Sink-level ventilation

[Ulrich Drolshagen]

In my darkroom it had been done by a shop specialized in the construction of venting systems. This is the outcome:


As you can see if you look closely, there is a large slit over the whole length of the duct. Above the intake is a silencer before it goes in to the housing of the vent. The difficulty in building such a construction is to make it in a way that the air flow doesn't generate noise. It works pretty well over the whole length of the table. At level high it sucks the cap from your head without much noise.
Since building this system I know where the term 'duct tape' is from, by the way.

[Jim C.]

but if you note, the samples on that page are localized extraction, including the slotted table-level one you linked to. The description states that it is intended to be attached to a flexible arm. Which of course is quite cool.

But I get your point -- indeed I could build something that sucks the air out from backsplash level. It could be a pvc pipe with holes or a narrow slit and hopefully I can get even draw. But the localized extraction thing is cool and may work better.

Yes, the example that I pointed to is to be attached to a flexible arm, Lenser posted a pic exactly what I was getting at, but you got the point,
it doesn't have to be a tube, I don't know what the fixation is with tubes. With a flat plenum it can be the whole back splash of the sink
and you get more useful space.

I've worked with localized extraction with flex tubes, while not in a dark room situation, it can be a royal pain.

[cyrus]

Yes, the example that I pointed to is to be attached to a flexible arm, Lenser posted a pic exactly what I was getting at, but you got the point,
it doesn't have to be a tube, I don't know what the fixation is with tubes. With a flat plenum it can be the whole back splash of the sink
and you get more useful space.

I've worked with localized extraction with flex tubes, while not in a dark room situation, it can be a royal pain.

I guess pvc tubes are just more accessible but I could use 4" square plastic fence posts or smaller roof drains etc which are rectangular, and thus also form a little shelf..
.

[cyrus]

In my darkroom it had been done by a shop specialized in the construction of venting systems. This is the outcome:
.

I have actually studied your setup before for ideas. Here's a question: why the U shape? why not just connect the left side of the manifold to the fan and shorten the length of the run, thus requiring a smaller fan, and less noise and no need for the sound dampner you have all the way on top. That dampner must reduce CFMs quite significantly, no?

[cyrus]

Cyrus, the exhaust (intake, actually) holes in that pipe just seem too small and specific to do an adequate job of sucking up fumes. The Kodak solution seems to me be the direct opposite in aerodynamic efficiency of the hole pipe design. This is one reason why it is so appealing (…it is also elegantly simple and protects the fan). Using a large single fan, depending on the manifold design behind it, and possibly not even requiring the manifold, air is withdrawn from behind the protective backsplash cowling, where it will pull in air from a great length on either side as it overcomes pressure in the center, resulting in adequate exhaust along all, or nearly all, of the sink all the time. As previously suggested, the smoke test will tell all.

\

Thank you, if I don't go with localized extraction using a flexible hose, this may be the best solution.

[Mot]

I use a Panasonic Inline Whisper Fan. The fan is very quiet and mounts remotely (in the attic). I set it up to suck fresh air in from outdoors and then blow into the darkroom through a HEPA filter mounted in a return air box. The fan uses flexible aluminum ducting. A sheet metal shop made a long slotted box that runs along the sink at the rear. The slotted box is attached to a hose that goes outside. My thought was that I would pressurize the room and the only exit for the air would be across the sink/trays. It is quiet and works very well although it is difficult to open the door when the vent is running.

[Jim C.]

I guess pvc tubes are just more accessible but I could use 4" square plastic fence posts or smaller roof drains etc which are rectangular, and thus also form a little shelf..
.

You would be building a 4" thick box or whatever thickness needed to accommodate you coupling to the fan, any dimension width and height out of sheet wood, plastic, etc.
Quick and dirty sketch.

[Larry Gebhardt]

Those fans are indeed known for being quiet. 250 cfm you say is enough? How big did you cut the holes in the pipe to be able to work with that cfm? Does the pipe draw evenly over the ra4 roller transport machine?

I used 4" drain pipe that already had the holes drilled in it in two rows. There's an 8' section over the sink and a 4' section over the roller transport machine. It's a bit hard to tell how evenly it draws. I put the end that was closest to the fan over the open end of the processor. It's very effective at removing the strong RA-4 odors. I suspect I could make it more even by covering some of the holes closest to the fan, but it's adequate for now.

[MrFujicaman]

It seems to me you could test the venting system with a smoke bomb from a fireworks store...

[cyrus]

It seems to me you could test the venting system with a smoke bomb from a fireworks store...

lol I'll stay with a cigar