T.O. 33B-1-1
The dry area is where film is unloaded and placed on hangers, prepared to be loaded in the automatic film
processor, loaded in cassettes or cut to support special inspections. No liquids or materials that could damage
unprotected film should be allowed in this area. The wet area is where development chemicals are mixed,
hand development is accomplished and other operations of this nature are performed. Wet hangers and other
wet equipment should not be permitted out of this area of the darkroom. These two areas should be
physically separated to prevent the wet chemicals, which can cause spots or other artifacts, from being
accidentally transferred to the film loading areas. Most dark room equipment such as the processing tanks,
dryers, and hangers are manufactured of stainless steel. The fixer solution is particularly corrosive, and
most other metals are readily attacked.
1.9.2.2
If possible, the dark room should adjoin the X-ray room or radiographic work area. A film-transfer cabinet
should be installed in the separating wall, particularly if a large volume of work is done. Film can be handled
efficiently without interfering with darkroom processing. The film-transfer cabinet must be lead lined if it
adjoins the X-ray room.
1.9.2.3
Proper ventilation SHALL be provided for the darkroom. The circulation of clean fresh air will reduce fatigue
and provide a healthier atmosphere. Light-tight ventilators SHALL be installed, the number depending on
the size of the darkroom.
1.9.2.4
Assuming a developing time of 5 minutes, one 5-gallon tank will develop 30 films an hour. The stop bath
tank should have a capacity equal to that of the developing tank. The capacity of the fixing bath tank should
be double that of the developing tank. The wash tank should hold from 20 to 25 gallons. Install the wash
tank so that films are placed in the tank at the outlet end. If dark room volume requirements must be
greater, use the above relationships to plan the additional facilities. The finish of the benches, walls and
f loor adjacent to the tanks must be adequate to protect against the action of chemical solutions and water
that may be spilled on them.
1.9.2.5
Film bins are desirable since they are light-tight and close automatically. The boxes of film can be stored
here in perfect safety and are readily available. For the mixing of chemicals enamel pails, several funnels
and stirring rods must be provided. Where films must be dried rapidly, film drying cabinets are necessary.
These dryers should have a filtered air intake, film racks, exhaust fan and heating element. It is best to wire
the fan and heating elements on the same circuit so the heating element cannot be turned on without the fan.
1.9.2.6
To minimize the fogging of undeveloped radiographic film by the safelights in the darkroom the following
provisions apply:
a.
General illumination should be indirect.
b.
Safelights should be suspended from be ceiling and SHALL be at least four feet from undeveloped/
exposed film.
c.
The ceiling should be white with the walls a light color.
d.
Only the minimum level of safelight needed to perform darkroom operations SHALL be allowed.
e.
Only safelight filters (6B or equivalent) designated for use with industrial radiographic film SHALL
be allowed.
f.
The manufacturer’s recommended bulb wattage SHALL not be exceeded.
1-72
Change 2
