DARK ROOM

Lec. 6 د.غسان علي
THE DARKROOM

The primary function of a darkroom is to provide a completely darkened environment in which x-ray film can be handled and processed to produce diagnostic radiographs. The darkroom must be properly designed and well
equipped.

Room Requirements
A well-planned darkroom makes processing easier. The ideal darkroom is the result of careful planning and must have the following characteristics:
1. Convenient location
2. Adequate size
3. Correct lighting equipment
4. Ample work space with adequate storage
5. Temperature and humidity control

Location and Size
The location of the darkroom must be convenient; ideally, it should be located near the area where x-ray units are installed. The darkroom must be large enough to accommodate film processing equipment and to allow ample work space. A darkroom should measure at least 16 to 20 square feet and provide enough space for one person to work comfortably.

The size of the darkroom is determined by the following factors:

1. Volume of radiographs processed
2. Number of persons using the room
3. Type of processing equipment used (processing tanks
versus automatic processor)
4. Space required for duplication of films and storage

Lighting
As the term “darkroom” suggests, this room must be completely dark and must exclude all visible white light. The term light-tight is often used to describe the darkroom. To be considered light-tight, no light leaks can be present. Any white light that “leaks” into the darkroom (e.g., from around a door or through a vent) is termed a light leak. In a darkroom, when all the lights are turned off and the door is closed, no white light should be seen. Any white light coming around the door, through a vent or keyhole, or through a wall or ceiling seam is a light leak and must be corrected with weather stripping or black tape. As previously discussed, x-ray film is extremely sensitive to visible white light. Any leaks of white light in the darkroom cause film “fogging.” A fogged film appears dull gray, lacks contrast, and is nondiagnostic.
Two types of lighting are essential in a darkroom, as follows:

• Room lighting:

Incandescent room lighting is required for procedures not associated with the act of processing films. An overhead white light that provides adequate illumination for the size of the room is necessary to perform tasks such as cleaning, stocking materials, and mixing chemicals.

• Safelighting:

The special type of lighting used to provide illumination in the darkroom is termed safelighting. It is a low-intensity light composed of long wavelengths in the red-orange portion of the visible light spectrum.

Safelighting provides sufficient illumination in the darkroom to carry out processing activities safely without exposing or damaging the film.

Safelighting does not rapidly affect unwrapped x-ray film and does not cause film fogging. A safelight typically consists of a lamp equipped with a low-wattage bulb (7.5 or 15 watts) and a safelight filter. A safelight filter removes the short wavelengths in the bluegreen portion of the visible light spectrum that are responsible for exposing and damaging x-ray film. At the same time, a safelight filter permits the passage of light in the red-orange range; consequently, the illumination in a darkroom is red. Most x-ray films have a reduced sensitivity to this red-orange range and are not affected by minimal exposure to the safelight. Under safelight conditions, it is necessary to maintain
an adequate safelight illumination distance and to keep film handling times to a minimum. Films that are unwrapped too close to the safelight or exposed to safelight illumination for more than 2 to 3 minutes appear fogged. A safelight
must be placed a minimum of 4 feet (1.2 meters) away from the film and work area, and unwrapped films must be processed immediately under safelight conditions.

A number of safelights with different types of filters are available for use in the darkroom. Some safelights are used exclusively with intraoral films, some are used exclusively with extraoral films, and others are designed for use with both. For example, a good universal safelight filter recommended for use in a darkroom in which both extraoral screen films and intraoral films are processed is the GBX-2 safelight filter by Kodak.

Recommendations for specific safelights and filters depend on the type of film (intraoral or extraoral) and are provided by the film manufacturer; such information is indicated on the outside of the film package.




Miscellaneous Requirements:

Darkroom work space: must include an adequate counter area where films can be unwrapped before processing. A clean, organized work area is essential; the work area must be kept absolutely clean, dry, and free of processing chemicals, water, dust, and debris. If an unwrapped film comes into contact with any such substance before processing, an “artifact” results, and the quality of the dental radiograph is compromised.

Darkroom storage space: must include ample room for chemical processing solutions, film cassettes, and other miscellaneous radiographic supplies. Storage of unopened boxes of film in the darkroom is not recommended; a reaction between the fumes from chemical processing solutions and the film emulsion may occur that will result in film fogging. Boxes of opened extraoral film, however, must be stored in the darkroom. A light-tight storage drawer is necessary to protect opened boxes of unexposed extraoral film.

The temperature and humidity level of the darkroom must be controlled to prevent film damage. A room temperature of 70°F is recommended; if the room temperature exceeds 90°F, film fogging results. A relative humidity level of between 50% and 70% should be maintained. When humidity levels are too high, the film emulsion does not dry. When humidity levels are too low, static electricity becomes a problem and causes film artifacts.

A utility sink with running water is also useful in the darkroom. Other miscellaneous darkroom requirements include boxed gloves, a wastebasket for the disposal of all film wrappings and contaminated gloves, and an x-ray viewbox that is used to examine radiographs.

Waste Management

Developer

Used developer is not typically a hazardous waste. It can be discharged to a sanitary sewer system. Unused developer may be hazardous because of a high pH. Check the material safety data sheet (MSDS) for the pH of the solution. If it is ?12.5, it is considered hazardous. It is important to remember that developer is caustic and should be handled with care. If any question remains, the local sewer authority should be contacted prior to discharging. Never discharge used or unused developer to a septic system.

Fixer

Fixer solutions and rinse waters following fixer baths generally contain silver at concentrations of ?5.0 ppm making them hazardous. Solutions should be run through a silver recovery unit to remove silver. After the silver is removed, the solutions may be discharged to the sanitary sewer system. Recovered silver must be disposed of via an approved waste carrier for recycling or disposal. If a silver recovery unit is not available, a company may be contacted to pick up the
untreated fixer solutions. Store such solutions in labeled containers.
Never discharge the fixer solution into a septic system.

Developed films do not require special handling and may be disposed of along with normal office trash. Undeveloped film packets contain silver and lead; such packets should be collected in an approved waste container. When the container is full, an approved waste carrier or supplier should be contacted for removal. Lead foils may be collected separately in recycling containers that are located in the darkroom. When full, the container should be sent for recycling.