A rough vacuum pump system includes a primary vacuum pump and a secondary vacuum pump. The primary vacuum pump is an oil-free positive displacement pump, and has an inlet opening, an outlet opening, a compression stage between the inlet and outlet openings, and an intermediate gas passageway that connects to a gas flow path running through the compression stage. The secondary vacuum pump is connected to the intermediate gas passageway of the primary vacuum pump. The compression ratio of the primary and secondary vacuum pumps operating in combination is greater than that of the compression ratio of either of the primary and secondary vacuum pumps operating individually. A vacuum apparatus includes a tracer gas detector connected to an inlet of the primary vacuum pump.