CO2 and Flushing Air

by James

In regards to CO2 enrichment; If the temperature and humidity is completely controlled in your grow environment and appropriate CO2 levels are maintained with pure CO2 out of tanks, is there any need to flush the room with fresh air throughout the "lights on" period, apart from when the night cycle is activated?

I understand that if using a gas burner to enrich the environment, you would want to flush the air as you have more heat, humidity and other emissions (such as carbon monoxide) that you wouldn't want accumulating, but I can't see why else you would need to do it??? It seems everything I have read about this, people are replacing the air in their rooms intermittently only to correct temps and humidity! Maybe I'm missing something completely!

Answer: James- your intuition is spot on in this case. There are only three reasons to run an exhaust cycle in a grow room. To lower temperature, to lower humidity, or to replenish falling CO2 levels. Most indoor gardeners cannot afford to air condition their grow rooms or add CO2 from a sophisticated CO2 system....and so most grow rooms you read about rely heavily on exhaust fans.

The type of grow room you are referring to is called a closed system, because there is no need for it to interact with the environment outside the grow room. In a closed system, an air conditioner is used to lower the temperature whenever needed. This usually is enough to lower the humidity to an acceptable level, however, a dehumidifier is also kept in place just in case. To combat falling CO2 levels in the room, compressed tanks of CO2 (along with regulators and a release mechanism) are usually used in lieu of a natural gas CO2 generator to help eliminate any unnecessary heat sources.

A room such as this can run indefinitely without the need for an exhaust fan or a fresh air intake. Of course, oscillating fans would still be very important for air circulation inside the grow room and should not be confused with "exhaust" fans, which perform a very different function. The thought of Carbon Monoxide had never crossed my mind, but it would probably be a very good idea to mount a Carbon Monoxide detector in or just outside your grow room if you decide to use a natural gas type CO2 generator.

Thanks for the enlightening question James, and Happy Growing!

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Apr 10, 2010
Combustion of Carbon-based fuels
by: Kevin

My understanding of the burning or combustion of paraffin, yields no Carbon Monoxide - here is the equation:
C25H52 & 39 O2 --> 25 CO2 & 28 H2O
which means 39 molecules of Oxygen combines with so much paraffin to release 25 molecules of Carbon Dioxide (CO2) and 28 molecules of Water (H2O) - there is no Carbon Monoxide.

However, incomplete burning can and does occur, which can result in Carbon Monoxide of varying levels. (Which have sadly led to some deaths, as publicised in the media.)

I consider a Carbon Monoxide sensor alarm to be an essential part of any indoor living space including where grow rooms are situated. As it costs only pocket-money to buy there really is no reason not to have one. In a closed grow situation then an alarm is necessary inside the grow area.

However, CO2 monitors are very expensive and one needs to be careful not to overdo the CO2 levels, although if you get an infestation of bugs, very high levels of CO2 short term (like an hour) will suffocate the bugs and kill them.

An early warning sign for we humans are dizziness and tiredness when we are exposed to high levels of CO2 and we feel better when we leave the area.

When Carbon Monoxide (CO) is taken in by humans, the red blood cells absorb CO2 much more easily than O2 and displaces O2 *permanently*. That red blood cell cannot accept O2 ever again. The only way to get over CO poisoning is a blood transfusion. That is why people become tired when exposed to CO.

There's pretty much no need for CO2 for everyday growers as replacing the air frequently will give your plants all the CO2 they need. I refresh my air twice a minute - yes, twice a minute! And it's cheaper and safer and easier - but quite a bit noisier!

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