Mulch Fires

MulchMulch fires are a regular occurrence in the ACT, especially during the warmer months when rainfall is less likely. An indicator of a potential for fire in a mulch pile in the cooler months is when condensing mist comes from vents within the mulch pile. This is a good indicator that the mulch pile needs to be turned over or spread out before the warmer weather arrives.

Spontaneous combustion does occur in mulch piles. It is chemical and biological oxidation of the mulch and combined with heat retention and airflow in the pile can lead to flaming combustion or a fire.

Keeping mulch piles small, (below 3 metres in height), keeping adequate separation between multiple mulch piles and keeping mulch piles moist all adds to an effective fire prevention strategy.

Ensure that your mulch pile is well away from any building or structure. The chances of a mulch pile fire spreading to a building are high

Face the facts

  • Mulch fires occur regularly in the ACT and tie up large amounts of firefighting resources that could be better used elsewhere protecting the Territory.
  • Mulch fires are likely to occur after long periods without rain
  •  Mulch fires are more likely to occur when the temperature is above 30 °C and the humifity is below 30%,
  • Spontaneous combustion within mulch piles occurs due to biological and chemcial oxidation, combined with the retention of heat.
  • Surface fires in mulch piles are nearly always caused by human intervention, and can be malicious or accidental
  • Keep mulch piles moist to reduce the occurrence of fires
  • Try and keep mulch piles below 3M in height and monitor internal pile temperatures
  • If you have multiple mulch piles, try and keep at least 3M separation between each pile to minimize any fires spreading.

Mulch fact sheet [.PDF  368 KB]