Play in Australian Open qualifying is getting underway following a three-hour delay due to smoke from the Victorian bushfires hanging over Melbourne.
Players have begun their round one matches on Wednesday, while others have been out on the practice courts since 11am.
Tournament officials were heavily criticised on Tuesday for allowing play to proceed at Melbourne Park, which forced the mid-match retirement of Slovenia's Dalila Jakupovic with breathing difficulties.
The air quality index at 1pm in the Melbourne CBD on Wednesday showed conditions as "unhealthy", an improvement on Tuesday's "hazardous" reading.
There was no option to move play to the venue's eight indoor courts, excluding the main air-conditioned arenas such as Rod Laver, as there are permanent open vents.
A number of players complained on Tuesday, including Australian Bernard Tomic, who sought medical treatment during his first-round loss when he struggled to breathe.
Tennis Australia said it will continue to work with its medical team and the Bureau of Meteorology and Environment Protection Authority Victoria scientists when making decisions about whether it's safe to play.
TA said it has installed measuring devices on-site for air quality, with play cleared to continue during the opening round of qualifying.
Qualifying top seed Dennis Novak from Austria will be in action against German Dustin Brown, while a number of local hopes take to the court on day two.
Queenslander Akira Santillan is among those first up, taking on Frenchman Quentin Halys.
Health authorities expect the 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's set to bring rain.
