Packaging machine for packaging products in plastic packaging having at least one sealing station for receiving a plastic packaging to be sealed in a reception region within the sealing station. The packaging machine includes a supply line capable to supply a gas to the reception region, a discharge line capable to discharge a gas from the reception region. A valve may be disposed in the discharge line. Further, a vacuum pump may be connected to the discharge line to pump gas out of the reception region through the discharge line valve. A measuring line may be connected to the reception region at a connection point and may be connected to the discharge line in a region between the valve and the vacuum pump via a connecting line. A first shut-off valve may disposed in the connecting line and a second shut-off valve may be disposed in the measuring line.