Darkroom ventilation how-to

Hi All,
I will be doing a sort of redisign of my small (approx 1,5 x 3 meters) darkroom space on the occasion of getting in a new enlarger (Durst 138) and I thought it would be a good opportunity to install some kind of ventilation as well. Now, the room is located in the basement, the door leads to the staircase and there is a small window out.
Until now I have been working without a ventilator but opening the window now and then to get some fresh air (I work mostly in the night, once the kids are asleep).

The outer walls are pretty thick and strong (reinforced concrete...) and I cannot see drilling a hole there. My first idea was just to install a small fan ON the door to simply force some fresh air INTO the darkroom. Would that be enough or do I need also to find a solution for another ventilator sucking the air out? (the only idea I can think of is either drilling a hole in the glass or blocking the window from the outer side, putting the fan there and simply open the window...

Any ideas would be most welcome.

Thank you.

At least over here you can rent even machines with cylindrical diamond tipped drills. Thus making a nice hole in concrete seems within your reach, once you can get that room cleared before because of the mess (water spooling).

Cutting a hole in the window pane seems another way to go. There are more.

I would think you would need a fan sucking air out and on the opposite side of the room a vent allowing air to come in. My darkroom has three vents and an exhaust fan/hood. Bill Barber

You could make both an in and out vent on the door, with a small fan in the door (muffin fans are great) with a flexible duct running to the window to actively vent air out, and just a light proof vent in the door to passively admit fresh air.

You should have the exhaust drawing the chemical vapors away from you. For example in my darkroom the door vent and AC vents are behind me, the sink/trays are in front of me and the exhaust fan is above the sink/trays venting to outside the house.

http://www.jeffreyglasser.com/

If I understand correctly, you're 1.5x3 meter darkroom is within a larger room that has a window. Also, I assume that your darkroom is not used all that often (more than a few hours a week, spread over the week).

While personally I don't think ventilation is necessary in most cases for a typical b/w darkroom (i.e. no odd chemicals), your darkroom is pretty small. So in your case it's probably wise.

While you can drill a whole in concrete, I'd take a less intrusive approach. If you can (or want to) replace the window with a wood panel and install a vent great, otherwise:

• Install an exhaust vent over the sink, using something like a bathroom exhaust fan. Exhaust into the larger basement.
• Install an intake vent, with filter, opposite the sink.
• When the darkroom is in use, use an exhaust fan in the window, like this.

While not ideal, this should be simple and adequate.

My darkroom is also small - even smaller than yours! Ventilation is pretty important. Yes, you will need to suck out and have an air inlet. Ideally position these so that the airflow draws the tray fumes up and away from you. Small bathroom type extractor is adequate. Mine goes out through an external wall, and I found I had to make a light baffle over the fan or the light came back through - no big deal, just a bit of cardboard! My inlet is a hole to an adjoining room behind the bench that the enlarger sits on.

My last darkroom was in a basement, and what I did for ventilation was to modify a bathroom exhaust fan, which I mounted in a box and went through the ceiling/floor so that I brought clean air from the house above, filtered it and brought that into the darkroom. My preference is to bring more air into the room than is being vented out, so that the darkroom has a positive pressure relative to the rest of the basement - this keeps the dust from the basement getting into the darkroom. I had a passive vent from behind the sink to allow air to exit there, and go to the outside.

Good suggestions here. I would also recommend using less smelly chemicals. Maybe substitute citric acid for traditional stop bath (the Kodak stuff stinks to high heaven), etc.

Mark_S said:

My last darkroom was in a basement, and what I did for ventilation was to modify a bathroom exhaust fan, which I mounted in a box and went through the ceiling/floor so that I brought clean air from the house above,...

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In Europe those basement ceilings are from concrete or at least from bricks in old houses. Thus the same problem would arouse as going through the basement wall.

Thank you all for your tips and suggestions.
As I said, I am not going to drill ventilation holes in the concrete - and that means walls as well as ceiling. The door and the window are on the opposite short sides of the darkroom, so creating a draught would be possible. I'll visit the local equivalent of Home Depot this afternoon and see what they have on the shelves.

I think the best way indeed would be to plug the window-open on the outside and install a fan there and put a (light-tight and hopefully dust-proof) inlet in the door.

momus said:

Good suggestions here. I would also recommend using less smelly chemicals. Maybe substitute citric acid for traditional stop bath (the Kodak stuff stinks to high heaven), etc.

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I already use just citric acid for stop bath (as well as clearing kallitypes), I use Ilford fixer (certainly less smelly than the "local" Foma-Fix) or indeed alkalic fixer from W. Moersch which is practically odourless. The most smelly things that happen are some additives in 2nd baths when I am lith printing... But I have learned to use them one shot and then go immediately to the adjacent bathroom to put the print to wash and get some fresh air...

We put a lotta vinegar on our fish and chips you can dilute it and use for stop...

Lots if people use a lotta salt as well.

Mark_S said:

My preference is to bring more air into the room than is being vented out.

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That would mean your darkroom accumulates air, and will eventually explode!

Designing a ventilation system is not complicated. Air will flow from high pressure to low pressure, so the first thing is to decide how you want the air to flow. The best is to have it take chemical vapours away from you and contacting as little else in the process as possible, e.g. don't put your enlarger and paper store in the draught after the developing trays. Once you know how you want to direct the air, you put in an extraction fan at the outlet, or an inlet fan at the inlet, or both. The balancing of inlet and outlet is what determines the room pressure relative to its surroundings. If you have only an extraction fan, the room will be under slight negative pressure. The opposite is true for only a supply fan.

The next step is to add dust filtration, heating and/or cooling as you see fit. In my view, an inlet fan with a washable dust filter is the best arrangement, as that will keep dust out. If one has the luxury to do so, one can construct a fume hood over the developing trays or extend the supply and extraction via ducting, as is done for industrial facilities. If a fan is added to the extraction duct, it can be balanced with the supply fan through dampers or adjusting the motor speed. What would be a bad idea is sucking in unfiltered air, which will lead to a dust supply, so the room should not be under negative pressure relative to its surroundings.

It is not difficult to construct a light-tight inlet/outlet arrangement, and there are commercial options available as well.

dorff said:

That would mean your darkroom accumulates air, and will eventually explode! ............. In my view, an inlet fan with a washable dust filter is the best arrangement, as that will keep dust out................

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This has worked well for me. The fan is just a computer fan, so the flow of air is small, but enough to keep the air reasonably clean and much better than no ventilation. The darkroom is a small room inside a larger one, and there is minimal circulation in the larger one, but since I'm not in the darkroom 8 hours a day it works well enough.

I also agree with above suggestions to use minimal-odour chemicals, such as citric acid stop and low-acid or neutral or even slightly alkaline fixer to reduce SO2 odour.