A sterilisation apparatus comprising: a chamber H having an internal wall an inlet I and outlet O formed through the internal wall a UV light source L disposed within the chamber and a UV-transparent wall T disposed between the UV light source and the internal wall such that fluid flowing between the inlet and outlet is directed around and/or past the UV-transparent wall. The invention comprises an anti-fouling layer disposed upon the UV-transparent wall for reducing the deposit of contaminants from the fluid thereon. Also claimed is a sleeve incorporating the UV-transparent wall with anti-fouling layer for use in the sterilisation apparatus and a method of improving a UV sterilisation apparatus by applying an anti-fouling layer to a UV transparent wall surround a UV light source. Preferably, the anti-fouling layer is formed from a fluoropolymer such as polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP) and/or perfluoroalkoxy alkane (PFA). Furthermore, the anti-fouling layer may be less than 0.05mm thick so as to minimise any adverse effect on UV transmission. In some embodiments the anti-fouling layer is applied as a heat shrink sleeve or powder coating. The apparatus may be used to sterilise water.
