Why use it at all? You do have humans living there with you, dont you? Thats all the O2 that you would need. I have heard many claims that by adding O2 to your grow system that the plants will really florish. Not so. I found that one out the hard way. When I ordered my grow cabinet it came with the adapter to add the CO2. I did that. But then when I got down to it, turning off lights, pumps, etc. it became a real pain in the ass. I called tech support of the people I bought it from and what they told me is that it is just not worth the effort to use. If you have humans in your home or dogs and cats or whatever, or can just open a window once in a while, it just makes little or no difference.