Room Size for Carbon Filters

Activated Carbon Basics

• Activated carbon removes most hydrocarbons plus many aldehydes and organic acids. It is the most commonly used adsorbent in heating, ventilating and air conditioning systems. Odors and air pollutants adhere or cling to the surface of porous particles of charcoal.

Activated Carbon Efficiency

• One pound of activated carbon adsorbs from 20 to 40 percent of its weight. One gram of activated charcoal has roughly the same surface area as the goal line to the 10-yard-line of an American football field. Put another way, one pound of activated charcoal has the surface area of 60 to 150 acres. The effectiveness of an activated charcoal filter depends on the rate of the air being vented from a room or re-circulated through it.

Venting Requirements

• Activated charcoal filters typically filter 99.5 percent of volatiles from the air. A room that is 10 feet wide, 12 feet long and has a ceiling 8 feet high contains 1,000 cubic feet. A filter that removes 99 percent of the particles from air removed at the rate of 10 cubic feet per minute will be 10 times more efficient if the air is removed at 100 cfm. A general estimate is that you should change the volume of a hydroponic grow room eight to 10 times per hour. If you are venting and replacing grow room air, you have to be careful that this does not cause the temperature to drop below 72 degrees Fahrenheit. For home use, changing the air six times an hour is sufficient.

Air Path

• Activated carbon filters are commonly available to fit vent fans from 4 to 12 inches in diameter. More activated charcoal filters and a more frequent change of air is needed for a given space if the cleaned air is re-circulated. If the air is removed after it is filtered and fresh air brought in, then fewer and smaller filters are needed.