What fans for my room?

Author: Scott  

Hi Scott

I have a grow room that is about 3m long 2m wide and about 2m high and I was looking at buying an exhaust fan for it. I would like something relatively quiet and I would like a filter Credit union to filter the smell as well. Could you recommend anything that you have in stock? Also I would probably need a fan to blow in fresh air as well.

Hi there.
3m x 2m x 2m is 12 cubic meters, or 12m3
Below 15 degrees, the plants have problems with growth as the solubility of phosphorus and other elements begins to drop .

Between 20 and 25 degrees is ideal
Above 30 degrees is a problem and you need to bring it down.
The important thing is to understand why we have fans.
1st to control heat (and humidity)
2nd to remove air and replace it with fresh air to provide enough carbon dioxide for the plants to grow.


If the room you described has two 600Watt lights in it for instance.
With one set of fans, these lights will add about 5 degrees to the room temperature.
If the air coming in is 5 degrees and the lights add another 5 degrees, then you probably want to have LESS fans so the room can come up to a nice temperature.

If the air coming in is 28 degrees and the lights are adding another 5 degrees, you need to INCREASE air changes. Doubling the airflow might only allow the lights to add 2-3 degrees to the room.

If the air coming in is 24 degrees during the day, then it should be fine, but at night, when it drops to 5 degrees you might put a timer on the exhaust fan (and the inlet fan as well if desired) to keep the warmer air from being removed too much.

Of course the humidity should be between 40 and 60% for these figures to work out.


We need 10 air changes per hour to provide enough Carbon Dioxide for the plants.
This is very important as this is the most important food a plant needs after light.
Everything else hinges on the plant getting light and air.
Then everything else can work.

I suggest 10 air changes per hour for a room until it gets to warm (120m3/hr)
A small inlet fan and exhaust fan will do. Continuous rated is recommended.
A $55 Lenco fan in and another out will do 400-600m3/hr. Fairly quiet because the opening is large, and the motor doesn’t have to run too fast.

We sell them as a bathroom style mount in the wall/ceiling or with a fitting to take 300mm ducting for $5 more.
A $130 150mm ducted fan would do about the same, but won’t be as quiet, sort of moderate noise, because the fan runs faster to pump the air though a small opening.

Once the air gets warm, using airconditioning is the ideal situation.
Otherwise, lots of air changes is required.

Maybe a $290 2000m3/hr fan like a industrial 4 pole ducted fan would work for your area if heat is an issue.

As for smell, Ozone is the easiest to manage. A $350 Ozone machine runs about 15mins per hour

I sell a few Carbon filters as well – starting at $290 for a 50cm tall stubby filter (see catalogue for info)

You need a centrifugal fan to make them work

They start at $290
This option can be more expensive.
If you want to go with the Carbon filters, I can work out the fans and filters to suit your room, but I’d prefer to know what lights you are running first.

Hope that helps.

Scott Andrew
Nerang Hydroponic Centre 4/50 Spencer Road Nerang QLD 4211 Australia Phone (07) 5527 4155
email checked morning and afternoon minimumon week days only


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