new 12x12 room air tight Co2 need help

Hi everyone I am new here and new at growing , but not to gardening. I was wondering if any of you could shed some light on my fresh air venting in this grow room I built. 12x12 well insulated and air tight. I read different opinions , some say co2 does not need fresh air ( doesn't sound right ) to how much Co2 can we waste to exchange air. running 2-600 watt hps/mh vented hoods with outside air through hoods and out of room. geenair CD3 generator, PPM telaire co2 controller, 50 pint dehumidifier, 2 wall mounted fans, and 2 floor fans to keep air moving, 8" carbon filter fan at ceiling height vented out of the room , 6" fresh air vent with inline fan and self closing damper to slow air movement when not in use. turning these 2 fans on at same time will exchange the air in the room in about 1.6 munites . What I cant find out is can I run my 18 hr light cycle with no air exchange and hit the fans and turn off the co2 during 6 hr night cycle period to give enough fresh air to my plants each cycle, I' m not clear on how to time the fresh air exchange. any advice would be a big help !!!thanks 16plants

Never ran sealed but always been interested,and as you already said,ventilation when using c02 isn't necessary.All cooling is handled by an a/c,preferably a ductless minisplit.c02 is supplied by tanks,generator,or burner.IMO,if there's ventilation,it ain't sealed as sealed means SEALED.

I know I will have some bugs to work out , but....0......fresh air Hmmmmm , I did a test on the room set the co2 to shut off at 1500 ppm which it did then I left the pilot light on over night and the room was 3235 ppm in the morning. I don't know the numbers on what each plant uses when lights are on , I know none when there sleeping. Seems I need to get some of that co2 out of the room during the sleep cycle or not worry about it.

The reason you're seeing such high ppm of c02 during lights off is due to the fact that yhey use most/all c02 during lights on from my understanding.If running c02 during lights off,that is unnecessary as plants give off c02 mainly at night.

Don't take my word for it though as I've never used c02.

yes your right they dont use CO2 at night so u need to get your out take an in take fans on during dark hours or your humidity is going to go throu the roof during the flowering stage

Turn it off at night.

CO2 is used most in the morning/lights on. If you have timers and heat isn't an issue you can shut down ventilation and run CO2. Just keep a fan on the floor blowing up ad CO2 is heavy and will want to settle to the floor. Let it roll around in there a bit then kick exhaust on. Should save some CO2 from being wasted.

Hey thanks for all the reply's and input, as a point of interest I have no plants in the room yet so there is no Co2 being used sorry should have mentioned that , trying to get the room tuned in before My baby girls go in there !!! that's why I was concerned with the Co2 gen. Cant shut off the pilot light then it wont come on automatic when the levels drop, I have the range set for 1300 to 1500 ppm. But I can put the Co2 controller on the lights out timer so it would not kick on and waste propane during the venting sleep cycle, that would work. that way the pilot light will remain on. My other worry is the heat build up , my test run with 3- 600 watts running full bore , Co2 going , 3- fans moving air I had a temp that seemed to hold at 84 degree's but my humidity was at almost 80% .......... my dehumidifier should be here any day !! I hope the need for a split AC unit isn't necessary .. I look into one ......$$ ouch ! So thanks to all your input I will do no fresh are venting during the light cycle and maintain 1500 ppm's co2, keep the temp around 85 degree's I hope, set my dehumidifier at 60 % . Then run my venting during sleep cycle that pulls fresh air in to the room and exit's by 8 " charcoal filter. that will also lower my temps at bit during sleep time more than 10 degree's so a backup heater set at 75 might be a good idea. Give you update soon as I get a few days on my girls in the new room !! thanks 16p

Co2 is fresh air for your plants. You do not need to exhaust at all, ever, period.

Ok thank you very much mjjabel for that very to the point advice. I have read what you are saying and seen video's of a wonderful garden done this way. I have some things about this air tight room and my set up that gives me cause for concern. Like the pilot light on (with no plants in the room) ran the ppm over 3200 in 10 hrs so are you saying no worry about that ? at that rate even with the plants in the room I would be over the 1500 ppm recommended with just a pilot light on my co2 gen. that I don't want to have to shut off and relight every day multipal times. So I have some bugs to work out as you can see and don't forget I am new at this and I do thank you for all input for sure. It seems reasonable if this runs true with a high ppm in operation to remove a little air during sleep time , no harm done the pilot light will be burning anyway to pickup what gets exhausted . I called and talked to the manufacture of green air Co2 , he said that model would run 3 months on a 5 gal tank of propane. Just saying , at this point not worried about a little lost co2. but so far this is all talk and theory for me. Let me get this up and running and Id be glad to report back how it's working ................or not !!

Also depends on where u live an the climate but i think u need Mini Split air con even with cooled hoods. The Air Con will also help to dehumidify the room so does two things so worth it.

Small plants dont need 1500PPM of CO2 either start of low an build up.

Is this your first grow?

As if it is id lose the CO2 as u havent got complete control over everything in your room yet once u have that control then bring CO2 in, If u have experience, Still do one grow without to get the room dialled in.

then on your 2nd grow, grow same strain so u understand that style plant an u will get amazing results.

Yes this is my first grow , thank you machead for the sound advice , as well as everyone else your all very helpful. ya I think I will need a split air to be safe, I didn't find the info on the split air till after I ordered a dehumidifier should be here in a couple days. my budget for this room was 2000 I am there +some !! wish I would have known I would have not got the dehumidifier and bit the bullet for the split air..... grrrrr! I tried to read all I could on forums and the grow bible by Cervantes...... I do live in the north west on the ocean pretty moderate climate was hopping to avoid the split air. Your advice Is good I should bunch the Co2 this first grow get the room dialed in. But I do have a plan to try......I know newbe dip shit !! #1 See if I can keep my temps at 85- 90 degree's is what I'm reading for co2 , running with 1- 6oo watt light on 15plants (my legal grow limit I do have 2 lights set up if needed) ,co2 during light cycle, exchange air once every hr during a 4 hr sleep cycle, run dehumidifier 24/7 at 60 %. my fan set up will exchange air in under 2 minutes. plan #2 If that doesn't work I'll just use my in/out venting system on a timer to keep fresh air in the room, can the Co2 for now and do a normal grow then save for a split air . thanks man !!