In a method for assessing ambient conditions of an installation site of a magnetic resonance imaging device, various places in an area surrounding said installation site are examined by means of a detection unit for changes in a test magnetic field and the ambient conditions are determined from the results. The detection unit comprises a magnetic field generator and a magnetic field sensor and the examination of each of the places comprises the following method steps: Positioning the detection unit at the place, Generating the test magnetic field by means of the magnetic field generator, Determining changes in the test magnetic field by means of the magnetic field sensor.