The Lower Hunter's air quality has again reached hazardous levels with a cocktail of bushfire smoke and sea mist descending on the region in the past few hours.
Wednesday was the eighteenth day that the region has recorded hazardous or very poor air quality since December.
By comparison, the region had one hazardous day for the same period in 2018 and 2017.
Health authorities have renewed calls for people with respiratory conditions to take extra precautions.
Hunter New England Health data shows there were 624 emergency presentations for breathing and asthma related conditions in December, a 25 per cent increase on the five year average.
The Lower Hunter's air quality index was 403 at 2pm on Wednesday.
The index, which is derived from the several different pollutant levels, classifies an air quality index under 66 as good or very good, 66-99 is fair, 100-149 is poor and 150-199 is very poor and 200 and above is hazardous.
The worst day was December 10, which had an air quality index reading of 663 - a figure on par with the world's most polluted cities.
It was followed on December 4 with a reading of 647 and January 1 with a reading of 558.
"The length and the density of the smoke haze to which we're being exposed at the moment is of unprecedented nature," the Australian Medical Association's Dr Tony Bartone said.
"It has been going on for longer and it's particularly thick and poor air quality in our major capital cities."
NSW chief health officer Kerry Chant said NSW Health had issued 15 health warnings since the start of the bushfire emergency and was distributing 1 million P2 masks to bushfire zones.
"To best avoid smoke, stay indoors with windows and doors closed and not undertake outdoor exercise," Dr Chant said.
She said the state's hospitals continued to operate well, despite an increase in emergency presentations for asthma and breathing problems - 1,115, compared with the five-year average of 829, during December 30 to January 5.
Short-term exposure to bushfire smoke or poor air quality are not known to have any long-term health effects and there is evidence to suggest that even after long-term exposure for many years, people's health improves when their exposure is reduced.