I am building a darkroom and I was wanting to know abotu intake and outtake air flow. Where an you buy the vents? I am builidng outside and this will be a free standing building. Also I am on spetic and was wondering where you dump chemicals? Can you dump in the septic or not? I will be doing quite a bit of development and printing. I just am trying to figure out these question as I have already broke dirt and will be framing the darkroom part in a week or so. Thanks.