Residents in Australia woke to another hazy morning on Friday after continued hazard reduction burns led to poor air quality.

This week Sydney and Canberra ranked within the top 20 cities for the worst air quality in the world, 9News reported.

The smoke forced the closure of two major highways connecting Perth and the South West earlier this week, according to ABCNews.

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The Health Department is urging people with pre-existing health conditions such as asthma and other respiratory conditions to stay indoors to protect themselves from the haze.

The Department of Water and Environmental Regulation gave the air quality an "extreme" rating, the highest alert, in the towns of Bunbury and Busselton on Monday, but the quality had improved Tuesday.

Sydney, at the opposite side of the country, was dealing with similar issues as precautionary burns took place in Wollongong and the Blue Mountains, 9News reported. The site also explained that a temperature inversion kept the smoke from rising into the atmosphere.

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A hazard reduction burn, also called a prescribed burn or fuel reduction burn, is a controlled fire deliberately started as a precaution to reduce the severity of future wildfires. Other precautions exist, such as mechanical removal of fuel such as brush and dry vegetation, which is less risky but more expensive, according to ABCNews.

Click through the slideshow to see how locals are dealing with the poor air quality.

The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.