The smoke haze that has covered Brisbane and parts of south-east Queensland for the past three days could persist until Friday, the Bureau of Meteorology (BOM) says.
Hazard-reduction burns have been conducted in north-west Brisbane, with winds blowing the smoke across the region.
Brisbane CBD's average air quality was rated "very poor" yesterday and has fluctuated since Sunday.
The Department of Environment and Science smoke and dust health action level report at 11am showed "very poor" air quality at Deception Bay and Upper Kedron, "poor" in Deagon and "fair" in the CBD, South Brisbane, Cannon Hill and around Wynnum.
At 1pm the air was 11.9 times worse than the World Health Organization's annual air quality guideline value, according to IQAir's monitoring.
By 5pm that had dropped to 4 times worse, and the sky in the CBD had cleared significantly.
BOM senior meteorologist Kimba Wong said smoke could be around until the wind turns easterly.
Queensland Fire and Emergency Services (QFES) said active burning in D'Aguilar National Park near Brookfield finished yesterday at 1pm.
They are continuing to monitor conditions.
However, Brisbane City Council is conducting planned burns at Parkinson Bushland and Tingalpa Creek Reserve.
BOM said light westerly winds were expected to blow smoke towards the city this morning, and later northerly winds may spread it towards the southern suburbs.
"At this stage, we're probably not expecting the winds to turn around more easterly … until about midday on Friday," Ms Wong said.
Ms Wong said the morning conditions had tended to be the peak of haziness with the air generally clearing up throughout the day.
"Once we get the day starting to warm up with the sun coming up, the airflow sort of starts to move around a little bit more and you get slightly better smoke ventilation," she said.
Yesterday, Queensland Parks and Wildlife Service said this period could be one of the last windows for burns to be conducted before the weather deteriorated.
The hazard-reduction burns being completed will hopefully mean that when bushfire season starts in a few months' time, the land will be as prepared as possible.
Smoke could reduce visibility for drivers
Brisbane residents have been urged to take precautions with smoky air conditions continuing to linger around parts of the city.
QFES has advised people from Moreton Bay to the Gold Coast to be aware of the conditions.
It is warning the reduced air quality could cause health issues for some people, while smoke might reduce visibility for people on the roads.
Asthma Australia CEO Michele Goldman said health organisations should be included in planning activities such as controlled burns.
"[We] would like to work together with fire and health authorities to make sure we improve the warning alerts and advice we provide to communities ahead of burns," Ms Goldman said.
Lung Foundation CEO Mark Brooke said people with underlying health issues should stay indoors and limit the amount of exercise they do.
"Make sure that your medications are up to date, particularly if you're someone with asthma or COPD [chronic obstructive pulmonary disease]," Mr Brooke said.
"It's really important that you have your rescue medications with you and have an action plan.
"Tragically bushfire smoke is a leading cause of exacerbation or flare-up for people with respiratory disease."
He said it was important for people with health issues to make sure family and friends were aware in case symptoms worsen.
