Incorporating: Environmentor BMM-3000 main magnetic field meter with an orthogonal magnetic sensor, a laptop PC and EMCH's broadband/surveillance software. The magnetic field strength in uTesla is recorded every period and plotted against time from the computer clock. Typical applications are where health and safety is concerned over possible levels in vicinities where people work, for example for risk assessments with regard to the EMF directive. Another application is the verification of sporadic rogue magnetic fields which occur for whatever reason but are believed to cause electronic systems failures. Yet further uses are envisaged where the environment needs to be monitored over a period of time before the erection of a building housing sensitive electronic apparatus. Data can be stored over a period of roughly one month. This system is mains driven.