The heart of every air conditioner system- automotive air conditioner, home window air conditioner, or central air conditioner-is the compressor. Residential systems use a hermetically sealed compressor unit. Hermetically sealed compressors combine an electric motor and compressor in a single unit. Automotive air conditioning systems use a radial compressor powered by the car engine. The compressor takes in low-pressure gas at its "Inlet," compresses it, and discharges it as a high-pressure gas at its outlet. The pressures involved are different for different refrigerants. For refrigerant R134a, the environmental refrigerants used in modern automotive air conditioners, the suction side pressure is between 25 and 40 psi and the discharge side, the high side, pressure is between 225 and 250 psi.