Personnel monitoring usually performed through use of Film Badges for whole body exposures and TLD ring badges for extremity exposure

• Most popular type of monitoring device  
  

• Contains photographic emulsion mounted in plastic and then over-wrapped in light-tight paper  
  

• Measures whole body exposure  
  

• Distinguishes type of radiation to which wearer is exposed

• Plastic case has cutaway portion to permit entry of b- particles
  

• Contains 3 small metallic filters- usually Cu, Cd, and Al, placed in different portions of case to help distinguish among higher energy photons  
  

• Each metal attenuates photons of different energy values
  

• When radiation is absorbed in film emulsion, some Ag halide grains are altered. These grains, which form the latent image, respond differently to developers and are reduced to Ag metal at much faster rate than unaffected grains. Optical density of Ag is proportional to radiation exposure.
  

• Metal filters reduce photon energy to levels whci are optimal for photographic emulsions.  
  

• Film density is compared to that of films exposed to standard doses of radiation of similar energy to estimate absorbed radiation dose.

Advantages

1. Provides permanent record of individual exposure

2. Relatively inexpensive

3. Requires no technical knowledge of user

4. Film can be re-read at later date

Disadvantages  

1. Takes 3-5 weeks for results  of previous month

2. Not very accurate (qualitative  vs quantitative)

3. Not very sensitive at low  levels (<40 mR)

4. Fair reproducibility

5. Affected by heat, e.g.,  sunlight; ruined by washing  machine cycle

6. Image changes as f(t)-  develop within 1 month