Turbine powered helicopters use bleed air for heating, demisting and other systems like sand filters. Bleed air is taken from the compressor section of the engine. For example, the Arriel 1 series engines use a two stage compressor section.
The first stage uses an axial compressor to increase the speed and pressure of the ambient air.
The second stage uses a centrifugal compressor to further compress the air and raise the temperature. This is where bleed air is taken from the engine.
Prior to entering the combustion chamber the air is extremely hot from compression alone. For cabin heating, the bleed air is mixed with outside air to cool it.