rotary screw compressors use two meshed rotating positive-displacement helical screws to force the gas into a smaller space. these are usually used for continuous operation in commercial and industrial applications and may be either stationary or portable. their application can be from 3 hp (2.24 kw) to over 500 hp (375 kw) and from low pressure to very high pressure (&gt;1200 psi or 8.3 mpa). they are commonly seen with roadside repair crews powering air-tools. this type is also used for many automobile engine superchargers because it is easily matched to the induction capacity of a piston engine.