Thread: Fans On or Off during Lights Out??

I have not been running my fans during "lights out" and I am growing in a closet where the only airflow is provided by fans. The only air that comes in is through the duct work during that time. Is this ok? I'm not like suffocating my plants for 6 hours or anything right??

I'm trying to figure out what happened to my seedlings and just trying cover all the bases.

Well Doco,

Why don't you run them 24hours and find out. So you think that 6 hours without fresh oxygen is okay? Hmmmm maybe plants are just a little different from people. Not too many thing survive without oxygen. If your seedlings were outside they have all the fresh air required.

Loco

Loco, a fan does not create oxygen. It just blows it around. You need to spend a little more for that feature.

Loco, I didn't realize that he was bringing fresh air in. My fault

I think to know for sure, you would have to take a reading and find out how much Co2 is inside when the lights are off. Maybe they are breathing ok if the temps good.

ok, but do you run your fans during dark periods in your grow room or cabinet?

doco, i run my exhaust 24 hrs. The fan to cool my light only runs when the light is on

the fan is good for 24-hour use, it strengthens the stems, and helps prevent mildew and molds ... good air circulation is vital ...

Originally Posted by locomark

Well Doco,

Why don't you run them 24hours and find out. So you think that 6 hours without fresh oxygen is okay? Hmmmm maybe plants are just a little different from people. Not too many thing survive without oxygen.

Loco

I also wasn't sure if i needed my vent fans on when lights are off.

When you turn the fans off there is a lot of O2 in the room, actually 21%. I can understand that CO2 would be depleted quickly if there wasn't ventilation because there is only a 0.035% concentration of CO2 in the atmosphere. so thats 600 times more oxygen. it wouldn't surprise me if the plants didn't use all that up in only 6 hours. other wise that means that the CO2 in a room would be used up in less than 0.6 min.

does anyone know...

If you guys are saying that the plants need lots of O2 then your wrong(they need Co2), but if your not sayin that then your right.

I believe plants dont use Co2 at night. It is only beneficial when a lot of light is being used and temperatures are high. That's what I read somewhere anyway in more that one piece of literature - but I could be wrong. Any one know difinitively.

TGT

I have my regular fan off right now for the current 12hr dark period with no holes in the room. I'm sure the room is not air tight though. If you have fan holes that allow air into your room and your plants are not showing signs of suffering, I think you're probably ok. One would think that the plant needs air even when the lights are off since the plant is alive. Actually, I've noticed alot of growth after the dark period, so the plants are still alive and growing in the dark.

I didn't drill any holes to install intake/exhaust fans because I didn't want to bring cold air into the room and then have to turn on the heater to bring it back up. I have been experimenting with the regular fan off since the temps are already down during the dark period. So far so good. But my plants are not in a box, they are in a room. I already bought the inline fans and the flexible tubing, but I'm trying to get away without making the holes. Like I said, I think the only way you will know for sure is by trying it, or by taking a reading to make sure that the plants have air to breathe during the dark in your box. My plants have been in a room without any holes during the dark period for about a week now. I open the door for fresh air when the light is on.

I am curious about this as well. I have a six inch vortex that blows my air through a carbon filter. My night time temps are super low and I just bought a space heater. Obviously having the room flushed of its air all the time is a bit counter productive to trying to heat the damn thing! I am considering turning the fan off for 10 mins every half hour so the heat will be used more effeciently. Or would it be better to do 20 mins off-->40 mins on type thing?

Exhaust should run 24/7 (if not running co2) for the following reason:

Cool air holds less moisture than warm air so when the lights go off the moisture will condense and cause dew, especially right after watering. Dew covering your walls and windows and equipment is generally not good but is especially bad for big flowering buds for obvious reasons.

Running your exhaust at night constantly vents the humid air out of the room.