Air quality experts say face masks are unlikely to protect people from the effects of bushfire smoke when they are worn over a long period, an inquiry has heard.
Centre for Air Pollution, Energy and Health Research chief investigator Guy Marks says P2 face masks need to be tight-fitting and replaced regularly because they lose their effectiveness once moist.
"The likelihood that you can protect yourself from fine particles by a well-applied face mask for a long period of time is not that likely," Professor Marks told the NSW parliamentary inquiry into air quality on Friday.
"People are more likely to be protected by staying in an indoor environment with the windows closed but, of course, that is not that feasible for long periods of time."
Prof Marks said the effectiveness of face masks was still being investigated by the centre, particularly for those who are susceptible due to underlying lung conditions.
He said the role of masks in 2020 has been "very interesting", first during the bushfires and then the COVID-19 pandemic.
"In this latter crisis, the role of them is not only in protecting the individual from inhaling things but more importantly, preventing them from expelling things into the environment," the chief investigator said.
"But with the bushfire smoke, that was irrelevant and it's only about protecting the wearer from what's in the environment, and the effectiveness of them for that over a long period of time is dubious."
NSW Health acting executive director Dr Richard Broome told the inquiry the state distributed about 900,000 P2 masks during the crisis but agreed there was limited research about their effectiveness.
"PPE is really at the end of the spectrum and it's for the reason that we really aren't sure how well it works and if it's not working you aren't getting any protection at all," the health protection expert said.
Dr Broome added the state was focused on the development of a national air quality warning system to avoid inconsistency across states and territories.
This is supposed to be implemented by the beginning of the next bushfire season on October 1.
But Department of Planning, Industry and Environment climate director Matthew Riley said COVID-19 had slowed the development of the standardised system.
Environment advocates told the inquiry the state government should implement a clean air strategy to tackle all causes of air pollution in NSW.
Mr Riley said "draft documents have been prepared" after a consultation paper was released in 2016 followed by a clean air summit in 2017.
Environmental Justice Australia campaigner Maxwell Smith told the inquiry research from March 2020 estimated that bushfire smoke was responsible for 219 deaths in NSW.
The inquiry continues.