The developed variable pressure HCD ion source and its image are depicted in Figures and (b), respectively. Instead of He or Ar, air has been used as a carrier gas in the HCD ion source to generate the glow discharge. This design may make the HCDI-MS system appropriate for application in public places such as airports, train stations, cultural centers, and other locations for the detection of prohibited chemicals such as explosives, drugs of abuse etc. The use of air as a carrier gas in the HCD ion source eliminates the requirement for reagent gas changes on a regular basis. The HCD ion source was kept running at 5 Torr for a month using air as the carrier gas to test its resilience, and no substantial corrosion inside the electrodes or insulators was visible to the naked eye.