I'm planning on building a fairly small drobe, likely looking at nothing more than 2-4 plants. Next to the site I have in mind is a chimney for a fire which is never used. The question is, if I am able to use a fan to extract up the chimney, is there likely to be any smell floating around the house if I don't use a carbon filter? Smell has never been an issue when I've grown in the past so I'm really not sure what sort of measures are sufficient. Additonally, with such a small grow and the air being vented out the chimney, is there any realistic chance of my neighbours catching a whiff if I'm not using a filter? A former policeman who works at the same place as me and whose views about weed I'm unsure of lives next door so him smelling it is not an option.

If I do use a filter, is it going to be sufficient to neutralise unwanted odours if for whatever reason I have to temporarily vent into the room rather than up the chimney?

Edit: One more question: how much noise do the RVK 100 or 125 fans make? I have a couple of pcs, one of which has some pretty loud fans - is it likely to be louder than the PC or will the PC fans be a pretty good cover for any noise the extraction fan makes? Another thing I had considered is simply using several 120mm PC fans to vent the drobe for cheapness' sake. Is this likely to work and if so is there a way in which I could hook these fans up to a CF if needed?

def need a cf, i wouldn't dream of growing without one, even up the chimney the wind will catch it and swirl it straight down your street,

yes, that's what they do

Use a carbon filter-period.

Might be just a few plants but with ex-plod next door-why take a risk ?

id say use a filter mate. dont want the smell drifting down the chimney into the fireplace. at the moment i'm having to extract into the same room and the smell is there, just no where near as much. good luck, whatever you choose to do fella

living in a second floor flat i've found that the odour is dense and without a filter tends to attract the attention of my neighbours below who have the privilege of extracting their shit air out with my floral loveliness. So yeah, Carbon Filter f def.

Thanks for the quick responses guys, guess I'll be forking out the extra for a filter

Defo worth the money for peace of mind m8, i wouldnt grow anywhere without a filter