The Overlap Evaluator iPad app from Hiden Analytical is a reference tool for users of mass spectrometers operating in the fields of vacuum science and vacuum processing, and for advanced researchers using real-time gas analysis systems. The evaluator allows the user to create a mass spectral overview of multiple fragmentation spectra to identify the mass peaks with the least spectral interference, therefore most suited to species monitoring. The app also includes a quick mass peak look up table from a library of common gas and vapor species. Based on proprietary QGA quantitative gas analysis system software, up to 16 gas and vapor species can be added to an analysis setup. Upon adding the gases and vapors of interest, the app automatically provides a simulated analysis and displays the unique mass peaks together with any spectral overlaps. A spectral viewer is included to provide a histogram display of the simulated spectrum of the selected analysis. The concentration levels for each component in the simulation mix can be adjusted to provide a representative simulated mass spectrum of the user’s selected gas and vapor mixture. The app is available free of charge from the Apple app store.