Abstract: A portable leak detector is disclosed for use with, say, helium as a tracer gas. The leak detector includes an improved separation chamber, an air pump for pumping the sample gas, a high vacuum spectrometer, and a small and lightweight evacuation pump. The separation chamber is formed by an air-tight enclosure which has an inlet duct, an outlet duct, and a tubular separation membrane extending between manifolds connected to the ducts. Gas samples are collected by a gas sampling probe and pumped by an air pump into the inlet duct of the separation chamber, through multiple parallel tubes of the tubular membrane material, and out the outlet duct of the separation chamber where it is exhausted. The multiple tubes are formed of a selectively-permeable membrane material such as Tefzel which permits the rapid diffusion of helium therethrough but which has relatively low permeability for other gases contained in the gas sample.

Abstract: A cathodic protection anode may be provided with arrangements for continuously supplying a slightly conductive aqueous solution to the ground above the anode so that the body of earth within which the anode is located is both moist and conductive. Above each anode may be mounted a container which includes rock salt forming a saturated salt water solution, and mixing arrangements for combining the saturated salt solution and fresh water in the desired proportion to form the slightly conductive aqueous solution. A long capillary tube is employed to feed water in very small quantities to the saturated salt solution, and a much shorter capillary tube feeds greater quantities of water to the mixing device so that a metered flow of the saline solution is combined with much larger metered flow of fresh water. The fresh water inlet tube and the insulated conductor for powering the anode may be included within a single plastic conduit extending from a central location to the individual anode structures.

Abstract: A gas leak detection system is provided which includes a large number of small diameter flexible tubes which are mounted in alignment and which extend down close to the surface of the earth or the street where the gas leak is to be detected. The total internal volume of the system is kept to a minimum by using very small diameter tubes and minimizing the volume included in the system. Preferably the total volume in the system is less than 100 cubic centimeters. This provides for a response time of three seconds or less with the small portable ionization type gas detectors which are commercially available. Manifold arrangements are provided which give equal length trasmission paths from all of the sampling tubes. A counterweighted boom is employed to sense leaks beyond the curb adjacent the street where the vehicle is travelling.