This H2FIRST project report, published in April 2015, describes the current commercial state of the art in contamination detection and identifies the technical requirements for implementing a hydrogen contaminant detector (HCD) at a station. The rollout of hydrogen fueling stations, and the fuel cell electric vehicles they support, requires the assurance of high quality hydrogen at the dispensing point. An HCD, defined as a combination of a gas analyzer and the components necessary for fuel stream integration, installed at hydrogen stations is one method for preventing poor quality gas from reaching a fuel cell electric vehicle. This report presents near term engineering requirements for an HCD at a station, describes the results of a market survey of currently available gas analysis technologies, and identifies the gaps between what is currently available and what is required.