Hazardous Atmospheres

At a chemical fire or spill, chemicals and/or smoke can be released into the air at concentrations which may cause serious health effects by inhalation or skin contact. A hazardous chemical can be a solid, liquid or gas. You might not be able to see or smell anything because many gases are colourless and odourless.

A hazardous atmosphere may occur in residential areas close to industry as the result of a fire, explosion or a chemical spill, or from a road or train transport accident.

A chemical or smoke cloud can be carried downwind as a plume that expands and is diluted by clean air as it travels. The concern with the plume is that the airborne concentration can initially be very high and the contaminants in the plume may cause injury if they are inhaled.

The first indication may be from a strong chemical odour, or you may see a dense smoke cloud in your area. Large industry may activate warning sirens; residences close to some large industries will have previously received information on sirens.

Victoria Police or other emergency services may try and contact people who may be affected by the released chemical using a telephone message or SMS and/or information provided through the media.

The best way to protect yourself and others from harmful chemicals or smoke in the air is to go indoors immediately. This is called shelter-in-place. Emergency officials may tell you to shelter-in-place during a chemical release instead of evacuating. This will avoid exposure to the high outdoor concentration of a chemical.

Sheltering indoors works because the outdoor air does not mix quickly with the indoor air when the building is closed. The fresh air inside a building proves protection for several hours while the hazardous plume is carried downwind and is diluted by clean air.

To maintain the fresh air inside the building before the plume arrives, it is important to implement shelter-in-place immediately (see how to shelter-in-place below) when instructed. This will minimise exposure to toxic vapours and smoke.

It is necessary to consider that all buildings have small gaps and cracks, and some have air vents and chimneys. Some of the harmful vapours in the outside air will gradually infiltrate through these openings into the shelter. Eventually, sometime after the highest concentration of the hazardous plume has passed the shelter, outside air will be cleaner that the air inside the shelter. Sophisticated software allows emergency responders to calculate this time point. They will then issue instructions to ventilate the shelter and building and go outside or leave the area. For this reason, it is very important to promptly leave the shelter when advised to do so, to avoid continued exposure. Hazardous vapours that might have infiltrated the building will eventually dissipate.

Most chemicals can be identified by smell well before the concentration is at high enough levels to cause any harm. If the chemical can be detected inside the house before closing the external doors and windows, it is generally still safer to shelter-in-place rather than attempt to evacuate outside into the toxic plume.

Do not collect your children at school. The schools will protect your children by evacuating or sheltering them in place.

In the event of an emergency, you should tune into your emergency broadcasters: local ABC and commercial radio stations or Sky News TV, where regular programming will be interrupted to provide detailed area specific emergency instructions and more up to date information at regular time intervals.

The Fire Services work in close conjunction with local government, other emergency services and radio stations in the delivery of emergency instructions and up to date information. Television stations will likely provide special bulletins or you can visit the CFA website.