Indoor Air Circulation

Hi Nico,
Quick question: If I am growing a half dozen plants in a small shed connected to my garage, can I bring in air from inside the garage rather than outside for CO2 purposes? Thanks in advance. – Brad H.

Greetings, Brad! And thanks for writing in to us.

I like this question because the answer is multi-faceted and touches upon a few key indoor cultivation principals. First off, your primary question centers upon air exchanges and circulation within your garden – a good concept for all indoor growers to think about. All too often indoor gardens suffer because of the lack of proper air exchange and circulation. Many growers tend to conveniently overlook this aspect of an indoor garden, preferring instead to focus on their garden security and keeping their growrooms sealed as well as they can. I can’t say I blame people for wanting to keep their gardens (and themselves) secure, but this does not help your plants and, in extreme conditions, will likely harm them.

Indoor growers need to remember that plants have evolved outside in nature for millions of years and bringing them indoors these past 40 years to cultivate is still relatively unnatural for them. Bringing fresh air into the garden space helps prevent molds and bacteria from forming in stagnant air and water. It also helps larger growrooms stabilize humidity and temperature by preventing heat pockets from forming under intense lighting.

However, the downside is that if the intake air is not properly filtered, growers may also be introducing the new bacteria strains or mold spores into their gardens. It can be quite the paradox. This is why it is always best to use filters on both your intake and exhaust ports within your garden. Activated charcoal filters will scrub the air well, and if you can add the UV light option to your system, this will help ensure no pathogens make it into the garden. Also, remember to bring cool, fresh air in at the floor and to exhaust hotter air from near the ceiling.

In terms of using your garage air to help boost your CO2 levels in your garden, this is a good idea in theory, but in reality the PPM of regular indoor air versus outdoor air is going to be negligible (400-500 PPM indoor vs. 300-400 PPM in ambient outdoor urban air). And running your automobile engine will produce much more carbon monoxide than carbon dioxide, not too mention is extremely dangerous, and thus NOT advisable at all.

For a small garden, I recommend looking at the CO2 Boost buckets which are very inexpensive and can bump CO2 in small gardens up a few hundred PPM. They are all organic, as well and an excellent option for home growers. Barring that, a small CO2 tank and timed regulator would also work, but this option is more expensive to get set-up and not always worth it for small home gardens.

Remember also that using CO2 in gardens that are well ventilated requires added attention to your atmospheric controls. Growers need to make sure that when their exhaust fans go on their CO2 systems shut down temporarily, so as not to exhaust the valuable CO2. Commercial controllers and timers are available in the market to make this type of programming and timing very simple. Here is an example of such a timer.

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!
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