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Occupational Exposure to Black Lights

 The Occupational Exposure to Ultraviolet Radiation (2006), Radiation Protection Series No 12, sets out guidelines for the exposure limits to ultraviolet radiation.

The exposure limit values in this standard refer to ultraviolet radiation in the spectral region between 180nm and 400nm and represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effect.

 For the near-ultraviolet UV-A spectral region (315-400 nm), the total radiant exposure incident upon the unprotected eye should not exceed 1.0 J cm-2 (10 kJ m-2) within an 8-h period and the total 8-h radiant exposure incident upon the unprotected skin should not exceed 2.7×105 J/m-2 (Wavelength 365nm, mercury discharge spectrum).

The minimum output required by numerous Australian Standards for Non Destructive Testing is10w/m-2 @38cm.

 This is equivalent to 10 Joules/second   (1 Joule = 1 watt/second)

  •  For Unprotected Eye, exposure limit would occur in 16.66 minutes.
  •  For Unprotected Skin, exposure limit would occur in 7.5 hours.

 Numerous systems with outputs above 60w/m2 @ 38cm are currently available.

 This is equivalent to 60 Joules/second          

  •  For Unprotected Eye, exposure limit would occur in 2.7 minutes.
  •  For Unprotected Skin, exposure limit would occur in 1.25 hours.

 (Note: Times are based on the figures and a distance of 38cm , variations in exposure distance will vary output and times accordingly.)

Safety Precautions:

  •  Never look directly at a lamp whilst it is operating.
  •  Never operate a lamp with a cracked or damaged filter.
  •  Glasses specifically designed to filter black light should be worn, however the transmission curves of the glasses should be checked against the emission curve of the fluorescent material under inspection.
  •  Wear opaque gloves and protective clothing during inspections to protect from possible UV irritation.
  •  Ensure black light source is placed  to minimize direct exposure to operators.
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  1. StuR
    April 10, 2012 at 12:35 am

    Thanks for these details, UV exposure rarely rates a mention in standards or even in past courses. It’s good to see some quantitative treatment of the issue.
    It would be interesting to know how effective typical protective glasses are, and how that affects exposure time?

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