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Thread: Ventilation specs for darkroom

  1. #1

    Ventilation specs for darkroom

    I will be repurposing an old shed for temporary procession of sheet film. The entire space is 6'x'6 roughly and the roof peaks at about 7' so total volume is approximately 252 sq feet. I am trying to figure out how much ventilation I require to stay on the safe side. I am looking at this fan currently:

    6" fan

    It ::claims:: to do 240cfm, so from my very poor math that means the fan would circulate 1 shed's worth of air volume per minute. Is this sufficient? I will be using mostly HC110 and standard kodak fixer but I will occasionally use some pyrocat.

    The ducting will be placed directly over the developing tray and fixer tray at around waist height so that hopefully most fumes are sucked out before they reach my nose - that's the idea anyway.

  2. #2
    Les
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    Re: Ventilation specs for darkroom

    Your fan example is an inline type....I just peeked down the page and it shows the uses (as I suspected). What's more important, the specs show no sonces. What that means to me, that this thing will create enough racket-noise....that it will vibrate you right out the door.

    OK, kiddn aside, I'd install couple quiet fans just over the sink/dev area....this may have to be done in custom casing....or using larger computer fans (also quiet) whichever the number of them you use. The air should be pushed outside via larger funnel (6"+) with minimum of elbow obstructions and without the need for inline fan. Whatever you do, make sure you have immediate access to these fans, just in case something goes ker plunk and you may need to replace one or two.... Having additional opening in the room (like cracked window, etc) will certainly help in cross ventilation.

    Being in such small space, you'll be v. close to those fans; therefore, the quieter the better. I've installed Panasonic and like those for quietness....tho the Broan (also quiet type) are v. nice as well. Not sure if the latter is still being made. I mean without saying, that quiet solution will likely be more costly.

    I've installed these as well.

    Click image for larger version. 

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    Les

  3. #3
    adelorenzo's Avatar
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    Re: Ventilation specs for darkroom

    I have a similar ventilation setup and I used an inline duct fan similar to that one. I have a hard time believing that one of those would do 240 CFM. Mine was a 5-inch model and it did about 50 CFM. I replaced it with one of these which tripled my ventilation. It is much, much better. I have it on a speed control on the lower settings its not too bad but on max it's pretty darn loud.

    If that fan is giving you almost 60 air changes per hour that would be pretty crazy, especially for the relatively benign chemicals you are using. My system gives me about 12 air changes per hour which I think is good and I'm doing toning and stuff that is much worse than developer and fixer.

    Also: If this is just for temporary use I wouldn't bother with ventilation at all. Not with just developer and fixer. But that's just me...

  4. #4
    Tin Can's Avatar
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    Re: Ventilation specs for darkroom

    Your space is small which will vary widely in temp, odors and toxins

    Your indicated choice may work, but I doubt it equals a WhisperLine 240 CFM Remote Mount In-Line Ventilation Fan

    I have used the panasonic in 8000 cubic feet, which was too air tight and didn't move much air until I found a way to add makeup air. It was a one room studio, DR and living space.

    I am about to put the same one in a 1500 cubic feet bedroom now DR with filtered makeup air.

    You may as well try the $20 fan, I have looked at them in box stores.

    Install a flapper to keep birds and bugs out. This one Broanģ 6" Aluminum Wall Cap Round Duct

    It survived inner city ghetto and nobody screwed with it,
    [/URL]
    sin eater

  5. #5

    Re: Ventilation specs for darkroom

    The question of air changes is a good one. IIRC some old darkroom books recommended 5-6 changes per hour. If thatís true you would not need a 240cfm fan for 252 cubic feet. I donít remember where Iíve read that and I donít really know what is appropriate, Iím really shooting in the dark on this.
    --- Steve from Missouri ---

  6. #6

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    Re: Ventilation specs for darkroom


  7. #7
    Maris Rusis's Avatar
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    Re: Ventilation specs for darkroom

    First establish what fumes your chemistry will produce. If the fumes are irritating or toxic then you need a effective ventilation arrangement that pulls the fumes out of the darkroom before they get to your face. If you use smell-free chemistry then the only volatile is water vapour and you don't need a ventilation system at all. The commonest and nastiest fume producer in a black and white darkroom is acetic acid stop bath. There is no reason to use it. Change to odorless citric acid stop bath and the problem goes away at no cost.
    Photography:first utterance. Sir John Herschel, 14 March 1839 at the Royal Society. "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..".

  8. #8

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    Re: Ventilation specs for darkroom

    Quote Originally Posted by RodinalDuchamp View Post
    I will be repurposing an old shed for temporary procession of sheet film. The entire space is 6'x'6 roughly and the roof peaks at about 7' so total volume is approximately 252 sq feet. I am trying to figure out how much ventilation I require to stay on the safe side. I am looking at this fan currently:

    6" fan

    It ::claims:: to do 240cfm, so from my very poor math that means the fan would circulate 1 shed's worth of air volume per minute. Is this sufficient? I will be using mostly HC110 and standard kodak fixer but I will occasionally use some pyrocat.

    The ducting will be placed directly over the developing tray and fixer tray at around waist height so that hopefully most fumes are sucked out before they reach my nose - that's the idea anyway.
    Kodak fixer has strong odor, you might consider an alternative.
    Pretty small space. Maybe a drum and a roller?

  9. #9
    Drew Wiley
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    Re: Ventilation specs for darkroom

    Positioning of your exhaust duct is important. You want air pulled away from you over the sink and through the wall behind the sink. Then you need a light proof air intake vent behind you of sufficient size. 240 cfm is adequate for a small area like that. I recommend a Panasonic squirrel-hair fan and a variable-speed switch; very quiet.

  10. #10

    Re: Ventilation specs for darkroom

    Quote Originally Posted by Duolab123 View Post
    Kodak fixer has strong odor, you might consider an alternative.
    Pretty small space. Maybe a drum and a roller?
    Odor doesn't bother me but potential damage to my lubgs does. At this point after how much time I've spent experimenting and getting my d76 and pyro processes down I can't start over adding a new variable. It's much easier to find a decent vent solution than spend months figuring out drum processing. If you look at threads in my history you will see I'm a bit of an extremist when it comes to my film process.

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