DARK ROOM

INTRODUCTION

  • Term “darkroom” overstates the case
  • White light is EXCLUDED.
  • Important place in the radiology department of a hospital, clinic, nursing home or a private x-ray clinic.
  • Is a room where the latent image is processed into visible image by means of chemical processing. Hence also called processing room.

BASIC FUNCTION OF DARK ROOM

• Storage – of unexposed films

• Film processing

• Handling of films

•Loading and unloading the film

CONSTRUCTION

1. LOCATION

  • Centrally located 
  • Close to radiographic room- time saving   
  • Away from hot, damp basement areas.  
  • Serviced by hatches from the adjacent imaging room
  • Accessible in terms of water and power supply
  • Adjoining viewing room

2. SIZE & INSTALLATION

  • Large enough to accommodate all necessary equipments without crowding.
  • Parameters of an ideal dark room-
  • floor space- 100 sq.feet
  • Ceiling height- 11 feet
  • Size can vary depending on the department needs.
  • Safe distance between dry and wet side.
  • Loading bench and processing tank on opposite sides.

3. BUILDING ESSENTIAL

3.1. PROTECTION AGAINST RADIATION

  • Essential-to prevent film fogging
  • Walls being lined by- lead sheet or lead equivalent material
  • 1.5 mm or 1.6 mm lead mostly used.
  • Alternative- solid concrete wall construction- 15cm thick
  • It leads to sufficient work upto 100kV.

3.2 FLOOR

  • non- porous
  • non- slippery
  • chemical resistant
  • stain proof
  • durable & easy maintenance
  • Light colored
  • satisfactory material- 
    • ceramic tiles of porcelain
    • natural clay
    •  Asphalt tiles
  • unsuitable materials- ordinary linoleum and concrete.

3.3 WALLS/CEILING

  • do NOT have to be dark.
  • color judged under safe light illumination- ensure maximum
  • reflection into working surface.
  • covering with chemical resistant materials-special paint, varnish, concrete or ceramic tiles  
  • easy to wipe/clean

4. FLOOR

  • Window avoided
  • Relative humidity maintained- 40-60%,room temp- 18-20 degree Celsius.
  • Ideal solution- good air conditioning system
  • Alternative –extractor fan- creates positive air pressure.

5. ELECTRICAL WIRING

  • Electric shock is dangerous- as close proximity with
  • chemical tanks
  • Water pipes
  • Damp floors
  • Wet fingers
  • Prevention- proper earthing .

6. PASS BOX

  • Designed – to transfer film cassettes to and from the dark room without radiation light entering.
  • Include 2 compartments-
    •     Exposed
    •     unexposed
  • Metallic structures with lead lining- x-ray shielding
  • Typically wall mounted
  • Near film loading bench
  • Include x-ray proof automatic interlocks, closes one door when other is opened.
  • provides temporary storage of loaded cassettes.

7. ENTRANCE

•There are following types of entrance used in dark rooms-

A. Single door-  

  • simplest type of entrance
  • Single door- light tight & radiation proof
  • An inside lock

B. DOUBLE DOOR

  • having 2 doors
  • one leading IN
  • other used for OUT

c. MAZE TYPE

  • elaborate type of entrance
  • NO requirement of door
  • serves as a light trap
  • High cost
  • Large space occupying
  • Rarely used these days.

D. REVOLVING DOOR

  • Occupies very little space
  • convenient light proof access to dark room
  • echo- friendly

8. ILLUMINATION

  • The dark room should have 2 types of illumination-
    • general illumination/white lighting
    • safe light/radiographic illumination

GENERAL ILLUMINATION

  • Inspection & maintenance of cassette and screen
  • Cleaning of work space
  • Servicing of equipment
  • Sited close to ceiling- avoids strong shadow
  • Moderate in intensity
  • Centrally placed
  • More than one switch preferable
  • Identification of such switches is important

SAFE LIGHT

2 types

  direct – distance: 1.2m from working surface

  indirect- distance: 2.1m from floor

  • Provide adequate illumination without fogging films.
  • Have filters of proper colors(red filters can be used for both blue and green sensitive films) •
  • Working distance- not less than 1.2 m.
  • Bulb wattage- d less than 15 watts. I – 25 watt
  • Work quick under it.
  • Not completely safe, prolonged exposure- fogging of films

9. DRY SIDE

•Components comprises of-

  • Loading bench
  • Compartment for cassettes
  • Film bin
  • Storage for reserve film
  • Brackets for film hangers
  • Wastepaper receptacle

10. WET SIDE

  • Processing tank-simplest type has 4 compartments- •   1. developing   2. rinsing   3. fixing   4.washing tank
  •  stainless steel of alloy- generally used material.
  • Processing chemicals
  • 2 stirring paddlers
  • Thermometer
  • Washing tank
  • Dryers

11. FIRE SAFETY

  • Ideally all darkrooms should be provided with fire exits
  • Clearly indicated
  • Left unobstructed at all the times

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