Ventilation specs for darkroom

[RodinalDuchamp]

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 (https://www.amazon.com/VIVOSUN-Inline-Booster-Noise-Grounded/dp/B01C82SZRM/ref=sr_1_3?gclid=EAIaIQobChMIy8D1isnE5QIVT9yGCh3XsQWYEAAYASAAEgIavvD_BwE&hvadid=174236493050&hvdev=c&hvlocphy=9011946&hvnetw=g&hvpos=1t1&hvqmt=b&hvrand=3026322456326025164&hvtargid=kwd-5221813225&hydadcr=8434_9618941&keywords=6+duct+booster+fan&qid=1572458687&sr=8-3)

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.

[Leszek Vogt]

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.

197016

Les

[adelorenzo]

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 (https://www.amazon.com/Hydrofarm-Active-Air-inch-Line/dp/B002JQ4N92/ref=sr_1_4?keywords=active%2Bair%2Bfan%2B4%2Binch&qid=1572470660&sr=8-4&th=1) 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...

[Tin Can]

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 (https://www.supplyhouse.com/Panasonic-FV-20NLF1-WhisperLine-240-CFM-Remote-Mount-In-Line-Ventilation-Fan?gclid=EAIaIQobChMI9tCDjojF5QIVUr7ACh2iYwRJEAQYASABEgLLmPD_BwE)

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 Broan® 6" Aluminum Wall Cap Round Duct (https://www.menards.com/main/bath/bathroom-fan-accessories/broan-reg-6-aluminum-wall-cap-round-duct/641/p-1444425974545-c-1453749026746.htm?tid=3981065963380321493&ipos=14)

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

[scheinfluger_77]

The question of air changes is a good one. IIRC some old darkroom books recommended 5-6 changes per hour. If that’s true you would not need a 240cfm fan for 252 cubic feet. I don’t remember where I’ve read that and I don’t really know what is appropriate, I’m really shooting in the dark on this.

[Pere Casals]

https://www.largeformatphotography.info/forum/showthread.php?153539-Darkroom-Ventilation-advice-please&p=1511600&viewfull=1#post1511600

[Maris Rusis]

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.

[Duolab123]

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 (https://www.amazon.com/VIVOSUN-Inline-Booster-Noise-Grounded/dp/B01C82SZRM/ref=sr_1_3?gclid=EAIaIQobChMIy8D1isnE5QIVT9yGCh3XsQWYEAAYASAAEgIavvD_BwE&hvadid=174236493050&hvdev=c&hvlocphy=9011946&hvnetw=g&hvpos=1t1&hvqmt=b&hvrand=3026322456326025164&hvtargid=kwd-5221813225&hydadcr=8434_9618941&keywords=6+duct+booster+fan&qid=1572458687&sr=8-3)

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?

[Drew Wiley]

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.

[RodinalDuchamp]

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.

[RodinalDuchamp]

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.
I believe everything you say but this is largely to put my wife at ease who worries. I've been processing for yeara without bother but as I get older she worries more

[RodinalDuchamp]

The question of air changes is a good one. IIRC some old darkroom books recommended 5-6 changes per hour. If that’s true you would not need a 240cfm fan for 252 cubic feet. I don’t remember where I’ve read that and I don’t really know what is appropriate, I’m really shooting in the dark on this.

I will peruse my copies of the negative and see if he mentions ventilations

[RodinalDuchamp]

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 (https://www.supplyhouse.com/Panasonic-FV-20NLF1-WhisperLine-240-CFM-Remote-Mount-In-Line-Ventilation-Fan?gclid=EAIaIQobChMI9tCDjojF5QIVUr7ACh2iYwRJEAQYASABEgLLmPD_BwE)

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 Broan® 6" Aluminum Wall Cap Round Duct (https://www.menards.com/main/bath/bathroom-fan-accessories/broan-reg-6-aluminum-wall-cap-round-duct/641/p-1444425974545-c-1453749026746.htm?tid=3981065963380321493&ipos=14)

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

Thank you. I dont live near a menards but that looks way easier to install than my first choice.

[Drew Wiley]

Every darkroom realistically needs adequate ventilation and fume extraction, no matter how innocuous you think your chemistry is. You might get away with being oblivious to the issue year after year, then suddenly get sensitized to something, or quickly develop respiratory problems devoid of any other explanation. It happens, more often than you might think. Even medical deductible expenses are going to cost you more than a good fan if that happens. You get what you pay for. $20 wouldn't even buy suitable ducting, not even a realistic intake vent. It all has to be light-tight or it's useless. Incidentally, I installed that Whisper 240 in-line fan for the darkroom remodel I'm working on right now. Pricey, but ideal. But my darkroom complex uses a huge external-mount Broan industrial squirrel cage - also quiet, but very powerful if there's an accidental spill of something nasty. Normally I use it at low power, and it's overkill for the average personal darkroom, but wonderful for my own needs.

[Merg Ross]

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.

[RodinalDuchamp]

Every darkroom realistically needs adequate ventilation and fume extraction, no matter how innocuous you think your chemistry is. You might get away with being oblivious to the issue year after year, then suddenly get sensitized to something, or quickly develop respiratory problems devoid of any other explanation. It happens, more often than you might think. Even medical deductible expenses are going to cost you more than a good fan if that happens. You get what you pay for. $20 wouldn't even buy suitable ducting, not even a realistic intake vent. It all has to be light-tight or it's useless. Incidentally, I installed that Whisper 240 in-line fan for the darkroom remodel I'm working on right now. Pricey, but ideal. But my darkroom complex uses a huge external-mount Broan industrial squirrel cage - also quiet, but very powerful if there's an accidental spill of something nasty. Normally I use it at low power, and it's overkill for the average personal darkroom, but wonderful for my own needs.

Correct. But that's precisely what I am trying to find out - how much ventilation in terms of cfm are ideal for a 250 sq ft room?

[Tin Can]

https://humanhealth.iaea.org/HHW/MedicalPhysics/DiagnosticRadiology/PerformanceTesting/Filmprocessinganddarkroom/darkroom_design_(IAEA).pdf

Read that, consider your usage

and it's Cubic feet not Square feet

[RodinalDuchamp]

https://humanhealth.iaea.org/HHW/MedicalPhysics/DiagnosticRadiology/PerformanceTesting/Filmprocessinganddarkroom/darkroom_design_(IAEA).pdf

Read that, consider your usage

and it's Cubic feet not Square feet

Thanks sorry my math skills are deplorable

[RodinalDuchamp]

For anyone interested:

(4) There should be at least 10 air changes per hour in the room to ensure removal of
chemical fumes from the area. The supply should be located so that it does not “short
circuit” and feed directly to the exhaust. A darkroom supply of 50% of the exhaust
rate is ideal.

[Tin Can]

Thanks sorry my math skills are deplorable

your math 6X6X7=252 is perfect, your terms were off

you have been very specific in yours posts

carry on regardless

[Tin Can]

For anyone interested:
So you will need a low volume fan, perhaps a computer fan will work


(4) There should be at least 10 air changes per hour in the room to ensure removal of
chemical fumes from the area. The supply should be located so that it does not “short
circuit” and feed directly to the exhaust. A darkroom supply of 50% of the exhaust
rate is ideal.

[Pere Casals]

(4) There should be at least 10 air changes per hour in the room to ensure removal of
chemical fumes from the area.

Beyond norms, the key is not to have turbulence. Air has to flow laminar from the emision sources to the extraction, in that way fumes are never breathed. If we have turbulence we always breath some fumes, and we need a lot of air changes to keep fumes concentration low, but it will never be zero. With a properly designed system we breath zero fumes.

A properly designed system is essential when we use some kind of chem.

[Tin Can]

I am out as Pere and Drew tango

Make up air is important and can be very cold or hot depending on location, climate

[Tin Can]

No dancing? It's Hell-O-Ween!

Old threads on DR ventilation found on bottom of current page, some go back 20 years.
https://www.largeformatphotography.info/forum/showthread.php?74498-Darkroom-ventilation-fan&p=709987&viewfull=1#post709987

https://www.largeformatphotography.info/forum/showthread.php?61751-Darkroom-ventilation-problem&p=583499&viewfull=1#post583499

https://www.largeformatphotography.info/forum/showthread.php?10788-Garage-Darkroom-Ventilation&p=81143&viewfull=1#post81143

https://www.largeformatphotography.info/forum/showthread.php?4852-Bad-ventilation-in-darkroom&p=30262&viewfull=1#post30262

https://www.largeformatphotography.info/forum/showthread.php?2915-darkroom-ventilation&p=16335&viewfull=1#post16335

[Drew Wiley]

A computer fan????? That's like a mouse dueling a mountain lion. Wrong Holiday. This is Halloween, not April Fools Day.

[adelorenzo]

I was reading Tim Rudman's toning book last night and he also recommends a minimum of 10 ACH.

[Tin Can]

OP is trying to figure out DR ventilation for a 6 X 6 X 7ft shed. 252 cubic feet

He needs a small fan, 240 CFM is too big by a factor of 10


I was reading Tim Rudman's toning book last night and he also recommends a minimum of 10 ACH.

[adelorenzo]

OP is trying to figure out DR ventilation for a 6 X 6 X 7ft shed. 252 cubic feet

He needs a small fan, 240 CFM is too big by a factor of 10

I wasn't making any comment on the size of the fan required, I was just giving the OP another data point for recommended air changes per hour.

[Tin Can]

I know you were. I was trying to repeat his needs

All good


I wasn't making any comment on the size of the fan required, I was just giving the OP another data point for recommended air changes per hour.

[Drew Wiley]

You don't know what you're talking about, Tin Man, or I am confusing you with a character in Wizard of Oz? If you take 240CFM, factor in hydrostatic pressure outside on a rainy day, or even in a humid climate, and then air friction from ductwork that cannot be straight because it has to prevent light entering and may very well be corrugated for ease of installation, the real world capacity is about half that air volume at best. Then one always needs a boost factor, even if ordinarily running it at lower volume, in case there's a spill of something you want rapidly exhausted, or during mixing of some concentrated chemical. So a fan of at least 180 cfm is called for, or even better, 240 because there's such an excellent in-line option in that case. That would be the routine specification for even a bathroom that size, where mainly just water vapor is involved, unless the climate is routinely arid. What one doesn't want is a cheap ceiling-mount propeller-style fan that is as noisy as a gas lawn mower.

[Tin Can]

Welcome Wizard of OZ

[Drew Wiley]

Thank you. I have a pair of tinsnips you can borrow if needed.

[Jac@stafford.net]

One question concerns how far we need to move the air - is push or pull or a combination of both better and under what circumstances?

[Drew Wiley]

Pulling air is always more efficient than pushing it. An in-line fan somewhere in between, with ducts both directions, is a compromise. But there are also logistical issues. It's fairly easy to locate a high-quality in-line fan in an attic, and it can be set up to service more than one room or duct line. Wall fans have to be shallow to fit inside stud spacings, and sometimes ceiling fans have to too; but these types, if squirrel-cage design, are less expensive than other squirrel-cage options. A more elegant alternative is a weatherized externally-mounted fan or combination of them, which pulls the air as well as isolates noise. More money. I use a large version of one of these, plus a small booster fan connected to a portable fume arm which I can place just above something noxious being mixed, and does not need to be quiet because it's only temporarily used. It's own flexible duct exits into the main fume hood.

[UnaSutherlands]

To be honest, I don't understand anything about air conditioners at all. Of course, I tried to figure it out myself, but each time I only made it worse. Although everything is simple in the drawings. I don't understand why this is so.

[Drew Wiley]

Let me repeat, pulling air is ALWAYS more efficient than pushing it. But sometimes an intermediate in-line fan is the best logistical compromise. But knowing that doesn't mean I always get it right. Last time I crawled into an attic and installed a big in-line fan using a headlamp, I accidentally hooked up the wiring wrong. When I turned it on down below, it was blowing air back down instead of pulling it up! So back to that cramped attic I went, to correct it.

[Scraps]

Let me repeat, pulling air is ALWAYS more efficient than pushing it.

Thanks for bringing up that point. I want to set up ventilation via a portable floor air conditioner since it extracts a significant amount of air as well as cooling and dehumidifying the basement room in summer months. Since pushing air - as in laundry dryers - is inefficient at pushing air to the outside I should try using an in-line fan. It'll make more sense to install it as near as possible to the window since the basement window is 7.5' up the wall and will require extra piping adding more distance than is recommended for these dryers. I'll treat it the way you installed an extraction fan in the attic.