These lifts are operated by fluid pressure and raise the platform typically via power from the use of pressurized hydraulic oil. Slight speed variations are possible due to temperature fluctuations, which can change the viscosity of the hydraulic oil.
These are operated by air pressure and are highly efficient because the supply is made by compressing atmospheric air. Most units require no electricity and can be used in anywhere that air is available. (Many manufacturing warehouses have air supplied throughout for the use of pneumatic tools.) Because there is no hydraulic fluid, there is no potential for line contamination, so these lifts require less maintenance.
These lifts are extended via a power screw or rack and pinion system, both of which transfer radial motion into linear motion. All electric lifts are mechanical. An advantage of mechanical lifts is that the teeth of the gear system inherently prevent slippage.