Victoria's bushfire emergency has seen smoke shroud the state's second biggest city over the past 24 hours.
Geelong and Collingwood play the first of 18 games in 18 day when the NAB Challenge begins at Simonds Stadium.
Conditions had eased on Wednesday morning.
AFL chief medical officer Dr Hugh Seward, who's based in the region, said it was simply something for players and fans to be aware of.
"Yesterday, certainly there was a very heavy smoke haze over the city, and people who did have asthma needed to take care," Dr Seward told AFL.com.au.
"The smoke haze has cleared pretty well this morning, it's moderate compared to yesterday [Tuesday].
"Both players and the public, if there is a heavy smoke haze, need to carry their medication with them.
"And if there's a heavy smoke haze players who have asthma would need to ensure they used their preventers in the lead up to the game."
The weather bureau said the smoke haze could linger for a couple of more days.
"From the fires over Gippsland we've had easterly winds blowing a lot of that smoke over southern Victoria," duty forecaster Dean Stewart told AFL.com.au.
"It may not be as thick as it was yesterday morning but there will still be smoke in the down there today."
Thursday and Friday's NAB Challenge games are at Etihad Stadium which will give the AFL the option of closing the roof.
Twitter: @MattThompson
