The invention relates to improvements in surface disinfection apparatus and in particular to apparatus which may be used to disinfect wounds using high concentration aqueous ozone. The Apparatus comprises application means for applying the fluid to the surface to be treated, fluid delivery means for delivering the fluid to said application means and catchment means for collecting the fluid after it has been applied to the surface. Fluid return means are provided for removing the fluid from the catchment means and means for creating a vacuum in the fluid return means. The apparatus further comprises a releasable coupling having two engagable parts and comprising a plurality of channels, at least one of which channels is connected to the fluid delivery means when the parts are engaged and at least another of which channels is connected to the fluid return means when the parts are engaged. Each channel comprises valve means which open when the engagable parts are engaged to allow fluid to flow through the coupling and are closed when the engagable parts are disengaged to prevent fluid flow. Pressure monitoring means measure the pressure in the fluid return means, wherein the measured pressure is compared to a plurality of pre-set pressure values to determine the correct functioning of the apparatus. If the measured pressure is lower than a first pre-set pressure value fluid is prevented from being delivered to the application means.L'invention concerne des améliorations apportées à un appareil de désinfection de surface, et en particulier à un appareil qui peut être utilisé pour désinfecter des plaies à l'aide d'ozone aqueuse à concentration élevée. Cet appareil comprend un moyen d'application servant à appliquer le fluide sur la surface à traiter, un moyen de distribution de fluide servant à distribuer ledit fluide sur ledit moyen d'application et un moyen de collecte servant à collecter le fluide après son application sur ladite surface. Le moyen de retour de fluide
