A higher energy form of corona discharge characterized by low frequency bursts or streamers. The simplest type forms between charged, isolated nonconductive surfaces and grounded conductors acting as electrodes. For positive electrode, pre-onset or breakdown streamers are observed and the maximum effective energy is 5–10 mJ,while for negative electrode the maximum effective energy is a few tenths of a mJ. Brush discharges may ignite flammable gas and hybrid mixtures but not dust in air. Brush discharges may also form on nonconductive layers with grounded substrates. These include “transitional brush discharges” which have a greater effective energy than brushes from isolated nonconductors but a smaller effective energy than propagating brushes.