The use of high pressure water streams to disperse crowds, in general, and to subdue unruly individuals in a prison environment has been shown to be an effective way to reduce the severity of the confrontations among the inmates and guards. The less lethal chemical delivery system (Hydro-Force) disperses chemicals, such as oleoresin capsicum or 'pepper spray' (OC), in the high pressure water
... [Show full abstract] stream. The high pressure water stream is aimed to impact the target individuals. A close miss overhead is still very effective as the water mixture can 'ran' on them and soak the target individuals. The effect of the OC is multiplied by the whole body exposure with excellent results in stopping any undesirable behavior of the target individuals, without bodily contact or struggle with the guards. The possibility of producing blunt trauma damage by the impact of the water stream, at close range, was a concern to be investigated. The water stream can be considered as a special fluid kinetic energy projectile. At impact, the kinetic energy of the mass and velocity of the stream of water is dissipated and its momentum is transferred to the target. The purpose of this cursory study is to evaluate whether the physiological effects of this impact is below the threshold of damage or lethality. Comparisons are made, where the two crucial elements, the force coupled to the target and the duration of its application, in order to establish the probably level of blunt trauma associated with the use of the water jet.