Abstract: An ozone generator (1) comprises an ultra-violet lamp (2), means (3, 12, 13) for directing a flow of an oxygen containing gas through a zone (16) in which the gas is exposed to ultra-violet radiator emanating from the lamp, and means (8, 9) to expose the gas to a high voltage, low current electric field prior to or during exposure to ultra-violet radiation. Preferably at least one magnet 15 is associated with lamp 2 so that ionized particles within the lamp are concentrated by a magnetic field to congregate in a localized region in the vicinity of the zone (16).