Viper:

If your talking about the CO2 boost - it goes on only during the light cycle.
Mr. GreenJeans 800 Reviewed by Mr. GreenJeans 800 on . CO2 BOOST ADVICE Hey everyone: Got one of those CO2 boost units on Friday and it was easy enough to set up. So here's my question open for discussion..... My garden I can usually run at a comfortable 79-81 degress with proper ventilation - humidity about 42% and everything is going great (touch wood) on flower day 21. Problem is the CO2 boost says for optimal use to make sure the room is sealed, which as everyone knows itn't really practical. I called the company that makes the unit and they said Rating: 5