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By: HTG Supply Melbourne on 08/18/2017

Smells in the garden can be really problematic. When it comes to managing smells in the garden, carbon filters are a must have.

How it Works

The carbon used inside of a carbon filter is activated before it’s put into the canister. That means it is heated up to just the right temperature to cause the carbon to become porous. The pores in the carbon are the real trick to its ability to clean the air. As the air moves through the carbon, the particulate gets caught in the carbon pores. Carbon will absorb almost anything, including moisture, odor particulates, mold and fungus spores, and pollen. As air is pulled through the carbon in the filter, the particulates in the air stick to the carbon and the air coming out of the other end is clean and free of any particulates that might cause odors.

On the outside of a carbon filter is the pre-filter that traps dust and larger particulate that would otherwise clog the pores in the carbon filter faster. Replacing a pre-filter is easy to do, and contributes to the longevity of your carbon filter. It’s recommended to replace your pre-filter once it becomes noticeably dirty. This will allow your carbon filter to work to its full potential.

Use & Maintenance

It’s recommended to use a high-velocity fan to pull the air through your carbon filter. Pulling air opposed to pushing air allows the pre-filter to screen larger particulate before entering into the carbon. Air can also be pushed through the filter, but doing so renders the pre-filter useless, and shortens the life expectancy of the filter. Also, by pulling the air through the filter as opposed to pushing the air through the filter, the air moving through the fan will be cleaner, thus helping your fan run smoother and reducing the amount of moisture that flows through it.

Carbon filters go bad when all of the pores in the carbon (or most of the pores) are filled with particulates, or when air pathways open up for air to flow through untreated. Air will travel the path of least resistance so if the carbon filter isn’t packed correctly, the carbon in the filter won’t work correctly. This is why building your own carbon filters isn’t recommended. It would be a difficult task to replicate the process that a carbon filter company uses to pack their filters at home.

Proper Fan / Filter Sizing

When sizing a fan for your garden, there are a few things that you will want to take into consideration. High-velocity fans are rated in CFM or cubic feet per minute. When deciding which fan to buy, you will need to calculate how many cubic feet the area is that you’re trying to treat. This can be done by multiplying the length x width x height. Since the fan is rated in CFM, the easiest way to figure out which fan will fit your room is to use feet when doing your calculation. (Example 10’x8’x8’ = 640 cubic feet) For optimum cleaning ability, the air in your room needs to be recirculated once every one to three minutes. By dividing your area size by 3, you will have the minimum recommended CFM (Example 640/3 = 213 CFM). An important note to keep in mind is that a filter will add resistance to your fan, and on average, the CFM will drop by ten to twenty percent depending on the filter you choose. So a fan rated at 213 CFM will actually only run at about 192 CFM at most, and as low as 171 CFM with an appropriately sized filter attached.

Carbon filters come in many different sizes and shapes, and there are also lots of fan options on the market. Some manufacturers will give you a recommended fan and filter combination depending on the size of the area that you’re treating. Generally speaking, any six-inch filter and six-inch high-velocity fan should work just fine together, and any combination of four-inch fan and four-inch filter should work well together. The larger the filter you purchase, the more carbon inside of the filter, and the longer the filter will last. However, that rule shouldn’t be taken to extremes. An undersized fan will not be able to effectively pull air through a very large filter, and a lot of the carbon in the filter will not be utilized in that scenario. So matching an eight-inch filter with a four-inch fan may not work out so well.

Scrubbing Carbon Filter Setups

When using a carbon filter as a scrubber, you are not exhausting the air within the room. Your fan is connected to the filter and is pulling air through the carbon filter without exhausting it out of the room. This has the advantage of giving air in the room multiple passes through the carbon filter. As a carbon filter starts to reach the end of its life, air pathways start to form within the carbon, and some of the air will flow through the filter without being cleaned. By giving the air multiple passes through the carbon filter, you are able to better manage smells and extend the life of the filter. This method is also practical for someone using expensive CO2 supplementation, so as not to exhaust the CO2 out of the growing area.

Exhausting Carbon Filter Setups

When using your carbon filter as an exhaust as opposed to a scrubber, after the air is passed over the carbon, it is then expelled out of the room by the high-velocity fan. This method is especially common for a hobbyist grower that is using one fan to cool the lights in the room and run the carbon filter. This is an efficient way to reduce heat and humidity in a garden and manage smells at the same time. Although it may shorten the life of a carbon filter slightly, the benefits can greatly outweigh the shorter life span of the filter by providing an easier way to manage temperature and humidity.

When it comes to managing odors, a carbon filter is simply a must have, and its benefits aren’t limited to just treating smells. We carry a large variety of carbon filters and high-velocity fans here at HTG, and we would be happy to help you figure out which setup would be best for you. Stop in today and or browse our website to check out our selection including fan filter combos from GrowBright that will get the job done at a great price!



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