Abstract: A spray device is disclosed herein comprising a reservoir having a centre; a gas inlet tube configured to introduce a gas from a gas source into the reservoir, the gas inlet tube having a proximal end for fluid connection to the gas source and a distal end within the reservoir; and outlet configured to release fluid from the reservoir, wherein the gas inlet tube is positioned to direct gas entering the reservoir away from the centre of the reservoir. The spray device may be actuated in response to detection of an event by a sensor. The spray device may spray a unique marker liquid.