filter carbonWhen you are planning your autoflower closet grow operation you should definitely think about a carbon filter as it is one of the easiest and most efficient odor controlling devices that you can install in your grow room. A carbon filter is made to extract the air that is pushed or pulled trough it from at least 99% of all the chemicals(smells) that are present in the air and that means you can almost completely reduce the smell of growing cannabis. This process will increase the stealthiness of your grow operation as well as increase your comfort level as in the flowering stages autoflowering plants can be quite pungent and produce strong smells that can be annoying and in some rare cases even cause headaches. If you have never used a carbon filter then this guide will we perfect for you as we will look at what are these filters and how do they work as well as proper instructions for installing them.

What is a carbon filter and how it works?

Carbon filters are air filtering devices that use activated carbon to remove various smells trough the chemical absorption process. Activated carbon granules that are used in these carbon filters have a very large surface area. This large surface area comes from the pores inside the carbon molecules and they give about 0.4 km3 surface area in only 450 grams of activated carbon. When air passes trough this activated carbon then the pore structure traps various different chemical molecules that can be anywhere from the size or 0.5 to 50 micrometers and that means that when you install this carbon filter in your grow room any chemicals that your plant produces will be absorbed and won’t get out of your grow box. Usually carbon filters come in a pre-made size and structure with one end sealed with carbon and the other end made to fit ducting or a fan that will suck or push air trough this filter.

Fans for carbon filters

Carbon filters can be mounted with many different fans but most common are inline fans that can be put inside the ducting itself or mounted on the end of a ventilation duct. Because these inline fans are sealed they will not leak any air and that means greater smell reduction with your carbon filter. Usually after you attach a fan to your filter and to the exhaust ducting you should seal it with duct tape or other air tight materials in order to prevent any unwanted air leakage!

When choosing a fan for your filter you need to look at the air movement reading that will come either in CFM (cubic feet per minute) or m3/hr (cubic meters per hour) and then combine this with the reading on your carbon filter that will also tell how much air this filter can clean with the same exact readings. When you choose a fan and a carbon filter for your autoflower grow be sure to get a fan that has a smaller air displacement reading than the one on the filter because the slower the air will go trough the filter the better it will be cleaned. And also remember that adding a filter to your fan will lower the total air displacement by about 10% to 20% depending on the size and efficiency of the filter so keep this in mind when buying a fan and calculating how much air you need to displace to keep your grow room cool.

Negative pressure

When you are using a carbon filter in your grow room or growbox then you need to have a negative pressure inside the growing area where your autoflower plants are located. Negative pressure means that the air pressure or the amount of air molecules inside the grow room is smaller than it is outside this grow room. When you have a negative pressure then air tends to flow in the direction from high to low pressure just like when you blow up a balloon and then open the end and all the high pressure air inside that balloon rushes out into the surrounding area where the pressure is lower. The same exact thing needs to happen with your grow room but you need to create a negative pressure inside the room so the air from the surrounding area will rush in trough all the cracks and openings and in that way will not allow any smells to pass out of the growing area. Negative pressure usually is made with the help of an extraction fan that pulls air out of your grow room creating this pressure difference and when you add a carbon filter before this extraction fan then the only way air can get out of your grow room is trough that filter. And if you understand this process then you should not have any problem with odor control!

Many growers want to create not just an exhaust but also an intake fan but usually this is not necessary as any intake fan will increase that pressure inside the grow room and that can have a negative effect of polluting your house with cannabis aroma. If your exhaust fan is strong enough the negative pressure will suck in fresh and cool air trough all the smaller cracks and opening in your grow closet or grow-room and you will create a self sustaining system.

Pull or push?

filter and fan incorect

filter and fan correct

One of the questions that usually newcomers ask about carbon filters is if you need to pull air trough the filter or push air trough it? The simple answer is that you can do both both the longer answer is that usually manufacturers have designed these units to fit before the extraction fan and you need to pull air trough this filter not push it. Usually carbon filters come with a cotton protective layer that absorbs the larger contaminants and extends your filters lifespan and because this protective layer is mounted on the outside that means that you need to pull air trough your filter and in that way you will first catch all the larger particles with that cotton filter and then all the smaller particles with the carbon itself and the cleaned air will then be vented outside of your grow room. If you reverse the order and put your filter outside the grow room and push air trough it then all those larger molecules will not be filtered trough the cotton and will reduce your carbon filters lifespan as well as any leaks inside the ducting will result in odor getting out of your grow room before it is filtered.

Carbon filter and grow light ventilation

If you have HID grow light inside your grow area then you probably know that they can get quite hot and you need to create a separate or combined ventilation mechanism that will get rid of that excess heat. If you want to combine your HID light ventilation with a carbon filter then you should add a filter then a fan and then push that clean air trough the HID protection tube outside of your grow room and in that way you can keep your grow room cool as well as clean the exhaust air from any smells.

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