im not taking any of the cred for this discovery cos it`s Kafka`s from this thread:
kafka`s janis grow
its regarding the vent bought from screwfix, here: screwfix vent
i bought 5 of em (i know but there only £2 each), anyway got them today i gotta say these are just ideal for anyone wanting to use a pasv intake system, ive chopped one down and fitted it into the bottom of my grow cabinet, thus:
(appoligies for crappy pics)

its a 2 piece plastic vent that stops light from passing throo!! ideal
it can be set in 2 ways either as the normal `Z` shape or as the slightly less conventional `C` shape, which is perfect for my cabinet
the vent drops just below the bottom of my cabinet suckin air from directly under the box, heres a shitty pic:

i pull air out the top of the box using 2 pc fans sitting inside a long retangular cardboard box, which is taped over a large hole, cut flush with the top of the cupboard behind the lights; crappy pic:
edited to add: yes the box is the one that the mg sl came in (waste not want not!)

end shot:

pulls air like a dyson
all that remains is to fit the screen to the front of the cabinet behind the door to prevent light leakage and i`m finito(only took me 10 days)
heres a pic of the hole behind the lights to finish.

hope this info is of use to someone, it certainly worked for me.

cheers kafka


edited: cos i forgot the pic

i am quite interested in these..

how many would i need to vent a room that has a volume of 4.83m using a fan that extracts 660m3/h??

i worked out that my passive holes need to total 3.35m sq.. if i have a 6" extractor fan... is that right?

srewfix say that they have a free air flow/ move 6m2 of air, but dont give any dimensions of their size. they dont look to big to me. Would i need a shit load of em?

Cheech.

another piccie of them in use, each ones area is 2" X 9";



From http://www.uk420.com/boards/index.php?showtopic=28423

hmmmm.... been trying to come up with a neater baffle solution to my cardboard and sellotape blue peter madness. Trying to work out from those pics, can you stack them on top of each other? I have a couple of holes 4" x10" ish that I could gaffer the baffles into....? I see from screwfix they're telescopic upwards but are they inwards? maybe a short trip to hacksaw land would sort it....

'edit' - oops. soz so many questions I saw them in kafkas thread a while back too but dutifully forgot about it til now

peace,
Blab