Grow rooms and green houses, particularly at harvest time, may give off all kinds of disagreeable odors. These odors are produced by many vegetables like cabbage etc. at ripening time. Unless removed from the air exhausted from the grow room, the odors can be a nuisance to people in the neighborhood. There are other sources of odor and impurities too, in indoor cultivation that may add to the discomfort like heat and humidity of an indoor environment, pollen, grow media etc. Also since air flow is crucial to crop health and development, proper air circulation has to be maintained to bring in oxygen and carbon dioxide and vent the stale, odor laden air through an exhaust system. It is therefore necessary to filter the air that is vented from the grow room in order to remove odors and impurities.

Activated carbon, with its phenomenal absorbent capacity has long been in use as a purifying agent for air and water. Its action in removing gases, particulate matter and even micro-organisms has found many applications in diverse fields from gas masks for use in wars to absorption of radioactive gases in nuclear plants. Activated carbon filters have also proved very effective in controlling odors from grow rooms and green houses.

Commercial activated carbon usually comes in the form of pellets; these have millions of tiny pores on the surface. These sub-microscopic pores form an extensive network that effectively increases the area of the absorptive surface manifold. Activated carbon works by acting as a very efficient sponge, trapping within its pores all kinds of impurities, gaseous as well as particulate. The smaller pellets have been shown to be especially effective in trapping malodorous contaminants as they leave little space for air to escape through.

Activated carbon is safe and 100% non toxic, therefore it can be used in grow rooms where the cleansed air can be re-circulated. The best results with carbon filters are obtained with these are used in conjunction with an exhaust system, which cleans the air as it leaves the grow room. With this method all stale air gets exhausted and fresh oxygenated, C02 rich air is continually introduced into the grow room.

The typical activated carbon filtering set up comprises an exhaust fan drawing air through the charcoal activated carbon filter. The air is first passed through a poly pre-filter cover that is designed to trap larger particles before it reaches the carbon pellets. When the air passes to the carbon pellets, the odor molecule is scrubbed and drawn out through the exhaust system. The activated carbon air filter and exhaust system should be installed at the highest level in the grow room because warm, odor laden air tends to rise.

High temperatures and humidity adversely affect on the filtration capacity of activated carbon. It becomes important, therefore to adjust air flow into the filter with temperature fluctuations for effective functioning of the filter. One simple control method makes use of a thermostat to adjust the air flow with temperature variations. Besides temperature variations, extremely high levels of relative humidity also lead to diminishing absorption capacity. A relative humidity of 60%, it has been observed, is the upper limit beyond which filtering performance drops sharply. The relative humidity should therefore not be allowed to exceed this limit.

The flow of air inside a grow room is of key importance, especially in an all plastic inside wall environment that is now becoming increasingly popular. Such grow cabinets and grow rooms like Hydrohut tend to give off a plastic smell due to organic deposits on the inside polyurethane walls. Wiping the inside of plastic sheet with paper towels and water removes the offensive deposits and effectively de-odorizes the environment in the grow room.

Other odors can be more persistent in such conditions and the best way to tackle these is to have proper ducting arrangements to ensure optimized air flow. As intake and exhaust vent holes are provided on the grow rooms providing proper ducting is not difficult. Fresh air from outside should be blown in with an adequately sized blower through a duct, through intake hole. Similarly, air to be exhausted should be forced out of the Hydrohut through a charcoal filter with an exhaust blower, through the exhaust vent hole. Fitting a charcoal filter inside the grow chamber will help remove harmful organic molecules. If there are multiple grow rooms in a room, a carbon filter should be placed inside each grow room to avoid air quality problems.

Not using ducting can lead to all types of problems. For instance, blowing in air and not providing a way out by not using ducting will result in the impure air passively finding its way out and then re-entering the grow room. Even in cooler conditions in ocean side towns it is advisable to use proper ducting to ensure intake of fresh air and venting of stale, odor laden air.

Activated carbon filters offer ideal solutions to odor and air borne contaminate removal problems. They absorb impurities to the extent of about 20 to 40% of their own weight. Carbon filters also act against mold and bacterial contamination in greenhouses and grow rooms. There is no residual smell, besides; there is no additional electrical cost for the user associated with incorporating activated carbon filter in the exhaust system. With their 99 % aromatic absorption rate activated carbon filters ensure the removal of all odors from the air. Activated carbon filters are also available in environment friendly models that allow the user to refill or replace the carbon cartridge as necessary.