Green or damp hay encourages elements like bacteria and fungi to grow and decompose.
A series of complex biological and chemical reactions can then cause a build-up that allows hay to heat.
This can produce flammable gasses which may ignite.
The Country Fire Authority warns of the dangers of spontaneous ignition causing hay fires this spring.
Haystack fires are also caused by sparks from machinery and equipment, and embers from burn-offs or bushfires.
To prevent haystack fires the CFA recommends:
Ensure hay is fully cured before baling.
Know the history of the hay you purchase.
Keep haystacks to a limited size.
Store hay in separate stacks, in a number of places away from key assets and away from possible sources of ignition (roadsides, powerlines, workshops and vegetation).
Never store vehicles, machinery and equipment in your hayshed — there is increased risk of losing both hay and machinery.
Store hay in areas that are not likely to flood and in sheds that are in good repair to minimise the moisture content.
Farmers can also consider using temporary fencing to allow stock to graze close to hay and silage stores to reduce fuel loads near these assets.
They are also warned to avoid stacking hay right to the top of a hay shed. Allow some air to circulate at the top — this helps to carry away moisture.
Prevent the ingress of water to haysheds from leaking roofs and spouts.
A moisture meter can be used to monitor hay condition.
The moisture content should be no more than 20 per cent (12 to 18 per cent is recommended as a precaution).
If hay gets too hot:
Spread out the stack to allow the hay to cool.
Don’t walk on top of hay that is heating as it may collapse or ignite. Have your local fire brigade in attendance when pulling apart a hot haystack.
Don’t feed to animals. The heating process reduces the nutrient quality of the hay.
Hay cutting and carting equipment should have protected exhaust systems, a spark shield or the exhaust should be located under the body of the vehicle so emissions are away from the hay.