A low pressure mercury gas discharge ultraviolet lamp with a tubular elongate body with two opposing ends, a first end and a second end, which contains a gas filling, and with at least two electric connectors at each end, which are electrically connected to at least one filament being provided at each end. A discharge length is defined between the filaments, in which at least two filaments are provided at each end of the discharge length. The filaments can be individually supplied with electric energy. The at least two filaments at the first end are of different size and different mass, and the at least two filaments at the second end are of different size and different mass.