Fires around Sydney escalate to emergency level creating fears of them merging into mega blaze

The NSW bushfire crisis has escalated with emergency warnings issued for seven separate fires across the state on Thursday afternoon, as air quality deteriorates to well above hazardous levels in many regions including Sydney.

NSW Rural Fire Service is facing one of its most challenging days of the disastrous season with fears that some fires may merge to create a mega blaze northwest of Sydney.

Strong westerly winds have been fanning the 230,000-hectare Gospers Mountain fire which could merge with the 6000-hectare Three Mile blaze near Wisemans Ferry. Both were at emergency level on Thursday afternoon.

The NSW Rural Fire Service says it's too late to leave for residents in Colo Heights and Boree. They've been told to seek shelter as the Gospers Mountain fire approaches.

Emergency alerts were also issued on Thursday afternoon for the Yengo National Park fire near Singleton; at Currowan near Batemans Bay on the south coast; Green Wattle Creek near Warragamba Dam; at Palerang near Queanbeyan; and at Bangala Creek near Tenterfield.

Firies battle a blaze near Stanford Merthyr, west of Newcastle. Source: AAP

100 fires burning across NSW

Gary Flynn from the Wisemans Inn Hotel says the small town is "dead quiet" as bushfires burn a kilometre away 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. It's a different story for the poor buggers across the river."

The fire service says there are dangerous fire conditions across the state.

"Today will be a long and challenging day," the RFS said in a statement.

"High temperatures and strong winds will make conditions dangerous at many of the 100-plus fires burning across NSW."

The Currowan fire burns near Termeil. Source: AAP

A team of 21 fire management specialists arrived in Sydney from Canada on Thursday to help tackle the ongoing bushfire crisis.

Six fires were at a "watch and act" alert level on Thursday afternoon from near Braidwood all the way up to Port Macquarie.

Heavy smoke to blanket Sydney until Saturday

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

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 northwest Sydney was between "very poor" and "hazardous".

Kings Cross and the Sydney CBD blanketed by smoke haze on Monday. Source: AAP

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".

"Recently NSW has experienced elevated levels of pollutants as a result of smoke from the bushfire emergency and dust caused by the severe drought," a spokesman said.

"NSW has experienced other periods of poor air quality that lasted several weeks, including the 1994 Sydney bushfires and the Black Christmas bushfires of December 2001 to January 2002.

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

RFS volunteers and NSW firefighters fight a blaze near Termeil. Source: AAP

Total fire bans in place in most regions

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 are in place for the far south coast and the Monaro alpine, southern ranges, Illawarra-Shoalhaven, central ranges, Greater Sydney, Greater Hunter, northern slopes and north western regions.

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