Bush fires can cause ‘spotting’ (small ignitions caused by burning bark and twigs blown ahead of the main fire front which evolve into large fires). Spotting can occur hundreds of meters ahead of the fire and has been recorded as far as 30km in extreme conditions. However, the greatest chance of spotting is immediately adjacent to the going fire front.
Venting gas bottle
Preparing for a Fire
In preparing your house and property for a fire season the first step you need to understand is the potential threats.
Understanding the Threat
The CSIRO Division of Building Research carried out forensic reviews in Victoria following the Ash Wednesday fires of 1983 to determine why and how buildings ignite. The research showed that there were three common causes of ignition in order of potential:
1 Embers lodging on combustible material
2 Radiation from the fire
3 Direct flame contact
Most houses are ignited by embers and an ember attack looks like this. Wind-borne embers attack houses before, and many hours after the fire front passes through. Fire fronts only affect houses for several minutes.
Embers gain entry to houses through broken windows or gaps in and around walls or cladding, under roofing next to guttering and ignite contents. Embers also lodge on and ignite horizontal timber decks, steps and window sills. They can be blown up against and ignite timber used for supports, under floor battens, posts and steps. Radiation
Radiant heat can crack windows, allowing embers to enter. Radiation also heats the buildings and contents increasing the risk of ignition by embers or flame. Flame contact
The greatest risk is that of vegetation growing against the house being ignited. There is no evidence of houses spontaneously exploding due to heat from the fire front. Buildings are lost because small fires start inside or next to them.
How close are trees and shrubs to your house?
Also research by the NSW Rural Fire Service suggests that at least 70% of people and property owners are not properly prepared for a fire emergency. This section of the Malua Bay website offers suggestions about what you should consider in preparing for not only a bush fire emergency but any emergency. While we offer observations from local experience gained by our fire crews this section is not an attempt to provide definitive directs. You will need to consider your own special circumstances and prepare your plan accordingly.
There is now a vast body of research on how bush fires interact with houses and out buildings. The South Australian CFS has put out a helpful predicted time line for bush fire attack on a dwelling that is worth contemplating, they say "the attack of a bush fire on a building goes through three stages:
Stage 1: As the fire front approaches
The attack begins when embers, blown ahead of the fire front, reach the building and its surroundings. This ember attack can begin up to an hour or more before the fire front itself arrives.
Stage 2: When the fire front arrives
The second stage occurs when the fire front arrives. Ember attack, radiant heat, flames and smoke are at their maximum. But this only lasts for a few minutes while the fire front passes.
Stage 3: After the fire front passes
After the fire front has passed, embers continue to be blown from burning tree trunks, outbuildings, fence posts, wood heaps and the like. This final stage may last several hours.
Fire times associated with these stages could be
Stage 1 As the fire front approaches ½ - 1 hour
Stage 2 When the fire front arrives 5 – 15 minutes
Stage 3 After the fire front passes 3 – 8 hours
The NSW RFS offer a series of excellent suggestions on knowing your risk that complement the above information.
Simple Things to do to Prepare Your Property
Taking in to account the above research some of the things you should do around your property and this will also help you to understand your risk include potential
• Cut back any overhanging trees or shrubs and dispose of cuttings appropriately
• Check the condition of your roof and replace any damaged or missing tiles
• Non–combustible fences are the most effective at withstanding the intense heat generated by bush fires.
• Clean leaves from the roof, gutters and down pipes and fit quality metal leaf guards.
• Plant trees that are less likely to ignite due to their low oil content.
• If you have a water tank, dam or swimming pool, consider installing a Static Water Supply (SWS) sign.
• Enclose under floor areas
• Store wood piles well away from the house and keep covered.
• Keep garden mulch away from the house and keep grass cut short.
• Make sure the pressure relief valve on LPG cylinders face outwards (so flames are not directed towards the house).
• Ensure you have heat resistant hoses long enough to reach every part of your home.
• Remove and store any flammable items away from the house.
• Install metal fly wire or solid screens to the outside windows and doors.
• Have a non-combustible door mat.
• Check the condition of external walls, cladding and seal any gaps.
The ABC has a very good comprehensive list of additional matters you should consider before a fire front arrives (whether you are staying or leaving) as well as if you are travelling in a fire affected area that you should look at.
At the beginning of winter a couple of quick checks
Check you heater and exhaust fans for build up of dust or lint.
Check where you store your wood - better a bit away from the house structure.