An ember attack is when, during a bushfire, embers (also known as firebrands) such as burning twigs, bark fragments, moss or leaves become temporarily airborne and are carried by winds in a cluster.
Fuel characteristics that make plentiful and efficient firebrands are not definitely known. The material needs to be light enough to be carried aloft in updrafts, yet capable of burning for several minutes while being carried forward by the upper winds. Decayed punky material, charcoal, bark, clumps of dry duff, and dry moss are efficient firebrands.[1] Eucalyptus bark is generally considered the most dangerous source in Australia. This led to the definition of a categorical classification (Bark Hazard)[2] used to evaluate the potential threat of ember attack. The Stringybark species of Eucalypt is particularly notorious for contributing large flaming sections of bark that due to their size, weight and shape, can be carried up to several kilometres away. The movements of embers from a bushfire are the primary cause of spot fires, which contribute to the continued spread of a bushfire.