BSOH makes available a few web apps 

• CO2sim: a model to simulate carbon dioxide concentrations over time as a function of human occupancy and local and ventilation parameters
• CO2ana: a model to analyze measured carbon dioxide concentrations in time as a function of human occupancy and local parameters (with a view to deriving ventilation parameters)
• BWStat v3: a handy application for processing measurement data according to EN689, the "BOHS/NVvA Sampling Strategy Guidance" and much more...