OK, i'm running 2 125w and one 200w envirolite, wich ive sealed in the top of my small growbox with perspex.
2 120mm pc fans run out of this section, acting like cooltube

my grow space is about .25m x .25m x .45m = .028m^2
an air change every 3 mins means 0.6m^3/min

Im using pc fans to do this, keeping temps in the low to mid 20s, so no problems... except the smell

Iv got 2 sheets of cooker hood carbon mat over the all openings, but im now 2 weeks of chopping 2 lowryders, and im getting grief from housmates about the smell, and iv got another 6 starting flowering

I cant use proper cabon filters, becuase the pc fans won't pull thru them, but i cant pull thru with proper fans, one because of the space, and 2 because the fans needed will pull 160m^3, far too much

I think my box is leaking (like a sieve) which doesnt help, so i'm going to rebuild anyway, so I was hoping someone else has done something similar and came up with a decent small filter

So thats it then, any ideas?????

I use an EBM papst fan from RS, it generates a lot of pressure, enough to blow through a DIY carbon filter.

The downside is, it also generates A LOT of noise. I've boxed it up in a DIY acoustic enclosure and run it at 3/4 speed, but it is still pretty noisy. Probably equivalent to the noise of a computer in the room with you. Without the enclosure and run at full speed, it sounds like a hurricane.

the part number in rs (www.rswww.com) is 250-965 and it is a beast of a fan. Runs off 12V DC so can be run off a decent sized power adapter (i use one with a variable voltage output from maplins).

I looked into this pretty extensively and this fan was one of very few, that generated enough pressure to blow through a filter and maintain enough flow for decent cooling.

cheers, i'll look into it

also ive thought of using a gas mask filter, if it can filter mustard gas, a few plants should be no trouble right? theyre fairly available in surplus shops and fleabay. has anyone else ever tried it?

ive just brought some of that pet shop stuff still need to fit it so il get back to you on that but i never even thought about a gas mask, good idea mate
N.P

In your situation it sounds as if it will always be somewhat of a trade off between noise and getting the airflow right through the filter and keeping the temps in your space good.

I would have thought a gas mask be too small for the application, but worth a go.

You can always site the extractor and filter outside of your space - extract from your space with duct and 'blow' in to the filter. This is not ideal, but does work.

Look about and see what fans you can find....I would maybe start here and then look at adapting one of the DIY carbon filters to suit the fan.

Good luck