with wingnuts and washers to fasten one removable side for filter servicing.
*Hanger bolts are machine threaded on one end and wood screw threads on the other end.

It starts with the frame construction:
In this example, the measurements of the box, furnace/fibre filters etc…
the scrubber is ~ 17" x 26" x 48" tall… the furnace filters are 16" x 25" x 1", though they are really only 3/4" thick. But again, your design dimensions will depend on the furnace filter size you choose based on the design criteria.

Wheels for mobility, and a wire screen on the bottom to hold the weight
of the de-odorizing filter without the filter buckling.

Using 4 furnace filters and 4 1/2 lbs. of activated carbon to make
a dual layer de-odorizing filter. 2 furnace filters on the bottom,
then a layer of carbon, another furnace filter, another layer of carbon,
and a furnace filter on top.

Carbon layer number one.

Carbon layer number two.

Tape up the carbon/screen layers, and then tape to the base,
creating a completely sealed bottom.

Add the walls and top.

Precut the input air opening before attaching the sides,
and add appropriate interface hardware.

Tape up the box seams with duct tape (the metal tape is best),
and it’s ready for action.

Design criteria and further comments:
The design is solid and works well at eliminating that smell
as long as the following criteria is observed:
For every one (1) cubic feet of exhaust air to scrub:
Have a minimum of 1.25 ounces of activated carbon.
Have at least 8 square inches of filter surface area.

The concept has been tested for several months with multiple grows of the smelliest stuff available. not only does it work well during the grow, but the same technology has been used successfully in drying chambers to eliminate the odor of drying bud (sometimes far worse than the grow itself).

Ionizers are a waste of money to ganja growers. I did try the design with an ionizer inside the enclosure, no difference.
I have also used ozone and found it to be very effective in conjunction
with carbon for larger grows where the design criteria could not be met (too much air flow for the filters used), but the ozone is after the carbon and not before, since carbon absorbs ozone, and i want the carbon to saturate as much as possible with bud stink, then the ozone to clean up the rest.

The carbon is changed every three (3) months or so, and so far, it has not reached saturation within that time period.

Some Q & A about the carbon air scrubber

Why is the box so big?
To eliminate back pressure on the exhaust fan to maximize air movement through the grow box. I am sure the overall dimensions can be scaled down, though I am not sure to what dimensions.

Could you do this to a regular grow box?
Yes, although you want all of the workings in the top of the box. Exhaust fan, carbon filter, etc., venting out of the top of the enclosure.

Where did you purchase the carbon?
The neighborhood fish/aquarium store has the pricey stuff, at around $10+ per 2.25 lbs. It comes alot cheaper, though you might have to change it out more often. Mail-order fish supply places over the net are the way to go when purchasing bulk activated carbon/charcoal.

Author: GeeO


  1. Good setup, But I think that if there was a blueprint or scetch of the finished product it would be easer for one to build. Just a thought.

  2. Sounds like a pretty TIGHT system,, It would be VERY helpful if some sketches or pic’s were included