Conditions for Australian Open qualifying aren't expected to improve until late Wednesday, with players again set to battle through smoke at Melbourne Park.
On Tuesday, several players complained about conditions, including Australian Bernard Tomic, who sought medical treatment during his first-round loss, where he struggled to breathe at times.
Slovenia's Dalila Jakupovic feared she would pass out, before retiring from her match, when she collapsed to her knees with a coughing fit.
Health authorities expect air quality to bounce between the "very poor to hazardous range" until at least Wednesday afternoon, with a top temperature of 34C, before a late change that brings rain.
Tennis Australia will continue to work with its medical team, the Bureau of Meterology and Environment Protection Authority Victoria scientists, when making decisions about player safety.
TA has installed measuring devices on site for air quality, with play cleared to continue during the opening round of qualifying.
Austrian top seed Dennis Novak is in action against German Dustin Brown, while several local hopes take to the court on day two.
Among the Australian women, Kaylah McPhee takes on Belarussian Greet Minnen, while Jamie Fourlis meets Fang Yin Xun from China.
Olivia Rogowska and Storm Standers are also in first-round action.
In the men's draw, Akira Santillan faces Frenchman Quentin Halys, while Sydney teen Rinky Hijikata has a tough first-up encounter with second-seeded Swiss Henri Laaksonen.
Australia is already guaranteed 18 players in the singles main draws, led by women's world No.1 Ashleigh Barty, with play beginning on Monday.