Asbestos-containing materials (ACMs) commonly found in domestic buildings are non-friable (bonded) products such as floor tiles, flat fibre cement sheeting (fibro) used in walls and ceilings, and corrugated roofing and fences.
When ACMs are exposed to fire and high temperatures, they may suddenly crack and break, causing the bond to degrade as a result of loss of moisture. In these circumstances, the ACM may ‘explode’ or break into small chips, flakes or splinters, which usually occurs in the early stages of a fire. While this can cause the release of fibres, however these concentrations are well below typical background levels (all air has a low level of asbestos fibres).
Asbestos hazards when returning home after a bushfire - Service NSW
To cause a health risk asbestos fibres must be of a sufficiently small size and inhaled in sufficient quantities to cause a risk to human health.
Analysis of dust, debris and airborne fibres after a fire has been extinguished has found that although bundles of asbestos fibres are present within the debris and ash, there is little evidence of loose, respirable-sized asbestos fibres beyond typical background levels.
Following a fire, control of the site will usually return to the owner or manager of the building. A preliminary assessment should be conducted that focusses on preventing disturbance of the damaged building that may result in further damage and release of asbestos fibres.
The assessment should include the:
- likelihood of asbestos being present (eg building age)
- type and location of ACMs within the building
- extent of damage to ACMs and area over which they are located
- likelihood of disturbance to the affected area by other people or vehicles.
While there is a very low likelihood of asbestos fibres being blown off-site in measurable concentrations to cause exposure the presence of fire-damaged ACMs in the debris zone can cause anxiety to people living nearby. Therefore it is recommended that encapsulation or wetting of damaged ACMs should take place (wearing appropriate Personal Protective Equipment) as follows:
- encapsulate by low pressure spray canister or airless spraying equipment, using products such as PVA glue mixed to a consistency of 5 parts water to 1 part PVA, or
- keep moist with gentle spraying of water, or
- wet down with water (gentle spray), then cover with tarps or similar and firmly secure.
Put up warning signs cautioning people from entering the boundaries of the property. An existing fence around the property boundary may be used to affix them. If signage is not sufficient to keep people out of the debris zone, consider erecting a fence (which can include temporary fencing).
Clean-up or demolition of a fire damaged building must be done safely to ensure the level of asbestos fibres in the air is kept very low. It is recommended that a licensed asbestos removalist is engaged to do the clean-up work.