Conditions for the Australian Open qualifying aren't expected to improve until late this evening with players set to again battle through smoke at Melbourne Park.
A number of players complained about the conditions last night, including Australian Bernard Tomic, who sought medical treatment during his first round loss when he struggled to breathe.
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 the air quality to bounce between the "very poor to hazardous range" until at least this afternoon, with a top temperature of 34C before a late change that's set to bring rain.
Tennis Australia says it will continue to work with their medical team, the Bureau of Meterology and Environment Protection Authority Victoria scientists when making decisions about whether it's safe to play.
TA says it has installed measuring devices on-site for air quality, with play cleared to continue during the opening round of qualifying.
Top seed Dennis Novak, from Austria, is in action against German Dustin Brown, while a number of 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.