 Because the electric field decreases as the distance from the conductor increases, it eventually drops below the value needed for ionization, so corona and brush discharges have a limited extent and are localized near the conductor.Like other electric arcs, brush discharges produce ozone gas, which can be noxious to nearby people in an enclosed space and over time can cause embrittlement of some plastics.The ability of an electrical discharge to cause an explosion in flammable atmospheres is measured by the "effective energy" of the discharge.