Abstract: A non-spill gas-liquid contact unit for use in a portable detector device r testing the atmosphere for the presence of hazardous substances. The gas-liquid contact unit includes a tubular chamber for absorber liquid, surmounted by a tubular air chamber removably attached thereto by a fluid tight joint, and a breather tube for drawing environmental air through the absorber liquid. The air chamber possesses an axial gas inlet tube projecting from its lower end for admitting gas from the absorber chamber, and an axial gas outlet tube whose one end projects into the upper end of the air chamber and the other end can be connected to a vacuum pump. The air chamber with its inlet and outlet tubes functions as a lock so that, when the unit is accidentally tilted from the normally vertical position to a horizontal or an inverted position while it is under vacuum, the liquid cannot spill out of the unit and thus nullify the analysis and corrode the vacuum pump.