Activated Carbon Filters

Marijuana Horticulture

by Jorge Cervantes

Activated charcoal filters are fantastic, and they work! The charcoal is “activated” with oxygen, which opens millions of pores in the carbon. The activated charcoal absorbs door molecules and other pollutants in the air. The mechanics are simple, and there are three important things to remember when using a charcoal filter.

First, keep room humidity below 55 percent. At about 65-70 percent relative humidity, the charcoal absorbs moisture and cogs. At 80 percent humidity, it stops removing odors.

Second, air must move slowly through charcoal filters to extract odors. The fan on professional units lets just enough air through the filter so the odors have enough (dwell) time to be absorbed by the carbon filter. Third, use a pre-filter. The pre-filter catches most of the dust and airborne pollutants before they foul the carbon filter. Change the pre-filter regularly – every 60 days, or more often if the room is dusty. Carbon lasts about a year. Many growers prefer activated carbon made from coco. Do not use activated carbon that is crushed, because it is less efficient than charcoal pellets.

Install an intake a screen that filters out large particles of dust to prolong the life of the activated charcoal filter. Whether the intake is passive or brought in by a fan, use a filter for incoming air to minimize pollutants in the grow room.

Check with filter manufacturers or retailers about venting specifications for your grow area. A more powerful exhaust fan will be necessary to draw an adequate volume of air through the activated charcoal filter. An adequate airflow is imperative to keep a high CO2 content in the grow room.