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Environmental Controllers and CO2 Enrichment

in The Basics of Hydroponics .

What Needs Controlling?

The environment is an important factor in the growth of plants and optimal results will be obtained by keeping the environment at the specific plant’s desired temperature and humidity. Although temperature and humidity are important, some of the biggest problems come from poor ventilation and/or not enough carbon dioxide. Poor ventilation may be the direct cause of a lack of CO2 because the plants uptake it all and there isn’t any source of CO2.environmental controllers Carbon Dioxide is very prevalent in our atmosphere, so simply ventilating outdoor air through the room will treat any CO2 deficiency you may have. Supplementing CO2 will be discussed below. Venting air will also regulate your temperature and humidity, so it’s a win-win, if you can support that.

Another route you could go is the automated controller one. The expense may well be worth its while because having the perfect conditions leads to a plant’s optimal potential yield. Of course, this is if you automate every aspect (CO2, nutrients, pH, etc.) of your growing environment. This type of automation is typically associated with commercial growers who cannot efficiently maintain hundreds of plants by themselves, but it could still be beneficial for a small grower who is just simply trying to get the best possible yield.

Air Circulation

The movement of air in your indoor growing environment is very important and could mean life or death for your plants. Not having enough fresh air circulating through the room could lead to a carbon dioxide deficiency in your air which will leave your plants unable to breathe and heavily stress them. They breathe through the stomata on the undersides of their leaves, so optimal circulation will bring fresh CO2 to the bottom of the leaves. A simple oscillating fan will easily solve this fresh air problem, but you will need an air source coming from outside of the room (unless you are supplementing with a CO2 tank).

A good way to have your air circulating is in a circle around the room. This will allow all the fresh air to come in and the stale air to naturally flow out. Having a fan blowing in fresh air is the only completely necessary thing, however. If you point the fan at your plants, it will be circulating in fresh air as well as strengthening the plant’s stems by emulating wind.

Temperature and Humidity Control

  • This section is under the assumption that you aren’t supplementing with CO2. If you are, then keep reading the sections below for tips on regulating CO2.


Temperature and humidity can get out of hand pretty quickly because of your HID lighting and the plants respiratory process. Therefore, it is important to have a plan to exhaust extra heat and humidity. The easiest way to do this is to have a vent fan on a timer, periodically exhausting all the air in the room. An intake fan can be added to this setup which brings in cooler air from outside of the room. While this would be better than having no system, it is still not an optimal or even efficient way of cooling and dehumidifying.

Another method of reducing the humidity of your room is to have an automated controller which detects relative humidity and reduces humidity when a maximum percentage is reached. This is a very efficient way of reducing humidity because it won’t activate until it has actually exceeded the limit you set.

If you are looking for something that doesn’t cost a fortune but gets the job done right, a dehumidifier is the obvious choice for reducing your humidity.

For problems with heat, there are a couple of options to choose from. You can get a vent fan with a thermometer that automates the action of the fan. This way when the temperature surpasses a certain threshold the fan will turn on and vent the hot air out of the room. Another option is based on if your reflector has built in venting properties. If this is the case, hooking air ducting up to these vents and up through the ceiling, all while attached to an inline fan, will suck the extremely hot air generated by your HID lamp up and out of the hood before it saturates the room with heat.


Venting through ducting can only be accomplished with the use of at least one exhaust fan. Two would be better, but only one is truly necessary. You also have the option of only attaching one side to ducting and leaving the other side open for the room air to be brought through. This sounds like it would very effectively treat heat problems, which it would, but it would cause all your air conditioned air to be sucked out of the room, vastly increasing your electric bill. A better solution is to simply run ducting from above the ceiling because although this will be hotter air, it will still flow the even hotter air given off by the light out of the room. Odors can be removed with a carbon filter or an ozone generator, but ozone could be harmful to human lungs.

A good measure to go by on how strong of a fan you should get is to calculate the area of your space and have that space able to be ventilated in 5-7 minutes. This means for a 1000 cubic square foot area you should preferably get a 200 CFM (Cubic feet per minute) fan. This will allow your space to be cleared out quickly and efficiently, in exchange for the outdoor fresh air.

CO2 Enrichment

Enriching your grow environment with carbon dioxide can be a vital improvement to the growth speeds of your plant. Some people report up to 100-200% increases in growth due to the very nature of plants: Their photosynthesis relies on carbon dioxide amongst water and light for growth. Another fact: The air around us contains about 310-590 ppm of carbon dioxide, but plants can benefit from 1000 up to 2000 ppm of CO2! That’s around 4 times the amount of carbon dioxide being used by the plants for their energy. This is dramatic and the results are actually surprisingly low for the actual increase in uptake of CO2. You would think that 4 times the energy input would equal 4 times the energy and hence 4 times the growth, however, it unfortunately, but still magnificently grows probably an average of 50% faster, which is huge.

When enriching with CO2, it is important to have your temperature raised a little bit. They need the extra heat to increase their metabolism in order to account for the extra CO2. The process of photosynthesis has a byproduct of pure oxygen. This will make your humidity increase dramatically so it is important to have things that will counteract that humidity which will promote mold in the flowers. A dehumidifier would be a good place to start.

Using Bottled CO2

The most common way of supplementing CO2 is to use a tank full of the gas. You simply attach a CO2 regulator to the tank and set it to a certain level that corresponds to the ppm level you want it to have. CO2 will be released and because it is heavier than oxygen, it will pool at the bottom of your room. Therefore, it will be necessary to have a means of pushing or bringing that CO2 up into circulation.

A couple of ways to do this are:

  1. To have a fan blowing upwards under your CO2 pointed right at the plants to ensure they at least get it initially.
  2. Have an industrial type fan sitting at the bottom of your room blowing straight up or angled to circulate the air throughout the grow room.
  3. Have your CO2 tank attached to a hose with holes in it which lines the top of your grow area, allowing the CO2 to gently fall onto your plants.

One major upside to using bottled CO2 is that it does not cause excess heat, however, this may be wanted in some scenarios. A downside is that CO2 tanks must be replaced on a regular basis, depending on how many plants you have.

CO2 Generators

These work by burning natural gas, propane, butane and alcohol. If your fuel is burning red or orange, it is giving off carbon monoxide which is NOT wanted. You want a blue or colorless flame that gives off carbon dioxide. The advantage this has over CO2 tanks is that you can simply pull it from your building, because most have a natural gas line. This makes it cost effective, however, getting a professional to install it could be a safe way to go about this.

The generators have a pilot flame which lights the gas as it is slowly released from the generator. Also, they make these CO2 generators with a safety valve so that if the pilot flame goes out, the gas will shut off as well. This stops your room from becoming a gas-filled combustion risk.

CO2 Control

Controlling your CO2 amount is important because you don’t want to waste any of the gas, and therefore over-enrich your environment, do you? No, you do not, therefore the easiest way to regulate your CO2 in a CO2 tank is to buy, you guessed it, a CO2 regulator. It not only needs to be on a regulator though. The regulator needs to be attached to a timer that will be set according to the parameters you wish to set for it to be on and how much CO2 you want to be let out.

There are more automated controllers that actually detect the levels of CO2 in the room and release it when those levels are low. These will be more expensive, but may be worth it because it ensures your plants are getting the perfect amount of CO2. These automated controllers also may come with the function of controlling venting actions.
As you may have read from the above topic “CO2 Enrichment,” plants grow optimally in a room enriched with around 1000-2000 ppm of carbon dioxide, where anything over that will be toxic to your plants. This makes having the automation a stress free growing experience because you know, unless it breaks by rare occurrence, that your plants will be soaking in the rich air.

CO2 Enrichment, Temperature, and Humidity

Because plants give off moisture as a byproduct of photosynthesis, releasing about 97% of their water intake, it is important to have something to reduce the humidity of a room being supplemented with CO2. Carbon Dioxide, as you may recall, increases the plants “metabolism” and causes it to perform photosynthesis faster, with heat being a catalyst for that increase. This will vastly increase the humidity of your room and if not treated, will create an unsuitable environment for plants and will even promote mold growth. It will also require more heat, although lowering your heat will most likely be your main concern because running HID lights is always a big heat generator. There are a few products on the market that allow you to easily control humidity and heat problems like a 2 in 1 air conditioner, but you shouldn’t run into a problem if you have a portable air conditioner and a dehumidifier. Just make sure that your air conditioner doesn’t get too low because your plants like extra heat if they are being supplemented CO2. Heat is a universal catalyst for increasing reaction rates and this applies here as well.

All-in-one Controllers

Some controllers on the market have executive function over all of your environmental, and even sometimes nutrient and pH, needs and desires. They are simply set at certain thresholds that you want your room set at and perform at that level and no other. In certain setups you can even hook this controller up to a computer and control the settings from another computer over the internet.


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