Often smelly and unsanitary
You should maintain high temperatures, between 85°F (30°C) and 95°F (35°C).
Please note: As you’re burning propane or natural gas to get CO2, this chemical reaction also adds water vapor into the air and increases your humidity. The increase in humidity is even greater when you generate a lot of CO2 or have a very small grow area. This extra humidity can become problematic in some cases, especially since you must seal your grow area to keep the CO2 inside. If you’re not carefully monitoring the humidity, you may put your plants at increased risk for mold (remember, humidity should always be below 70% in vegetative, and below 60% in flowering). A strong dehumidifier may be what you’re looking for in this scenario.
If you have a sealed room, then you will need to keep adding CO2 based on how much your plants are using. If the room is not sealed, you will need to replace CO2 at a rate equal to the amount plants use plus what’s being vented out. It’s recommended that you regularly test and monitor that CO2 levels are staying where you want them to be.
The pre-made systems like CO2 Boost are better, but they’re still expensive and don’t produce a whole lot of CO2
Note: It’s usually cheaper to get tanked CO2 from a welding supply store as opposed to a hydroponics store
No matter what, watch plants closely for signs of heat stress and react accordingly!
If you’re considering CO2 injection, ask yourself…
Even though CO2 levels in the air are much lower today at around 400 PPM, plants are still able to use CO2 levels at the higher concentrations, allowing them to produce more energy from the same amount of light. Growers can take advantage of this increased growth by providing extra CO2.
Will CO2 work for your space? How do you get set up? Learn everything you need to know about CO2 injection…
by Bobby Mercer
Controllers can be expensive, so many growers decide to go with the timer method. For these calculations you will need to know the volume of your grow room, as well as the desired level of CO2 supplementation. On my Plant Growth and CO2 page I walk you through all of these calculations step by step. For this example I will use your garden dimensions, and our goal will be to bring the room up to 1500 ppm CO2 (a fairly common level of supplementation).
Aluminum tanks are much lighter than steel tanks. 5 lb and 10 lb tanks will need to be re-filled very often, while 35 lb and 50 lb tanks are too heavy for most people to carry. For these reasons, I recommend a 20 lb aluminum tank for most indoor gardens. Having an extra tank (a backup) really comes in handy if you don’t want your garden to be without CO2 while you re-fill your only tank!
If you can get your room temperature to the point where there are appreciable spaces of time in between exhaust cycles, then here is how you set up your CO2.
In this example, if you set your flow control valve to .34 CFH, and programmed your timer to open the solenoid valve for one hour, you would slowly bring your grow room up to 1500 ppm CO2. This will only work if your exhaust fan does not kick on in the meantime to lower the room temperature. In reality, you should set your exhaust fan to kick on when the room reaches about 85 degrees, and to kick off when the garden reaches the ambient air temperature (hopefully about 65-75 degrees). Now, time how long it takes before the exhaust fan kicks on again.
Your flow rate and the amount of time you take to release it share an inversely proportional relationship. This means if you take 1/6th of the time to release your CO2, then you will need to multiply your flow rate by 6/1 (which is simply 6) in order to end up with the same level of CO2 supplementation you began with.
Bobby- your grow room is still running a few degrees on the warm side. If possible, I would try ventilating the grow light with it’s own exhaust fan, pulling air from somewhere outside the room, through the enclosed light fixture, and exhausting it somewhere outside the room. If you are running your exhaust fan constantly to keep the room cool, this makes it very difficult to increase the CO2 levels inside the room. The best solution for CO2 supplementation is to have your grow room air conditioned, and the grow light ventilated separate from the rest of the room.
5 minutes is actually 1/12th of an hour. In order to release the necessary amount of CO2 in this time, you need to multiply the original flow rate in this example (.34) by 12. This gives you a flow rate of 4.08 CFH. Now you can set the flow control valve on your tank to 4.08 CFH, and set your timer to open the solenoid for 5 minutes immediately following the end of each exhaust cycle. The trick here is coordinating your exhaust fan with your CO2.
Your garden is 7 x 5 x 8, which equals 280 cubic feet (the volume of your garden). CO2 levels in the atmosphere are normally around 300 ppm, and our goal is to bring the grow room up to 1500 ppm. Therefore, we need to increase the CO2 levels by 1200 ppm (or .0012). We calculate the amount of CO2 we need to release into the garden area by multiplying the increase (.0012) by the garden volume (280). In this example, we will need to release .336 cubic feet (CF) of CO2 to reach our goal of 1500 ppm. For convenience, I am rounding this number up to .34 CF.
How to set up CO2 in your grow room. Step by step instructions on how to get the CO2 levels just right