Did you spend time outside in Sydney during the smoke haze on Thursday? Were you left with a bad taste in your mouth?

Well, it's no surprise because one respiratory expert believes you 'smoked' the equivalent of up to 32 cigarettes.

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Associate Professor Brian Oliver from the University of Technology, Sydney reached this conclusion after analysing the city's level of smoke-related particulate pollution, otherwise known as PM2.5.

Usually sitting at around eight, the reading, which is supplied by the NSW Department of Environment, was clocked at 641 on Thursday.

And on Tuesday the PM2.5 reading reached 734 in the city's most highly polluted areas, the equivalent of 40 cigarettes.

According to Oliver, when breathing in pollution at this level, it comes with similar long term health effects of smoking dozens of cigarettes.

Thick smoke obscures the Sydney Opera House and Sydney Harbour bridge in Sydney on Thursday, November, 21. Credit: DEAN LEWINS / AAPIMAGE

How they differ is someone who smokes will typically smoke every day, whereas the average non-smoking Australian is not exposed to these levels of pollution on a daily basis.

Oliver says while bushfire smoke is made up of a number of potentially hazardous components, we're most affected by the particulate matter - a complex mixture of extremely small particles and liquid droplets in the air we breathe.

"The particulate matter we're most concerned about are the small particles that can enter our lungs and into our bloodstream, and affect our internal organs," he told The Latest.

Air pollution

More than 60 blazes continue to burn across NSW on Friday and the hazy Sydney conditions are set to stay.

The Bureau of Meteorology say the poor air quality is likely to last through the weekend as bushfire smoke from the north of the state is blown south.

Oliver says these conditions are "as bad as they get".

A man jogs under the Sydney Harbour Bridge as a smoke haze hangs over Sydney. Credit: Rick Rycroft / AP

"The visibility and the air quality index tell us what is obvious to anyone in Sydney today, the levels of pollution from bushfires is extremely high, with hazard warnings for most places in Sydney.

"When the air quality index reaches 200 a hazard warning is issued, and current readings are as high as 750 in inner-city suburbs in Sydney."

The density of the smoke in the city has been deemed poor, meaning it poses a risk to people with heart or lung conditions.

Sydney's smoke haze as seen from a plane window. Credit: NEIL BENNETT / AAPIMAGE

The NSW Environment Department advises, "everyone, especially people with heart or lung disease should avoid outdoor exertion and stay inside as much as possible".

"If you have symptoms rest and use your reliever medicine. If symptoms persist, seek medical advice," a statement said.

Fire conditions

While there are no total fire bans in place for Friday the Rural Fire Service NSW says warm weather is set to continue, with nine regions - including the ACT and entire northern coast - at "very high" fire danger.

The Sydney skyline is seen from Balmain as winds blow smoke from bushfires over the CBD in Sydney. Credit: DYLAN COKER / AAPIMAGE

Greater Sydney is at "high" fire danger but is also grappling with heavy smoke blanketing the city from the nearby Gospers Mountain fire in the Hawkesbury, which has burned through more than 170,000 hectares.

A dust storm coming in from South Australia would also reduce visibility.

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The RFS said haze around Sydney would dissipate throughout the day but NSW air quality indexes on Friday morning deemed Sydney's northwest and southwest regions "hazardous" for air pollution. Sydney's east was deemed between "very poor" and "hazardous" quality.

The Lower and Upper Hunter regions were also enduring hazardous air quality.

"Once again over the weekend, because of northeasterly winds, we could actually see that smoke come in again," RFS spokesperson Ben Shepherd told the Seven Network on Friday morning.

"Until such time that we get a big clearing event, we're going to have this smoke settling over Sydney each and every morning."

- With AAP

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