Jakarta's toxic skies have been stuck at unhealthy levels for weeks despite drastic efforts to cut down on congestion, including an odd-even licence plate system and the closure of some schools and toll roads.
The city's air-quality index reading hovered around 107 yesterday, posing a danger for people sensitive to air pollution including those with respiratory problems.
But the index has regularly topped 150 this month, which is considered a health threat to the general population. A reading over 300 is seen as hazardous.
About 16,000 athletes and officials from 45 Asian countries - along with hordes of sports-crazy tourists - are flocking to Jakarta and co-host city Palembang for the showpiece event.
Athletes competing indoors will be relatively unaffected, but it's a different story for outside sports like athletics, archery, baseball, softball and rugby, said Budi Haryanto, an air pollution and health expert at the University of Indonesia.
Competing in an environment with dirty air limits athletes' ability to perform at their best, he added, with Jakarta's average 31 degree Celsius temperatures already threatening to leave competitors drenched in sweat.