Thick smoke causes 'hazardous' air quality levels in Sydney

Much of coastal NSW is experiencing smoke haze on Tuesday after westerly winds pushed smoke toward the coast overnight and this morning.

Smoke has settled over the city of Sydney. It will continue to linger until temperatures rise later in the day.

The Rural Fire Service has noted that NSW is going through the longest and most widespread period of poor air quality in recorded history, worse than the 1994 Sydney bushfires and the Black Christmas fires in 2001/02.

Sydney has broken records for hazardous air pollution. Of the 25 days from November 11 to December 6, 17 registered hazardous air quality.

Sydney Airport said poor visibility is causing delays of up to 30 minutes, but said no flights have been cancelled. The airport is urging passengers to check with their airlines for further information.

A smoke alarm went off in the airport due to the smoke, but there were no evacuations and no further delays or cancellations as a result, a spokesman for the airport said.

Bushfire smoke is also seeping into office buildings in the city and beyond causing smoke alarms to go off and prompting evacuations - including at the Rural Fire Service HQ and the Sydney Morning Herald.

Severe fire danger is forecast the Greater Sydney, Illawarra/Shoalhaven and Hunter regions.

Firefighters are preparing to tackle high temperatures and windy conditions this afternoon.

A total fire is also in place across the region.

People with heart or lung disease, breathing issues, older adults, and children should avoid exercising outdoors and stay inside.

The advice is to rest and use reliever medicine if you get smoke-related symptoms and if they persist, seek medical advice.

The smoke is expected to linger until later in the day.

The worst air quality is in south-west Sydney, north-west Sydney and the Central Coast.