VapourSense is a custom-designed portable quadrupole mass spectrometer (QMS) with a membrane inlet. It is used for analysis of vapour samples in air as well as for residual gas analysis. It is ideal for rapid detection of volatile (VOCs) and semi-volatile (SVOCs) organic compounds. It can operate in harsh environments with rapid setup and automated tuning. VapourSense can be used for laboratory or in-field chemical analysis. Applications include security, environmental, medical and forensic analysis.