2.2. UVC radiation source
The UVC radiation source was a low-pressure Hg lamp
60 cm in length (UVC Long Life, TUV 15W G 15 T8,
Philips). This lamp produced UVC at a wave length of
253.7 nm. The shorter, and ozone-forming wave length of
185 nm was filtered out by the special glass tubing of the
lamp (Philips web page, www.philips.com, last visited on
3 November 2006) which was fixed inside a locallydesigned
irradiation cabinet (50 50 30 cm). The cabinet
was made of stainless steel, with the front cover made of
glass. The lamp was fixed to the inner side of the cabinet
roof. The exposure stage was fixed 5 cm from the surface of