Humidity/Smell vs. Exhaust fan issue?

[CharlieWaffles]

I’m not sure if I am doing something wrong or if most just live with this.

I grow in a 4x4 tent in my heated shed. My 6” Vivosun exhaust fan with charcoal filter vents directly outside. I also have fresh air coming in from outside through a different vent. And fans for circulation. All good. The problem for me is that in order to keep the smell in my shed at bay I have to run the 6” exhaust fan 24/7. When the plants are seedlings I don’t have to but once they hit 6-7 weeks the smell is overwhelming if I turn off the exhaust fan. And that’s not even during the flowering stage! Of course having the fan running all the time eliminates most of that smell but it also takes out all of the needed humidity even with a large humidifier that I have in my tent. And the exhaust fan is so loud even on the lowest setting, at least to me it’s too loud. Apparently it’s a quiet one and only runs at about 29 dB I believe I’ve read. I don’t know how people would live with this noise in their actual house! Or the smell. So how do I keep the fan running 24/7 and keep the proper humidity in the tent? I’m considering getting a 4” exhaust fan instead as I find a 6” is too powerful for a 4 x 4 tent anyway. But I would love to know other people thoughts and opinions on this? Have you ever run into the same? Any help would be appreciated.

 

[SmokingWings]

My 6” Vivosun exhaust fan vents directly outside

Do you have a charcoal filter in the set-up? If you do then you could pull air from the tent and have it go through the filter and then vent it back into the tent. It should then keep the humidity about where you want it without having to use a humidifier.

I also have fresh air coming in from outside through a different vent.

Or vent the exhaust into the shed itself and have the incoming air come from the shed which again would help keep the humidity in the tent where you want it.

You did not mention a charcoal filter which would help eliminate the smell from the air. That is why you could vent the air, which is still close to the humidity you want, back into the tent. Or vent into and then draw from the shed. It should help reduce the costs involved in constantly running the humidifier.

In the long run it is easier to maintain the environment in the tent by using the shed as what is sometimes called a "lung room". Maintain the lung as far as temperatures and humidity and the tent will be right behind more often than not.

 

[CharlieWaffles]

Thanks for the reply. I edited the original post to add that charcoal filter. My filter is currently in the tent attached to the exhaust fan which then pipes the air out of the tent through an exhaust port directly outside. The humidity in the shed is no where near what I want it to be in the tent. My shed is typically 30-40% RH humidity from September to June. I definitely don’t want to vent into the shed as it would certainly smell even more, which is what I’m trying to get away from. Everything is fine until I turn off the exhaust fan. Then the smell becomes ridiculous. Also I find if I keep the tent closed up tight the smell in the shed is better, but with the exhaust fan running and no vents open in the tent my tent walls compress a ridiculous amount and the walls suck in and push on the plants. Certainly not ideal
I must be missing a step or something.

 

[Roy Growin]

Why would venting scrubbed air into the shed and recirculating make the shed smell?

 

[Keffka]

I know @StoneOtter has a muffler he uses for his blower, perhaps he has some input

 

[CharlieWaffles]

Why would venting scrubbed air into the shed and recirculating make the shed smell?

Good point. I missed that about it already being scrubbed. So I wonder why if I stand by the air vent being exhausted outside I can still smell it?

 

[Roy Growin]

Good point. I missed that about it already being scrubbed. So I wonder why if I stand by the air vent being exhausted outside I can still smell it?

When did you last replace the filter? The vent out shouldn't smell at all

Just to be clear, your airflow is: intake [from outside] to tent > filter [in the tent] > fan > vented outside, right?
They may as well be outside, that's the problem

 

[CharlieWaffles]

When did you last replace the filter? The vent out shouldn't smell at all

Just to be clear, your airflow is: intake [from outside] to tent > filter [in the tent] > fan > vented outside, right?
They may as well be outside, that's the problem

Yes that’s correct on the airflow. Filter was replaced about 8 months ago. I usually replace it yearly.

 

[Roy Growin]

My tent is in a small room, airflow is: room air>passive vent>tent>fan>filter>room and there is no smell unless I open the tent up - you should be able to do that in your shed

 

[CharlieWaffles]

My tent is in a small room, airflow is: room air>passive vent>tent>fan>filter>room and there is no smell unless I open the tent up - you should be able to do that in your shed

Exhaust fan on 24/7 ?

 

[Roy Growin]

Exhaust fan on 24/7 ?

Only in full flower and the first few days of drying
If you are thinking of the noise, I use a variable speed RVK and you'd have to stand right next to it to hear it

 

[SmokingWings]

So I wonder why if I stand by the air vent being exhausted outside I can still smell it?

The fan is not moving all the air through the filter so most of it is still in the tent picking up odor from the plant. The filter is not able to capture the molecules of odor before the pressure from the fan pushes the air out the shed. In the meantime the air in the tent is picking up more odor.

If the air was being vented back into the tent the filter would be continuously pulling smell from the air so it become less and less noticeable.

All in all it does not surprise me that some smell still remains when you are standing by the outdoor vent.

 

[CharlieWaffles]

Only in full flower and the first few days of drying
If you are thinking of the noise, I use a variable speed RVK and you'd have to stand right next to it to hear it

This got me thinking. I have another separate speed controller; would it be possible to run 2 speed controllers and get the fan turned down even more? And voila! I’ve dialled it in to get the fan to an appropriate level where it doesn’t suck the tent in so much that I loose space inside and the noise level is a lot better. And I don’t think I’ve turned it down so much that it could possibly cause an issue with the fan motor. Just a few decibels makes a huge difference. thanks for the idea !
First problem solved.
I’ve ordered a new charcoal carbon filter. Maybe this one just wore out faster than previous ones they just wasn’t scrubbing the smell anymore.. We shall know in a week or so

 

[CharlieWaffles]

This got me thinking. I have another separate speed controller; would it be possible to run 2 speed controllers and get the fan turned down even more? And voila! I’ve dialled it in to get the fan to an appropriate level where it doesn’t suck the tent in so much that I loose space inside and the noise level is a lot better. And I don’t think I’ve turned it down so much that it could possibly cause an issue with the fan motor. Just a few decibels makes a huge difference. thanks for the idea !
First problem solved.
I’ve ordered a new charcoal carbon filter. Maybe this one just wore out faster than previous ones they just wasn’t scrubbing the smell anymore.. We shall know in a week or so

Because the exhaust fan is running 24 seven now to help with the smell, I can’t get the humidity to stay consistently above 30%. My humidifier is running 24/7 and it doesn’t even seem to be making it dent.

 

[Roy Growin]

Damn - tricky environment for sure
I don't really see why humidity is not building, only thing I can think of is to turn off the fan 1am-5am when there's nobody about, maybe that would help?
Is it always that dry in your locality or is it just low atm?

 

[CharlieWaffles]

Damn - tricky environment for sure
I don't really see why humidity is not building, only thing I can think of is to turn off the fan 1am-5am when there's nobody about, maybe that would help?
Is it always that dry in your locality or is it just low atm?

Hey Roy. Thanks for your help.
For me I think it’s not building up humidity because the exhaust fan is continuously sucking it out. I used to run my exhaust fan on a schedule; off for 1/2 hour on for 15 mins etc. tried numerous time configurations but whenever the fan is off, the shed stinks. I don’t mind the smell but I don’t want it on everything that is stored in my shed, or on my family. And when people come over and walk in the shed they comment right away on the smell if the fan is not running 24/7.
Humidity is an issue from October through end of May. June, July and Aug are just fine lol, a whole 3 months where I can easily dial it in. Maybe I need a more powerful humidifier but I see people using a lot smaller ones than I use with no issues. Pic of the one I’m using is attached. I still grow decent weed but I’m always wondering if I’m missing out because it’s never in the ideal window people talk about and maybe it’s why I get “airier” buds sometimes.

 

[bluter]

Why would venting scrubbed air into the shed and recirculating make the shed smell?

it will build no matter what. mostly because it isn't just moving air but water as well. if you vent indoor it's only a matter of time until the vapour and odour penetrates soft materials deep enough to be permanent.

90% of growers are nose blind to their own space and never know until it's a reek lol.

This got me thinking. I have another separate speed controller; would it be possible to run 2 speed controllers and get the fan turned down even more? And voila! I’ve dialled it in to get the fan to an appropriate level where it doesn’t suck the tent in so much that I loose space inside and the noise level is a lot better. And I don’t think I’ve turned it down so much that it could possibly cause an issue with the fan motor. Just a few decibels makes a huge difference. thanks for the idea !
First problem solved.

yes. you can control the exhaust to effect the rh. a lot of programmable exhaust fans work this way. you can also add a damper which is an old school mechanical way of controlling exhaust air flow.

I’ve ordered a new charcoal carbon filter. Maybe this one just wore out faster than previous ones they just wasn’t scrubbing the smell anymore.. We shall know in a week or so

new filters go a long way.

Because the exhaust fan is running 24 seven now to help with the smell, I can’t get the humidity to stay consistently above 30%. My humidifier is running 24/7 and it doesn’t even seem to be making it dent.

i grow through very low rh. i would prioritize air movement over rh every time.
if you can, exhaust to outdoor, use a fresh scrubber, and try rh control for the fan. the combination will likely dial you in.

if you are exhausting to outdoor and the odour is still excessive, ditch the rh control, and run the fan at the level you find the odour dissipates. then have a look where the rh is and how the plants are, if it needs further tweaking. revisit it then.