E-mail - Ventilation and CO2 Use

Hello. I have answered the first questions about CO2 and plant growth, I had to ask Perry a manager at HTGSupply for the question about the ducting etc. He is much more knowledgable than me about equipment use. His answer is below mine in purple.

Dr. Myers,
Upon reading your article, "Information on CO2 Ventilation for the Growing Season," several answers of mine were answered; however, some of questions remained unanswered.
First- You were clear on the amount of CO2 to release, but I would also like to know:
1. How often should I release it if I have no meter (5 min/hr)?
If you see Perry's comment below, you would be wise to invest in a meter. You will end up using more CO2 if you do not, which means the meter will pay for itself in CO2 savings. This really is the only solution. If you don't know how much CO2 is in the grow area, and how much is being released (time/hr is not going to give you these numbers) no one will be able to tell you if you have enough CO2. You could start out at 5min / hr until you get a meter.
2. At what point during the grow cycles are critical?
a)Is it optimal to provide CO2 from seedling to harvest?

Great question!  CO2 is needed for photosynthesis and studies have shown that when the CO2 rate goes up so does photosynthesis. So, I think you'd have the best results by providing CO2 to your plants from seedling to harvest.

Second: I now have a question about ventilation:
1. With the provided 4" ports on the HTG small grow tent; how should I configure, and what parts are needed for proper ventilation? I will have the 4" carbon filter/fan combo, but that is it. Also, My reflector wing does not have ports of any sort. (socket on one end and open on the other)

If you are utilizing a CO2 injector, then it will be best to use the fan and filter combo as a means to cool the lamp, whilst minimizing the exchange of air inside the tent! This means that you will need a Air Cooled reflector! This is a reflector that has a housing surrounding the lamp with a piece of glass underneath and flanges on both ends to connect ducting/fans , thus making heat removal possible. Or a glass Cooltube type reflector.
The Reflector you described sounds like a standard Lightwing or Waxwing reflector, also called a Batwing, which is not air coolable.
Fan and Filter will need to be "run through" the tent and consequently through the reflector at the same time. A total of 4 flanges will be needed, two per port sandwiching the tent material between to create a double flanged port on both sides. This allows you to connect the air coolable reflector to ducting and the flanges on the inside, while at the same time providing a mountable surface on the outer side to attach ducting to the fan and filter. Essentially the filter will be on one side of the tent, connected to the tent with ducting, then ducted to the reflector, then to the other flange, then finally back out to the fan. This completely segregates the air going threw all this from the tent! Complete heat removal, without affecting the CO2 levels inside the tent!
The Fan and Filter Combos can be used to cool the tent. However this will affect CO2 levels and I strongly recommend using a control unit! Essentially the filter is hung from the tent framework from the top. The ducting then runs to the fan which pulls air from the tent via the filter and exhausts it to a outside(of tent) area. This will clear the tent of CO2 within a minute or two!
Operating a CO2 injection system without a Controller unit is hard! Plus may end up costing more in the long run. Do a google search for "Using a CO2 injection system without a Controller". There are many "hands on" responses from a variety of forums! All mention that typically using a controller will reduce the need to replace CO2 tanks by half. So a tank that will last you 2 weeks controlling it with a timer will last 4 weeks if controlled by an actual CO level controller. Within a short amount of time, replacing spent tanks will cost you more than a control unit does!
Thanks and have a great day!

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