There is no shortage of carbon scrubbing exhaust filters for cannabis growers. Even the most basic grow setups typically have a carbon scrubber to eliminate exhaust smell.

For some reason, air intake filters are an afterthought in most grow space designs. I think this is because intake filters are difficult to incorporate into grow tents that do not have the same type of airtight seal a rigid plywood grow-box does. As we enter an era of legalization the air intake filter should become more important than the carbon-scrubbing exhaust filter that was designed to hide smells during the prohibition.

Air intake filters remove pollen, mold spores and dust mites. They will even filter bacteria (if you buy a filter with an MER of 13+). I recommend a filter with a MERV of 8 or more (MPR 600+) to filter out mold spores.

In my initial design, I used a waffle style filter that you find in most living room air purifiers.

$20 Air Purifier Filter

This worked well but these filters are expensive and even in a small 2 plant 240 Watt grow I found it to be too restrictive on airflow. I upgraded to furnace filters which are actually cheaper, I guess due to mass production. On Amazon and Costco you can readily find them for under $10 each. Get a filter with an MER of 8+ in order to properly filter out mold spores.

$10 Furnace Filter

I decided to make a frame around the furnace filter for easy removal and so that I could add some light-blocking shutters. This is entirely optional as you could just tape the filter on to the side of your box for installation.

Slide-in Frame to allow for quick changing

My grow box has ambient light around it 24/7 so for good measure I installed light blocking shutters. If you are worried about light leaks you could also get a thicker filter. The filter above is 1″ thick but you can get them up to 4″ thick.





Installed and ready for a filter

Remember this is why we use air intake filters. Buds are sticky and this dust would otherwise have been stuck in your precious nugs!



