Darkroom ventilation help?

I am modifying my darkroom. The complete work area is not bigger than 2,10m x 1,80m. I have bought a Nova Washmaster-Eco Archival Print Washer recently, so, by the time the darkroom will be finished, I would be able to print FB paper as big as 12x16, and even 20x16 washing manually.
I am going to incorporate a sign (1,75m x 0,65m x 0,20m) that I am making right now and I will also put an Extractor Hood just above it. I have taken this idea: Dead Link Removed. I will use galvanized ducts to take the air out, and an appropriate light tight louver that will be located in the upper side of the door. (Dead Link Removed, for example).
The question is: How many meters cubic per hour (M3/h) (or fpm, if you prefer) should the fan be able to move? In other words, which fan do you recommend me to buy?
By the way, I would like to get some different ideas about how I could ventilate my darkroom, which kind of vent hood, fan, etc. I also appreciate any idea about what I should add to my project. This is the time to design, since nothing has been done yet.
I am annexing a layout of my future darkroom.
Thanks,
Henry.

I have 70 sq meters of floor space and I use two 600 cfm fans. One, I spent a great deal of money on from Calumet, the other from Grainger ( a wholesale hardware store here in the US)

They do a pretty good job but over kill for what you have.

I might suggest a high volume, low noise bathroom fan. Many can move 125 cfm and the louder ones are cheap, so there is quite a price range out there.

Henry,
I'm going down this road myself, will keep you posted.
Pat

if you're not doing color work or using exotic chems I'm really not sure why you'd need to build any ventilation. Most B/W 'chems' are basically 'salt water'...

You might give thought to a range hood. They are fairly inexpensive and have an extra light built in. Placed over a sink, will help pull extra moisture and fumes from the chems. Added bonus is they can be used to recirculate air through a charcoal filter if you dont want to vent outside.

Vent Axia makes great fans for darkrooms I have them in my film processing rooms and they do the job fine. see link attached for information http://www.vent-axia.com/range/t-series-darkroom-model.html

Years ago Kodak put out a book on building a darkroom. They suggested a minimum of six changes of air an hour. I like several times that. Different people react differently to input, be it medication, fumes or what. Panasonic makes some very good, powerful and quiet fans. I have used mine for five years without problem or noise. Much has been written here and the LF Forum if you wish to search.

A common mistake is to put the exhaust over the sink so the fumes come up from the trays into your nose and then maybe out the exhaust. A good idea is to put the exhaust on the opposite side of the sink from you so the fumes go to it rather than you. Input one side of the room, exhaust other side, you in between. Try a little smoke and see if all the air in the room is moving through or just a path.

I do B&W using pyro developer. The instructions from the vendor warn to use a chem mask while mixing the powder because it can cause cancer. I am allergic to ammonia so some fixers can knock me flat. Metol wipes out some people. Some go for years without a problem then, as Bob Carrie told us, have to get out of the darkroom and never come back.

There is a lot of argument on this subject. I think it is because people react differently to input, do not look at the possible problems long term, and may be looking for a cheap fix.

John Powers

Here's an angle you might want to consider.

In my darkroom I chose to install two identical, matched fans units. They are the industial blower type and can move a lot of air. One of them blows to the inside, the other blows to the outside. They are wired through the same speed control so that whatever speed I set, they both move the same amount of air at the same time.

The idea was that I wanted to strike a balance. On the one hand, I didn't want to create a slight vacuum by only removing air from the room. This would have resulted in the sucking in of dust through every crevice in the darkroom - not to mention whenever anyone opened the door, or if I had install a passive intake vent.

On the other hand, I also didn't want a slight positive pressure resulting from only blowing air into the room. While this would have eliminated the dust issue, it would also have forced those wonderful-smelling-to-me darkroom odors (I just love the smell of an acid fixer!) back into the house where my wife and son did not share my enthusiasm for them.

But by installing a matched input/output set I achieve a perfectly neutral pressure, while at the same time changing the air continuously when they are active. And using a speed control let me install overkill capacity with the ability to throttle it back for normal use. But in the event of an emergency I can crank them up and move enormous amount of bad air outside in short order without worrying that any of it will seep into the larger house.

I once spilled a little glacial acetic acid into the sink. No major disaster, but I was very glad I had installed the overkill emergency capacity. Cleared the darkroom completely in under a minute.

Ken

P.S. I later decided to filter the incoming air using custom cutout portions of a furnace filter. I made sure to filter both the incoming and outgoing fans to preserve my "matched" configuration. My output draws air from near the ceiling, while my input directs air down to the floor.

Ken Nadvornick said:

The idea was that I wanted to strike a balance. On the one hand, I didn't want to create a slight vacuum by only removing air from the room. This would have resulted in the sucking in of dust through every crevice in the darkroom - not to mention whenever anyone opened the door, or if I had install a passive intake vent.

Click to expand...

If you don't want dust, you don't do you, it is a good idea to seal the ceiling. I had open rafters in the basement when I built my 11x13 foot DR. I framed in the 2x4s for the walls and then paneled them and the ceiling with 1/8"x4'x8' semi gloss white panel. This was painted black around the two enlargers. All joints were sealed with white duct tape. Intake air was filtered with a good quality furnace filter. The only dust I have is tracked in through the door. I vacuum before I print.

John

I have looked into how.. I will use an inline fan and fit it into Air con duct. place the vents over the sinks and tray area. A couple of 90 degree bends and out through the wall. A cover with bug mesh and seal around the duct and where in business. A small fan in a baffle to bring in fresh air down low. This will also create a convection effect as well.
Hope this helps
Pat

This is my solution:



The system is made by Helios and is made from these components.



The system is *very* silent as the fan is capsuled and there is a noise silencer built in. It is nothing which you want to install yourself as there are some pitfalls which generate noise if not handled correctly. You'll need a louver with dust filter somewhere.
Building a ventilation into a darkroom is easy. Building an efficient one which does not make noise is very difficult. Fans used in toilets are inapt as you stay in a darkroom for hours not for minutes.
My vent transports 380m³/h at full speed. This is about 15x the volume of my darkroom. Usually I run it on step 1. It is practicallly noiseless then. On step 2 it is barely hearable. I can run it conveniently up to step 3. Step 4 and 5 I rarely use. On step5 it is appr. as noisy as our kitchen vent on step 1.

Ulrich

Ulrich,
That is similar to what I propose to build. How do you introduce air into the darkroom?
Pat

largeformat pat said:

Ulrich,
That is similar to what I propose to build. How do you introduce air into the darkroom?
Pat

Click to expand...

There is a large louver with a light trap in the door. It is made with a filter to keep dust out.

Ulrich

Dears Ulrich and Pan: Do you think that vent the entire sink long will be as efficient as a vent hood equally long?
Henry.

I feel a hood would require a fan just the same. A hood would take up more area. I propose to place the duct behind overhead cupboards. Also with duct I was going to place it closer to the tray area and get more fumes removed with the fan not having to work so hard. A hood will access a larger area.
Pat