Air pollution levels in Auckland's central city exceeded the safe standard for the first time in 10 years after the SkyCity fire.
A monitoring station on Queen St had an average reading of between 60 to 70 micrograms of particulate matter per cubic metre after the fire, which started yesterday afternoon.
That is 20 per cent higher than the "acceptable" standard of 50mcg per cubic metre.
The reading, which was over 24 hours, was unverified at this stage, said Auckland Council senior specialist Paul Crimmins.
"If confirmed, this would be the first exceedance of the [particulate matter] National Environmental Standard for Air Quality at the Queen St monitoring site in the past decade."
Crimmins said the monitoring station gave an indication of smoke exposure at a fixed point in the city centre. The readings it took depended on how the wind directed the plume of smoke from the fire, he said.
Pollution levels had dropped "significantly" at the monitoring site this afternoon. Outside of the smoke plume, air quality was generally unchanged.
Auckland Emergency Management is encouraging people to stay as far away from the smoke as possible, keeping windows closed and turning off air conditioning.
"While there is no indication that this smoke is more toxic than other fires, all smoke is toxic and people should do their best to avoid it where possible."
Auckland Council's online Air Quality Index (AQI) shows that the pollution levels temporarily rose as high as 250 per cent of the accepted standard in the past 30 hours.
This afternoon, a Queen St reading showed that the city's air quality was 253 AQI. A value of 100 indicates that the standard has been reached.
A graph for the day shows that Auckland's air quality was measured at 42 AQI from midnight and continued to rise to over 200 AQI.
Monthly data shows Auckland's air quality measuring around 30-40 AQI.
Other suburbs in Auckland, including Glen Eden, Penrose, Takapuna, Henderson, Patumahoe and Pakuranga, measure at 20-40 AQI, which is labelled as moderate.
According to an international Air Quality Index, that uses the US EPA Scale, Auckland's AQI is 108, which is "unhealthy for sensitive groups".
In Australia, where bushfires have taken over in New South Wales, air quality measures 134 AQI.
Other cities known for heavy pollution across the world including India Kanpur, measures an "unhealthy" 185 AQI.
Peshawar Pakistan measures at 169 AQI and Beijing, China 195 AQI.
Cities with "hazardous" air quality pollution include Sanjaynagar in India at 338 AQI and Tekirdag in Turkey at 338 AQI.