A system and method for taking a sample of hydrogen gas and conditioning that sample so that extremely low levels of contamination can be more accurately detected. Initially a sample of hydrogen gas is captured and isolated in a collection chamber. A hydrogen permeable membrane is provided having a first side and a second side. The first side of the hydrogen permeable membrane is exposed to the gas sample held within the collection chamber. The hydrogen gas contained within the gas sample begins to permeate through the hydrogen permeable membrane and exit the collection chamber. This causes the pressure of the gas sample within the collection chamber to decrease. Since contaminants remain in the collection chamber, the concentration of contaminants within the remaining sample increases exponentially. The residual pressure within the collection chamber is measured and converted into a contaminant level reading.