Fires and smoke

Fires can expose people to a range of hazardous substances. In fact, every major fire is a chemical incident. The size and scale of fire events vary greatly, and the consequences of these releases are also variable. The longer a fire burns, the more products of combustion are formed.

Fires can pose a substantial threat because:

• They release chemicals into the air that may disperse at concentrations well above background levels
• New chemicals can be formed as a result of combustion
• The dispersion of fire-fighting water can cause material from the fire to enter waterways
• The density of people increases in an urban environment.

There may also be intense local deposition of material from the fire, including parts of the structure of the impacted buildings.

In cases of fires in the urban and built environment, public health officers in the National Public Health Service within Health New Zealand | Te Whatu Ora (NPHS) may be involved if there are risks to public health.

The NPHS may be asked for advice on environmental sampling during and after fires, as well as advice on other health-related matters such as evacuation and sheltering. This advice is incident-specific because the combustion products produced will vary depending on the chemicals and materials present and the temperature of the fire, as well as the numbers and vulnerabilities of people who may be exposed (for example, children, older people).

Wildfires produce a large amount of smoke that disperses widely and can affect populations far from the fire source. They can expose people to a range of hazardous substances. In fact, every major fire is a chemical incident. The longer a fire burns, the more products of combustion are formed. The effect of these products on water quality is influenced by, among other things, the fire’s intensity, severity and duration. Changes in the quality of surface waters are greatest immediately after the fire.

In addition to the obvious risks from burning, wildfires can pose a substantial threat because they release smoke, gases and ash into the air that may be hazardous downwind, through inhalation or being deposited in roof or surface water catchments. Further, the dispersion of firefighting water can cause material from the fire and firefighting chemicals to enter waterways. In some instances, hazardous materials (such as asbestos in roofs and agrichemicals stored in barns and rural industrial sites) may be in the pathway of the wildfire and may contaminate land, air or water.

The NPHS is involved in wildfire responses if the fires put public health at risk. For example, people may ask public health officers for advice on health-related matters such as evacuation and sheltering (that is, staying at home if the conditions are safe to do so), as well as temporary cessation of outdoor public activities (such as concerts or sports).

If you are in an area where you can see or smell smoke or have received an emergency alert, you should:   

• Follow the advice of emergency services and leave the area if this is required.
• If you are safe to stay in the area, remain indoors and shut your windows and doors.
• Turn off your air conditioning or switch to ‘recirculate’.
• Keep pets inside with clean water and food and keep pets' bedding inside if possible.
• Disconnect your downpipe if it connects to a water tank – this is important if there is a risk of water contamination from airborne ash, debris or fire retardants from firefighting.   

Smoke inhalation can be particularly dangerous for certain groups, including:    

• elderly or pregnant people
• young children
• those with a heart or lung condition, such as asthma or heart disease.

It is important you stay indoors with windows and doors shut until the smoke has cleared.   

If your drinking water comes from tanks, not council supply

• If you are not on council water supply, you will need to check your roof and rainwater storage tanks for ash, debris, fire retardants or foam. 
• Contaminated water runoff after fires might impact streams, rivers, lakes and groundwater supplies. Test water supplies if impacted by runoff.
• You should disconnect the downpipe to the water tanks if you see any evidence of ash, debris, retardants or foam.
• If you find ash in your water tank or the water has an unusual taste, odour or appearance (possibly a sign of retardants or form), don’t use the water for drinking, food preparation, cleaning teeth or washing, or for pets.
• Disinfecting or boiling the water will not remove ash, retardants or foam.
• Use bottled water or water saved prior to the fire.
• Do not reconnect the downpipe until a good flush of rain has cleaned the roof or until the roof is cleaned manually.
• Contaminated water can be used to flush toilets and water gardens. Do not use on fruit and vegetable gardens.

Food safety  

• Wash home grown fruit and vegetables before consumption with safe drinking water.

Health and cleaning advice if your home or property smells of smoke

• Open windows and doors to bring in fresh air.
• During clean up, wear an N95 or P2 mask if you have one (from a hardware or health/safety shop), otherwise wear a surgical mask. Wear rubber or latex gloves, long-sleeved shirt and pants or overalls.

Internal surfaces

• If you have a respiratory illness like asthma or bronchitis, you may wish to stay away from your house until it has been cleaned.
• Wash your hands regularly, particularly after clean-up and before eating.
• Wash hard surfaces, food preparation areas and any cooking utensils left out using hot water and detergent.
• Clean air conditioning unit filters or ventilation systems, or ask your property manager to do this.
• Wipe any visible soot or dust (e.g. on windowsills) using a damp cloth or mop with mild soap or detergent.
• Vacuum clean carpets and upholstery, preferably using a vacuum cleaner with a HEPA filter.
• If your home has been heavily contaminated with ash, soot or smoke, consider using a professional cleaner. Check your insurance policy covers smoke damage and clean up by contacting your insurance company.
• Children should not be involved in any clean-up.

Outdoor areas  

• If soot or dust from the fire has reached your home, you may wish to hose down your roof, exterior walls, and outdoor surfaces.
• Remove large pieces of debris with gloves, ensuring the debris is cool before placing it in the bin.
• Clean filters and covers of outdoor pools.

If clothing was left on the washing line and exposed to smoke, rewash the clothes. Also, wash any other items that smell of smoke or soot.

Fire and Emergency New Zealand has more information about restoring your property after a fire.

Restoring your property – Fire and Emergency New Zealand (external link)

Asbestos spread from a fire

Fires in older buildings can release asbestos fibres into the air. These may spread to nearby properties through ash or debris.

If you are alerted to asbestos contamination in your neighbourhood, please take care to avoid asbestos. The risk from asbestos is from breathing it in, not from swallowing it or absorbing it through skin.

You may need to have any ash or debris on your property from the fire checked by a certified asbestos assessor. They will advise if you need a certified removalist to help with safe clean up and removal.

Talk to your insurance company about the costs of assessment and removal,  if you are concerned about asbestos contamination from a fire.

Stay out of the smoke plume and inside if possible, to avoid breathing in any fibres.

• Wear an N95, P2 or disposable mask over your mouth and nose when outside.
• Remove your footwear before entering the house.
• Ensure children or pets don’t pick up any debris outside. Keep pets inside so they don’t track asbestos fibres inside your house on fur.

More information about asbestos

Learn about asbestos and your health, what to do if you think you have asbestos in your home, and how to deal with it.

Asbestos (internal link)

Asbestos spread from fire or earthquakes (internal link)

Lithium-ion battery fires

Lithium-ion batteries in electric vehicles (EVs), e-bikes, e-scooters and a range of devices with chargeable batteries can catch fire or explode. These fires produce gases more hazardous than smoke.

These fires are highly toxic, often releasing large quantities of poisonous vapour within seconds.

One particularly dangerous chemical from lithium-ion fires is hydrogen fluoride, which can cause skin burns and lung damage if there is skin exposure or inhalation. Anyone directly exposed to these gases should seek medical attention immediately.

Some of the gases are also combustible and the fires can be challenging to extinguish.

If your battery has ignited

• Call 111 and follow FENZ advice: Lithium-ion battery safety – Fire and Emergency New Zealand (external link)
• Evacuate the area and close doors (if safe) to slow the spread of fire.
• Ensure no one goes back inside the building for any reason.
• If anyone has been exposed to battery fluids, debris, smoke, vapours, or flames, seek urgent medical assistance.
• Burns should immediately be treated with cool running water for 20 minutes and may require emergency care.