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March, 2016

Forest Fires and Chainsaws - Discussion document

New Zealand has experienced a number of forest fires over recent years where chainsaws may be the ignition source.  There has been talk that one factor may be that newer, high compression, lower emission chainsaws are running hotter, and this may cause fires.  Tests undertaken on chainsaws indicate this is not likely to be a factor.

A new model chainsaw was tested and found to operate at lower than 50% of international maximum operating temperature standards, so “new chainsaws running hotter” is not the cause.

A possible cause of some forest fires might be how and where the chainsaw is operated in the workplace.  Chainsaws are inherently at risk of starting forest fires.  Even older models.  If used incorrectly, any chainsaw is a potential ignition source.


A forest fire last year prompted me to enquire amongst colleagues, rural fire interests and forest owners and managers around New Zealand whether others have had similar experiences of fires in commercial forests where chainsaws are involved.

My email generated several responses exampling fire incidents involving chainsaws.

My original enquiry email was altered/edited in a manner that changed the enquiry, including changing the email title to include naming a particular chainsaw make and model and suggesting there was an operating issue/risk with this particular saw/model.  This statement is incorrect.  The chainsaw involved at one fire was tested and proven to meet current international standards for performance and operation.  There is no evidence this make and model of chainsaw is linked to the cause of the fire ignition.

Chainsaw Operating Standards

There are two international performance standards for chainsaws:

  • ISO 9467; and
  • San Dimas SAE J335.

Both standards are recognised by forestry internationally, including NZ.  Standards include maximum allowable temperatures, measured at set locations relative to the chainsaw, exhaust port and muffler.  Exhaust temperature comparative tests between a newer, high compression, lower emission chainsaw and an older version of the equivalent model indicated the new chainsaw may operate at as low as 10% higher temperature than the older version – statistically insignificant.

The new, high compression low emission chainsaw we tested operated at temperatures of less than 50% of international maximum temperature standards.

Work methods

There are a number of forest fires during recent years where chainsaws are probably the source of ignition.

Chainsaws are an ignition risk.  A hot chainsaw placed on dry fine fuels can ignite a fire.  An operating chainsaw contacting fully cured fine fuels while being used may ignite a fire.  An operating chainsaw held in one position for even a short period of time may cause an ignition, either from direct contact or when dry fine fuels are in close proximity to the exhaust discharge.  The exhaust discharge from a 30 year old chainsaw is still hot enough at 50 mm beyond the exhaust port to cause ignition.

40 years ago chainsaw exhausts were generally mounted behind the chain bar cover and expelled downwards when the saw was used to fell trees.  This was recognised as a source of fire ignitions so chainsaw manufacturers changed the set-up so exhausts were front mounted.  A key operating practise after that was to maintain a clear area ‘in front’ of the saw.  Good practices such as pre-trimming, workspace clearing of flammable vegetation and placing saws on mineral earth were adopted.

Other good habits when using chainsaws in forestry may include switching work sites to lower risk areas, maintaining good monitoring habits, and if an ignition should occur, having procedures and resources in place to deal with these, including having water on site and an appropriate method of water use (knapsacks, pumps).

Forest Owners Advice

The primary responsibility for risk management in forests lies with the forest owner.  Forest owners are also reliant on their forest managers and contractors to reduce all risks of fire in forests to an acceptable level, and have appropriate preparedness procedures in place in case of fire.

Several Rural Fire Authorities have established guidelines and suggested risk reduction strategies for forest owners, managers and contractors to apply, use, adapt and modify to meet their own requirements for operational objectives and risk management.  Forest owners are advised to contact their local RFA to discuss these.

RFA guidelines are open to interpretation, and are prompts for prudent forest management decision-making.  It is not for fire authorities to manage forest operations.  Any punitive actions by a fire authority affecting forest operations would need to be based on very strong reasoning and justification.  Before that situation arose, a prudent forest owner/manager should already be applying reduction measures.

What we do as the local fire authority is provide guideline trigger points and suggested actions.  If a trigger is reached, a forest manager should take appropriate actions to minimise their risks.  Restrictions on chainsaw use may mean controlling or stopping thinning to waste, moving crews into lower risk blocks (grazed, grass understory), starting and finishing earlier, extra patrols, staying on site for a time after operations cease….whatever a prudent manager decides is the best actions to reduce risk to an acceptable level.  There are many actions managers can and should take depending on the situation and prevailing conditions.

Phill Wishnowsky, Principal Rural Fire Officer, Wairarapa Rural Fire Dsitrict.
Ph (06) 370 9557; Mob 0272 899 609, email

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