Abstract: A method and apparatus for preventing compressor slugging in a vapor-compression system having an outlet and an inlet connected by a closed loop injects an immiscible charging gas such as nitrogen into the system in an amount sufficient to raise the system pressure by a predetermined amount. The charging gas is separated from the refrigerant and collected in a charging gas separation area of a receiver in the loop. The charging gas remains in the charging gas separation area of the receiver until the power to the compressor system is shut off. A valve in a branch line leading from the charging gas separation area of the receiver automatically opens when the power is lost which releases the charging gas to pressurize the compressor. Pressurization prevents refrigerant in the system from migrating into the compressor to cause slugging when the compressor is reactivated.