Earnshaw Medal
Earnshaw 2009 Nominees: Laura Browne, DIT
Ultraviolet Emissions from Compact Fluorescent Lamps
In this study, fifty compact fluorescent lamps (CFLs) were tested using a Bentham DMc 150 spectroradiometer. Spectral irradiances were measured across both the ultraviolet (UV) and visible range. The EU will phase out the sale of incandescent bulbs, beginning in September 2009. The CFL replacements contain mercury, which has emissions in the UV region. In the interest of protecting employees, the EU Artificial Optical Radiation Directive has stipulated that by 2010, the monitoring of artificial optical radiation levels in the workplace, should be legislated by all EU member states. The World Health Organisation recommends a daily exposure limit of 30 J m-2 effective radiation in the UV range.
The main aim of this study was to measure the effective irradiance levels of a selection of bulbs, currently available on the Irish market, and from this, determine the exposure time necessary to reach the recommended limit. The results follow the trend of a similar study conducted by the Health Protection Agency in the UK last year. Both found double enveloped CFLs to have significantly lower UV emissions compared to their single enveloped counterparts.
In parallel to this, a qualitative study of the photopic performance of the CFLs was carried out. Spectral irradiances in the visible range were measured to investigate the Colour Rendering Index and illuminance of CFLs in comparison to incandescent bulbs. On average, the former was found to be significantly reduced, compared to the accepted value for incandescent bulbs. Although illuminance levels of both types of bulbs were found to be similar, there was a stark difference in the spectral distribution of luminous flux.
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