Movements in the surroundings produce disturbances by altering the ambient electrical fields. ECG may contaminate the recording. Sweating produces electrical disturbances by shorting electrode pairs. Other sources of artifacts include ambient electrical waves from respirators, intravenous pump machines, televisions, and other electrical equipment. Many are recognized by their characteristic appearance on the tracing, but others are identified by direct inspection and reported by the technologist or identified on the video tracing in video-EEG recording.
Artifacts show great variation because of their protean origin.
The specifics of each are not reviewed here because of their variability. Sweating produces very slow waves, because the salt solution shorts out pairs of adjacent electrodes. Eye movements occur with blinking and result from the electrical charge of the eye itself. They are frontal. Nystagmus also produces artifactual waves.