Ultraviolet control cabinets dissipate real heat from ballasts and ignitors into a largely sealed enclosure. A blinded filter is the usual first cause of a cabinet running hot: airflow falls gradually, so temperature-related faults appear long before anyone suspects the filter. Replace on a routine interval rather than on symptoms. This is the filter mat for the Wedeco LBX1800, supplied in packs of five. The enclosure fan-and-filter unit is a Rittal SK 3327.700, so the mat can be identified and sourced against the Rittal part number as well as ordered here. Wedeco was founded in Herford, Germany in 1976 and is now a Xylem brand.