Nico’s Nuggets: CO2, Ventilation & Controllers for Small Grow Ops

Hello, Nico! Can you talk a little about using CO2 in a tent, cabinet, or small grow where air/heat is also exhausted through a carbon filter? Is there a way to exhaust for heat, but still keep a good amount of CO2 in the garden? I spent the money on a nice carbon filter, a fan and a really nice CO2 setup. The area is 2 x4 x 7. Many thanks for your advice! – George T. via

Greetings, George and thanks for your question.

I always like questions like this that require some thought – and which can be solved using technology! The gadgets and tech gear that are in the marketplace today for us growers constantly impress me. From the home hobbyists to larger commercial growers, there exist garden solutions for nearly every scenario one might think of.

To start, it is smart to add CO2 to smaller gardens such as a tent or closet grow because a cannabis plant’s respiration rate is temperature dependent. For every 18 degrees (F) that temperature rises, a plant’s respiration doubles. This is especially important in tight indoor grow spaces where temperatures tend to be higher due to intense lighting and limited space. Adding C02 will greatly aid the plants respiration, and thus growth rate as the two are directly correlated, in these gardens.

Further, it becomes equally important to ventilate or exhaust heat build-up in small gardens to prevent the temperature from climbing too high. Optimal garden temps range from 68 to 75 F. Once garden temperatures reach the 80’s, rates of photosynthesis begin to rapidly slow. So how does one vent out the unwanted hot air while still retaining the precious CO2 added to the garden?

A larger CO2 burner with Smart Bee controllers over the garden.

Enter technology. Today, there are excellent control systems for all types of garden gear. Some controllers are all encompassing and can control lighting, ventilation, CO2, irrigation and nutrients, and HVAC systems all at once. From there, these controllers breakdown into much smaller control units from various combinations of controls to single-entity controllers. In this specific situation, we would want to utilize a specific combination CO2-exhaust fan controller.

You can find an easy-to-use CO2 controller that turns on your CO2 emitter when your garden PPM levels reach a certain point or when lights turn on (never use CO2 during the dark cycle) or when temperatures reach a certain set point. These controllers will also work in conjunction with your exhaust fans, ensuring that your ventilation system does not turn on during a CO2 infusion. Usually you can set these controllers to not exhaust garden air for a period of time after CO2 infusion. Your budget and the type of controller you purchase will determine what features are available as every controller unit varies.

A deluxe controller like this can handle several atmospheric controls.

The important aspects here to bear in mind are: Find a controller that has a light sensor so that CO2 is not emitted during the dark cycle; Make sure the CO2 sensor works by PPM (parts per million) levels; Be sure the controller has at least two plug inputs for exhaust fans – and that fans can be set to ventilate by both a set time after CO2 emission and by overall garden temperatures.

Thanks for reading everyone and remember: Grow… And help the world grow, too!

Got questions? Email ’em over to Nico at and be sure to put “Nico’s Nuggets” in the subject line!

Follow Nico on Social Media: @Nico_Escondido (Twitter) & @Nico_High_Times (Instagram)

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