Question on DIY darkroom ventilation

[gdi]

I was using a Nova tent in my unfinished basement darkroom for my printing trays and have set up a 6” duct fan to blow into the large bottom hole in the tent,inflating it, and then exiting at the top of the tent. I have routed that to a basement window with a dryer vent flap installed. There are a couple of problems with this - 1- it blows air from the floor up to the ceiling to extract fumes, right by my face, and 2- it is a PITA to go from the enlarger station outside to the tent and back.

So, I am currently using printing trays on a table in the open outside the tent. I light proofed my entire basement and the area is pretty large - so it isn’t a tight space. But I likely going to set up some form of fume extraction system and the most obvious approach to me is a 4“ diameter PVC pipe with holes drills in one side to run the length of the table a few inches above the trays connected to some flexible hose (6”) or more rigid 4” PVC pipe and adapting and inserted the duct fan in-line. And I would of course vent this out the window.

I have found some materials that my make this easier (though costlier!) but I want to see if anyone has any experience with it . It is Powertec dust collection hoses and pipe- it all comes in 6” and has couplers, pipe and hose. Does anyone have any experience with this type of dust collection system? I can’t see why it wouldn’t work to pull fumes as easily as dust. Also I am trying to decide if I should use 6” or 4” as the initial exhaust section over the trays, and then expand those to 6”. It seems having a smaller diameter initially may increase the air flow and draw the fumes from the trays into the system more efficiently than a larger diameter - but I’m not sure if it will make a huge difference - again, any experience or views on these ideas?

Many thanks!

[Larry Gebhardt]

I think a vent fan the draws air from above the trays would be adequate. I use a vent fan connected to a 4” perforated drain pipe place at the back my sink. It seems to work fine. I’m not that worried about the chemicals I use in the darkroom, but I like that it gets enough fumes that I don’t smell them.

A 600cfm wood working dust extractor seems to me to be overkill. I’d build a fume hood before I went with that.

[Maris Rusis]

Fume extraction is a vexed thing so for my last and best darkroom I eliminated it entirely.
Because I do only black and white work I can use odourless developer, odourless stop bath, and odourless fixer. The no-smell stop bath and fixer cost a little more but with no fumes to extract a fume extractor ($$$) is not needed.
By far the worst smell is acetic acid stop-bath but there is no reason to use it. The citric acid based alternatives work well and don't pong.

[Tin Can]

Fume extraction is a vexed thing so for my last and best darkroom I eliminated it entirely.
Ditto

Because I do only black and white work I can use odourless developer, odourless stop bath, and odourless fixer. The no-smell stop bath and fixer cost a little more but with no fumes to extract a fume extractor ($$$) is not needed.
By far the worst smell is acetic acid stop-bath but there is no reason to use it. The citric acid based alternatives work well and don't pong.

[gdi]

I think a vent fan the draws air from above the trays would be adequate. I use a vent fan connected to a 4” perforated drain pipe place at the back my sink. It seems to work fine. I’m not that worried about the chemicals I use in the darkroom, but I like that it gets enough fumes that I don’t smell them.

A 600cfm wood working dust extractor seems to me to be overkill. I’d build a fume hood before I went with that.

I agree, I was not planning to use a big dust extractor - just utilizing the pipe/hose components. I think your approach is what I’m aiming for and I’m glad it works well!

Thanks!

[gdi]

Fume extraction is a vexed thing so for my last and best darkroom I eliminated it entirely.
Because I do only black and white work I can use odourless developer, odourless stop bath, and odourless fixer. The no-smell stop bath and fixer cost a little more but with no fumes to extract a fume extractor ($$$) is not needed.
By far the worst smell is acetic acid stop-bath but there is no reason to use it. The citric acid based alternatives work well and don't pong.

I process mostly (95%) B&W, but will do some color film processing on occasion (no printing) and I can mix my chemical under the fan as well prior to developing in a Jobo.

Thanks

[Tin Can]

While I don't run a power vent

In winter a big humidifier is under the darkroom sink 24/7

The MERV 16 HVAC filter pulls closeby

in addition this is a leaky old house and that is how I like it

I would not raise a baby in it

[Doremus Scudder]

Keep in mind that if you have a length of pipe with holes drilled in it and are drawing the air from one end, the far end will have much less air flow than the one near the extraction end. You can compensate for this somewhat by making smaller holes spaced farther apart on the extraction end transitioning gradually to larger, more closely-spaced holes at the far end.

If you're planning on a 4-inch pipe, you'll likely find that you need a fan with a fairly large capacity to move enough air to give you adequate ventilation. My darkroom has a 3-inch pipe running the length of the sink under a shelf over the back of the sink. It's just about 4 feet long. The holes at the far end definitely pull less air that the exhaust end, but that's at a place where I only have developer trays. The more-efficient end is positioned over stop and fixer trays.

Best,

Doremus

[domaz]

I have an inline duct fan that vents air outside (exiting via a standard dryer vent) and ducting that runs to the darkroom. In the darkroom I have a piece of flexible hose that sits above my stinkiest tray (the fixer usually) and pulls air from it. It seems to work well, occasionally I do soldering of small electronics and the solder smoke will get pulled right into the duct and not linger in the darkroom. It seems sufficient for a darkroom of "standard toxicity".

[gdi]

I hadn’t thought of progressive holes along the pipe - I’ll keep that in mind!