Venting- BLOW OR SUCK?

I always thought it was appropriate to suck your air through your hoods. Now come to find out they say to "blow" the air. Apparently this is to increase the longevity of your fan.

Thoughts?

you get a more powerful vacuum by pulling air through and a weaker one trying to push past obstacles and through...

but...

by pushing you get 'positive' pressure so no smells will bypass your filter because of positive pressure pushing already scrubbed air through any cracks or openings before its intended exhaust point.

If you are pulling air that you want scrubbed there is a chance you will pull unintended air in through seams and cracks that occur after the filter and you will have smells at your exhaust point.

if your not using a filter (I personally suggest to) suck the air through.

My dilemma is that I will be running CO2. So somehow I have to circulate air through the hoods without disrupting the air flow in the room. I have a separate inline fan with a carbon filter. That second fan will be separate from the hoods. My thinking is that the room will already be constantly filtered, so any air that escapes into the hood venting will already be clean. I could take extra precautions and try to seal the hoods up best I can. However I am sure air will still get in somehow.

Dedicate a fan for just your lights.....intake from outside-through lights- back outside. Get a good seal on your ducting.

Blue painters tape on hoods to seal them. Never blow air INTO a carbon filter, always always always pull it in through the carbon (and use a prefilled)

Always use a pre filter.

Blowing air into and taking off the filter will rapidly coat your carbon in dust. Translayiin, your filter doesn't work anymore

Morbid Angel said:

you get a more powerful vacuum by pulling air through and a weaker one trying to push past obstacles and through...

but...

by pushing you get 'positive' pressure so no smells will bypass your filter because of positive pressure pushing already scrubbed air through any cracks or openings before its intended exhaust point.

If you are pulling air that you want scrubbed there is a chance you will pull unintended air in through seams and cracks that occur after the filter and you will have smells at your exhaust point.

if your not using a filter (I personally suggest to) suck the air through.

Click to expand...

I'm pretty sure you want negative pressure and not positive and pretty much for the reasons you said but opposite. Idk y pulling air through seams and cracks would be an issue when it's just going to be getting pulled through your filter.

I would think having air pushing through those same cracks and seams would increase your chances of unfiltered air escaping your tent. I could be wrong tho that's just been my personal experience.

thegreensurfer said:

Dedicate a fan for just your lights.....intake from outside-through lights- back outside. Get a good seal on your ducting.

Click to expand...

^^

now, @mrgreen2015 'would you rather' add or subtract a variable and minute amount of outside air into your c02 dialled room.

I have tried both ways above and a fan between lights. My fav was fan between lights in my setup. As stated above when I blew air not only did my lights move from the network expanding it also build a positive pressure in my room from the small leaks in the duct work. My room was attached to my house of course so the pressures would creep into the house and smell the whole house. When I suck the air I did not have this issue but felt like air was being removed from room and I was using a fuck ton of propane for c02 burner to keep ppm levels. 'I then place the fan between each light and I think that was the best as I did not use much propane I didn't have smells in the house or outside of the house. propane went down phenomenally I used 2 tanks per grow Instead of 3.

Morbid Angel said:

^^

now, @mrgreen2015 'would you rather' add or subtract a variable and minute amount of outside air into your c02 dialled room.

Click to expand...

Not sure. I have 2 in line fans though and running CO2. So I'm guessing suck the air out of the hoods using air from an outside room on one side and back out to another room on the other. Then use my 2nd fan to hook up to the filter. And keep the filtered air in the room and redistribute the CO2. Sound ok?

It depends on how many lights your running, fan size and the time of the year ( high temps)

if your running a 6" fan and its summer and pulling 30c air through 3 hoods and then it goes through the fan its going to get really hot and could be a fire risk so you should push the air but IMO push air will reduce the air flow a little so the grow room will be a little warmer
(this is based on you having a good ac unit, air cooled hoods will reduce some heat and reduce the ac running cost as there very expensiveto run )

If you only running a single hood in the winter and want maxuim air flow you need to pull the air through the hood, ( so you can get the hood a few inches closer to the top of the canopy)
the low heat from the hood will not afect the fan and fans are built to pull air not push it, so the fan should last longer

You want negative pressure if smell is an issue...I'm an HVAC service tech so this is a common issue for many businesses. And as mentioned before pull air through carbon filters

I am in agreement pulling three rather than pushing I would consider getting a higher cfm fan I would use a adapted eight inch fan to pull three bouth light and use your 6 inch to run your filter