Ensuring worker safety from toxic levels of air mercury requires accurate and precise hand-held mercury monitors. The Tekran® JITRbug Instrument is designed as a rapid performance assessment tool for hand-held mercury industrial hygiene monitors. The system uses a built-in saturated mercury source to produce mercury test atmospheres of known concentrations. This is used to audit external equipment and confirm accurate response. The JITRbug system is designed to be simple and foolproof to operate, so even untrained workers can readily audit hand-held mercury monitors.