Darkroom ventilation

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My darkroom is about 880 cu. ft. Does anyone know how to specifically achieve healthy, light free ventilation? I have a crawl space door in the area which goes under the house. My husband thinks some kind of fan would draw out the chemical fumes but I am worried about drawing them under the house. I am also worried about dust and light leaks. He says there is no light problem from under the house. Do you know of a specific type of fan or air filter which works well in darkrooms? Wendy

-- Wendy Fowlie (wendy4413@aol.com), August 31, 2000

Answers

Just add a normal [nonlighted] bathroom fan [the quietest you can find since you'll be listened to it a lot], with its own switch, and vent it down, provided there are, indeed, no light leaks introduced from the basement. The fumes shouldn't harm anything important [excluding unwanted critters] there. They might be a little humid, but you won't be using it that much. Keep in mind that if you are using an exhaust, then you must use a lightproof valve to introduce fresh air to the darkroom to replace that removed. I believe they are available at Porter's.

-- Alec (alecj@bellsouth.net), September 01, 2000.

Good ventilation is essential for long-term health. Not only do you need a good fan, but you also need a good vent, because you can only draw air out if you can let the same amount in. I did a quick search on the internet, and there are a number of places that sell fans and vents designed specifically for darkrooms. Start at http://www.warehousephoto.com/darkroom4.htm.

-- Ed Buffaloe (edbuffaloe@unblinkingeye.com), September 01, 2000.

Wendy,

I installed an ordinary bathroom exhaust fan in the ceiling of my darkroom, which vents into the attic. Six feet of four-inch exhaust hose looped around a couple of times insures that no light leaks back throught the fan. To insure clean air coming in, I cut a hole in one of the darkroom doors and installed a little homemade baffled box, which contains an ordinary furnace air filter. Thus, when all doors are closed and sealed, and the fan is running, the air coming in to the darkroom is filtered through the furnace filter. This cuts down on dust quite a bit. Hope this helps, ;^D)

-- Doremus Scudder (ScudderLandreth@compuserve.com), September 01, 2000.


The easy answer is to buy a darkroom fan and darkroom vents. These are manufactured devices that are light proof and have a fan or not.

I would be careful venting into a crawl space. I would run a duct from the exhaust to the outside.

For 880 cf, you want a fan of between 88 and 220 cfm. That will give you between 6 and 15 air changes per hour. Remember to take into account that ducting will reduce the air flow of the fan due to backpressure (technically static pressure losses).

The best setup for a darkroom is a combination of positive and negative pressure ventilation. You blow filtered air into the darkroom and you power exhaust air at the same time. You size the fans such that you blow in slightly more air than the draw out. This way any leaks leak air out of the darkroom, rather than in carrying dust.

THe best place to exhaust is over the sink. This way the chemical vapors and dusts are removed closest to the source. The absolute best way is via a slot hood. This is an opening about 1-2 inches high the width of the sink. This is the exhaust port. You then size the exhaust fan to suck about 200-400 cfm throught the slot. Antyhing from the sink rises slightly and then back and out the exhaust. I built this for my sink and it works great.

BTW my background includes industrial ventilation design for contaminant control. So I am giving you advice to make a GREAT setup. The other posts will work, maybe not as well, but they will work. The big thing is to exhaust near the source and get enough airflow.

-- Terry Carraway (TCarraway@compuserve.com), September 01, 2000.


THanks for all of the info. I have just ordered a darkroom fan and louver combination from Warehouse Photographic. After a Home Depot trip yesterday, I was frustrated. No one knew anything. Calls to three photo shops had gotten me nowhere either. You folks on this site are a wealth of knowledge and very generous in your willingness to share it. Thank you. Wendy

-- Wendy Fowlie (wendy4413@aol.com), September 01, 2000.


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