UV Light Validation


UV lamp used in Laminar air flow and pass box are for germicide activity of that environment.

UV Light Validation

UV light validation to be done to check its germicidal activity. It is validated by exposing plates containing viable microorganisms for different time intervals.

Validation conducted with 200 to 250 microorganisms per plate. These plates shall be exposed to UV lamp at defined places on the working platform  for the given time intervals:

Time intervals

  • One minute
  • Two minutes
  • Five minutes
  • Ten minutes
  • Fifteen minutes
  • Thirty minutes


  • Prepare cell suspension of Bacillus subtilis containing approximately 1000 cells / ml.
  • Prepare Soyabean casein digest agar plates as per respective Standard testing procedure No.
  • Using sterile glass spreader, spread 0.25 ml of cell suspension on the surface of Soyabean casein digest agar plates.
  • Expose these plates under UV lamp as shown in fig.1 for defined time interval.
  • After exposure, cover the plates with lid and incubate at 37°C for 3 days.
  • Repeat the test for each time interval.
  • Keep one un-inoculated plate as negative control and one plate, which is inoculated but not, exposed to UV, as positive control.
  • From positive control evaluate No. of colony forming units as “Initial count”.
  • Count the No. of colony forming units for each exposed plate.
  • Calculate reduction in count after UV exposure

Figure 1



There should be 99 % reduction in the viable count after UV exposure for 30 minutes.

Related Article:

Ultra Violet Light – Role & Application in Pharmaceuticals  


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