Abstract: A device is provided for irradiating a fluid containing molecules subject to photolytic fission within a conduit, wherein the conduit includes a first opening and a longitudinal axis, the device comprising a valve fluidically connected to the first opening, the valve having a passageway leading to a second opening; a first optical member sealing the second opening; and an electromagnetic radiation (EMR) source positioned relative to the first optical member such that the EMR is directed, preferably along the longitudinal axis, through the first optical member and the passageway and into the conduit when the valve is an open position; wherein the first optical member is constructed from a material which is permeable to the EMR.