Dark Room

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mshields

Senior Member
Location
Boston, MA
I'm doing a dark room which has a foyer associated with it. The door to the dark room is a conventional door and I believe there is supposed to be some kind of interlocking between the two doors in the foyer (one into the foyer from the hallway, the other into the actual dark room) and the lighting in the foyer.

i.e. such that the door to the dark room itself cannot be opened until the outer door is closed and the light in the foyer is off.

Does anyone out there have any experience with this. Looking for details showing how this is best accomplished, manufacturer's who provide such systems, etc.

Thanks,

Mike
 
The trick is to just have each door lock mechanically whenever the other is open...
Usual approach is a magnetic reed switch positioned to close contacts whenever a door is opened wired to a solenoid or magnetic plate that latches the opposite door closed. For safety as well as efficiency the latches should only operate when powered allowing exit should power fail.

I've also seen it done completely mechanically.
 

LarryFine

Master Electrician Electric Contractor Richmond VA
Location
Henrico County, VA
Occupation
Electrical Contractor
Neat idea, Dave. Each door must be closed for the other door (which, as you said, should be de-energized to release) to be de-energized, so you could use a pair of closet-door jamb switches to operate the electric jamb latches.

Standard magnetic reed switches break contact when a door is open, but these should make contact when a door opens. Of course, that means both latches will be energized 99% of the time, so they should be well-made and quiet.
 

Article 90.1

Senior Member
If you have the space it is safer to build a maze: http://www.sebastiandarkroomprod.com/darkroom_design.php A maze also lets air flow into the darkroom (make up) and out through the exhaust. If this is a personal darkroom, I would just have one door and either two light switches, or you could use a SPDT, one throw for room lights, one throw for dark lights; an either or set up. This is the set up in my wife's commercial darkroom.

I can see a gang printing darkroom using the double door set up. However, my concern would be egress in the event of a fire, or chemical emergency; just curious what the IBC would want to see here...
 
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