Hopper Level Indicators afford reliable and ample warning of high level dust buildup in collection hoppers, which cause short-circuiting of emitting electrodes, damage to collecting plates and/or re-intrainment of collected dust. Hopper level indicators are available in both contacting and non-contacting types. It minimizes possibility of power loss in sections of a precipitator because of short circuiting. It prevents re-entrainment of collected dust by alerting personnel to filled hopper condition.