Singapore's Formula One race remains on track for the weekend despite the haze, with organisers offering disposable face masks to patrons.
Masks that cover the nose and mouth can be purchased at merchandise booths, organisers said, adding that they would be keeping tabs on haze readings while the sporting event kicks off on Friday.
"The haze situation is highly changeable not only from day to day, but from hour to hour," a spokeswoman for Singapore Grand Prix said.
The latest air pollution readings and health advisory will be available on the official website and mobile app, and also broadcast on screens and radio during the event.
Singapore and large parts of Malaysia have been blanketed in ash and smoke emanating from illegal burning to clear land for plantations in neighbouring Indonesia.
Atalanta progressed to the Europa League semi-finals despite losing 1-0 to Liverpool on Thursday as they triumphed 3-1 on aggregate to move one step closer to a first ever European final for the Serie A side.
Antonio Ruediger scored the decisive penalty as Real Madrid beat holders Manchester City in an edge-of-your-seat 4-3 shootout victory to reach the semi-finals of the Champions League after the teams were locked at 4-4 on aggregate following extra time on Wednesday.
Bayern Munich's Joshua Kimmich powered in a 63rd-minute header to give them a 1-0 victory over a toothless Arsenal on Wednesday and send them through to the Champions League semi-finals for the first time in four years with a 3-2 aggregate win.
Rafael Nadal said it was a challenge to hold himself back on his return to the ATP Tour after three months on the sidelines but the fiercely-competitive Spaniard expects to continue with the controlled approach in Barcelona.