Your garden is a living breathing system that needs to take in fresh air and expel waste air and heat. Intake and exhaust filters can keep your grow from stinking up the neighborhood as well as alerting unwanted pests to your garden's presence.
Most static exhaust filters feature an active carbon ingredient designed to neutralize odor. They come in flange sizes ranging from 4” to 12” in diameter and can be installed very easily to any grow tent or grow room. Ducting length can be up to 60" overall. It’s important to size your filter to the airflow rate of your fans. Adding an exhaust filter to your tent is one of the most important ways to prevent others from detecting your grow. This includes pests such as spider mites that might want to sample your garden before you do. Prevent them from getting in through your exhaust port by installing a filter today. Air in your grow area should be exchanged at least every 5 minutes. If you are using a grow tent that is 5' x 5' x 6' this is 150 sq/ft of air. For optimal air flow, you need a filter and fan that can move between 30 and 60 cubic feet per minute (CFM). It is also important to balance the flow in and out of air. You do not want to create a vacuum inside your grow space. Figure 1 shows several examples of how to setup filters and fans in your grow space or grow tent. We recommend pulling air through your filter and then pushing it out of your grow space or tent. Any of these methods are valid but this way tends to be quieter and reduce odor. Most filters are hung from the ceiling of the grow space to allow more area for plants underneath and to expel warmer air from the top of the grow space, however, heavier filters can be placed on the ground inside of a grow tent that cannot support their weight. All filters should be replaced about once a year. Shaking a filter about halfway through the cycle can expose more activated carbon to improve effectiveness.
CO2 Injection And Filters
It is important to note, if you are injecting CO2 into your grow space, you do not want to exhaust this air out as you will lose the benefits of your injection methods. This is often referred to as a closed loop system since the air continually stays within the room or tent. The best setup in these situations is to scrub the air inside the tent or grow area. Figure 2 shows a typical setup with CO2 generator in the grow space and air scrubber.
While it may not seem necessary to filter incoming air, this is a great way to prevent pests and contaminants from entering your clean grow environment. Spider mites and other insects look for any opening they can find to get into your garden so it’s critical to make sure all openings are filtered. This can also prevent unwanted pollination during your grow cycle. Intake air is also important to rejuvenate CO2 that is consumed during photosynthesis in the grow area if you are not already injecting CO2. Filters should be sized for the draw of air on the tent. You do not want to create a vacuum inside your grow area. If you have a 5' x 5' x 6' tent that is 150 sq/ft of air. Air should be exchanged at least every 5 minutes so you need a filter that will support 30 cubic feet per minute (CFM) or larger depending on your fan speed/volume. A good solution is to always slightly oversize your intake filter so that fresh air intake will always exceed exhaust volume. All filters should be replaced about once a year. Carbon filters should be shaken about halfway through the cycle in order to expose more activated carbon to improve effectiveness.
Ozone Generators are a powerful way to remove odor and cleanse exhaust air. They can be used both inside the tent to maintain air quality or simply on the exit air. The nice thing about ozone generators is that they don’t need to be replaced periodically unlike carbon filters. Ozone generators can be hard on human lungs so it’s best to avoid directly inhaling the air they expel or spending excessive time in grow areas where they are in active use.
See the best ozone generators for your grow.
There are alternative methods of odor control inside your grow tent or grow space. Odor neutralizing gels and mists are an excellent way of passively removing odor without the noise of a fan and the added electrical draw. These methods can be very effective until later in the growing season when plants begin to flower and produce more pollen and resin.
Choosing a fan to match with your filter is important. It can be useful to choose a complete fan/filter package in order to get you growing fast. Packages are sorted by flange diameter size 4", 6", 8",10", and 12" as well as CFM. It can be advantageous to get a larger fan system and then use a fan speed controller to reduce fan speed in order to reduce overall noise. Fan speed can also be varied with different times of the year or growing season in order to more closely simulate outdoor growing conditions. There are a wide range of fan types from blowers to inline fans to axial fans. There are also various ducting, connectors, reducers, and clamps to connect each piece together.
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