Helium leak detector

Helium leak detector comprising;

• a gas analyzer, a dry primary pump, a secondary pump connected in series with said primary pump and comprising at least on a discharge side thereof, a Holweck type stage, said secondary pump comprising means for reducing the suction pressure to a value at least equal to 10.sup.-4 mbar and having a discharge pressure compatible with a suction pressure of said dry primary pump, said dry primary pump comprising at least two stages in series, said secondary pump being connected to a low-pressure output of a sampling unit at an intermediate point on said secondary pump where the flow conditions are molecular, a sniffer probe being connected to a high-pressure side of said sampling unit, and said high-pressure side being further connected to said dry primary pump at a point between said at least two stages thereof, whereby said helium leak detector has a very high level of sensitivity, as well as a very short period of recovery when helium pollution of the detector occurs during a previous inspection of a container having a leak.