TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: The method includes irradiating the flammable material with UV radiation at the wavelength of 100-290, preferably 240-280 nm. In the method, the fuel vapor is treated in a fluid (air). Preferred Components: The apparatus for connection to a fuel line for treating fuel in the fuel line (aircraft fuel line), comprises: a sleeve made of a material transparent to the UV radiation and a UV light source for irradiating fuel which flows along the fuel line with UV radiation, where the source is arranged to extend axially along the interior of the sleeve and the source and sleeve is mounted at predetermined locations within the fuel line; means defining a mounting for at least one UV light source with associated window means and means defining a duct for channeling fuel flow along the fuel line, where at least one UV light source with associated window means is disposed on one side of the duct outside of the fuel line such that in use of the apparatus the UV radiation from the source irradiates the fuel via the associated window means as the fuel flows along the duct and the associated window means is made of material transparent to the UV radiation; or means defining a mounting for many UV light sources and means defining a duct for channeling fuel flow along the fuel line, where at least one of the UV light sources with associated window means is disposed on one side of the duct outside of the fuel line and another of the UV light sources with associated window means is disposed on the opposing side of the duct outside of the fuel line such that in use of the apparatus the UV radiation from one or more of the sources irradiates the fuel via the associated window means as the fuel flows along the duct. The source is arranged to follow a path which includes a generally U-shaped bend. The source comprises a first and second section for irradiating fuel with UV radiation and the sections are spaced to define a gap. The first and second sections are elongate sections and the gap is located at the U-shaped bend. The sleeve is formed of quartz material. The associated window means is formed of quartz material. The apparatus is mounted at a predetermined location of a surge tank unit, permitting air which carries the flammable material to be treated as the air is allowed to enter the associated fuel tanks of the unit. The apparatus comprises means defining a mounting for at least one UV light source, where the UV light source with associated window means is disposed on one side of the surge tank unit such that in use of the apparatus the UV radiation from the source irradiates air as the airflows along a duct in the tank unit. The UV radiation is directed at a reflective element in the surge tank unit, permitting air to be treated with the radiation reflected by the reflective element. The light source mounting is mounted adjacent and outside of the tank unit. The apparatus is mounted on: a refueling vehicle, where the refueling vehicle is gas pump, a hydrant refueling vehicle or based on a combination of a gas pump and hydrant vehicle. The apparatus is mounted at a predetermined location in a fuel storage vessel/tank.