To burn or not to burn?
That is the question researchers from the University of Wollongong-led Bushfire Risk Management Research Hub have been investigating for months on end.
Today they presented their findings at a conference, explaining why smoke from prescribed burns blankets the Sydney region, at least once a year.
The conference came just days after a hazard reduction burn at Avon Dam over the weekend saw pollution reach "hazardous" levels in parts of the Illawarra on Monday.
Weather conditions resulted in the smoke drifting east and settling around Dapto, Horsley and surrounding areas with a thick haze and smell of smoke visible for much of Monday.
Decisions about when, where and how long to burn are weighed against the potential health dangers from the smoke the fires produce.
Exposure to fine particles (PM 2.5) from smoke can cause a range of health impacts, particularly for people with existing heart and lung conditions.
The NSW Rural Fire Service halted hazard reduction burns in late May after smoke drifted east and blanketed the Sydney Basin.
The Bushfire Hub's first conference included early results from research into fire and smoke behaviour that will improve the accuracy of planning prescribed burns, reducing greenhouse gas emission and human exposure to dangerous particles.
Hub researcher Dr Owen Price said the models used to predict smoke dispersion contained uncertainty, particularly around the actual smoke impact near the fire, and are not well validated against observational data.
"Two key issues are differences in smoke from a wildfire and from a prescribed burn and the accuracy of the smoke dispersion model," Dr Price said.
"Smoke from a prescribe burn can linger near the fire. Given that prescribed burns are often nearer to communities they are intended to protect; we need to better understand the impact of that smoke."
Prior to a planned burn, Dr Price deploys remote sensors up to five kilometres from the fire ground to collect local data about smoke travel, while permanent air quality monitors around the Sydney region provide data about the extent of travel.
"Fire services have a very limited window of opportunity in autumn and spring to conduct hazard reduction burns," he said.
"It's a resource-intensive exercise that takes a lot of planning and the last thing they want is to have to cancel a burn because the smoke has settled over populated areas."
A later stage of the project will track wildfires, to understand the differences in smoke travel between prescribed burns and wildfires.
The Bushfire Hub is a $4 million, five-year project that will provide NSW-centred scientific research needed to ensure the safety of communities, property and the environment.
Tuesday's conference is the first for the Hub, bringing together researchers, fire agencies and land managers to present and discuss the latest research, methods and tools for reducing risk to people and property from bushfires.