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).