Oily rags can raze houses
Rags soaked in linseed oil can spontaneously combust within a few hours if left in a pile.
Fire safety investigator Peter Hallett, who investigated the fire that razed Bob Moorfield's home, has seen the damage this simple oversight can do many times over.
Oil left in a container won't ignite, he said - but if spread in a thin layer on a porous surface such as a cotton cloth, watch out.
The oil's increased surface area promoted rapid oxidisation which produced heat, Mr Hallett said.
"If the heat is trapped in a rag that's heating up and it continues to feed on oxygen then the reaction rate will increase and it can spontaneously ignite."
Sunlight could aid the process by raising the ambient temperature.
There was plenty of evidence from years gone by where rags soaked in linseed oil had spontaneously combusted, he said.
"I went to a fire last year at a rural property in Otorohanga.
"A linseed oil rag had been disposed of and had been sitting out on a wooden bench outside. The owners went away, the rags smouldered away and set fire to the house."
Rags could be kept in an airtight metal container to shut off the oxygen supply, then disposed of. Or they could be dried flat in a single layer, so the heat did not build up, then disposed of.
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