A process for oxygenating organic substrates such as aliphatic hydrocarbons has been developed. A statistical model of the background is built for each pixel, and each pixel in an incoming video frame is compared with the background statistical model for that pixel. The modulating unit modulates the light emitted from the light sources, based on the image acquired by the image acquiring unit. Filter arrangements may take the form of tubular, radially sealing elements; tubular, axial sealing elements; forward flow air cleaners; reverse flow air cleaners; and panel filters.