Emergency warnings were issued for a total of seven bushfires on Thursday as hot westerly winds whipped up blaze after blaze.

By 9pm on Thursday night the Currowan fire north of Batemans Bay, the Three Mile blaze and the Gospers Mountain fire close to Sydney, the Green Wattle Creek fire near Warragamba Dam and the Little L Complex Fire near Wollombi were all still classed as emergency warning fires.

"It's going to be a really long night for a lot of communities and the firefighters in those areas," Deputy Commissioner Rob Rogers told the ABC

"I think the really difficult thing is the amount of fire people have seen since the beginning of August how much fire we've had in the northern part of NSW - well we've just replicated that in the central part of the state as well as still having the north going so it's quite extraordinary conditions."

The 230,000-hectare Gospers Mountain blaze on Sydney's northwestern outskirts was the first fire to go to the emergency level on Thursday and as the day dragged on there were fears the fire would merge with the 6000-hectare Three Mile blaze near Wisemans Ferry.

Gary Flynn from the Wisemans Inn Hotel said the small town was "dead quiet" as bushfires burned across the Hawkesbury River.

"We are just copping all the smoke," he told AAP on Thursday.

"We are just keeping an eye on things at the moment. The town is dead quiet."

Late on Thursday night the Three Mile fire began impacting Mangrove Mountain, spreading quickly in an easterly direction.

Those living in Lower Mangrove, Greengrove, Mangrove Creek and Mangrove Mountain were warned they were at risk and to seek shelter.

Meanwhile the Green Wattle Creek fire, near Warragamba Dam, crossed Lake Burragorang and was spreading east on Thursday night, with residents in Oakdale, Nattai, Werombi and Orangeville advised to seek shelter as the blaze approaches.

Earlier in the day three firefighters were airlifted from the fireground after they were injured while battling the blaze. RFS spokesman Greg Allan said the firies sustained minor injuries only.

On the South Coast between Batemans Bay and Ulladulla, the Currowan fire hit the town of Bawley Point on Thursday with firefighters and residents alike desperately doing what they could to save homes in the coastal town.

A number of buildings were destroyed in the area on Thursday, however its unclear at this stage if homes were among the number.

The Currowan fire had destroyed at least one home near the town of Kioloa earlier in the week.

As the fires continue to rage, the longest period of air pollution on record in NSW is set to continue with the Bureau of Meteorology saying heavy smoke from the bushfires ringing Sydney will linger in the city basin until Saturday.

Sydney's east and southwest were rated as "hazardous" for air pollution on Thursday while northwestern Sydney was between "very poor" and "hazardous".

The lower Hunter and Central Coast also had hazardous air quality.

The environment department says this season's bushfire emergency has caused "some of the highest air pollution ever seen in NSW".

"This event ... is the longest and the most widespread in our records."

Wind gusts of up to 80km/h have been experienced across the ranges with Friday expected to be worse again.

Almost the entire coastal area of NSW and much of the state's northeast have a severe fire danger rating for Friday.

Total fire bans will be in place for the far south coast and the Monaro alpine, southern ranges, Illawarra-Shoalhaven, central ranges, Greater Sydney, Greater Hunter, northern slopes and northwestern regions.

Australian Associated Press