When the Australian team trained for the first time at the Olympic venue on Monday, it was greeted with a cloud of haze, hovering halfway between the pool and roof.

Thompson asked officials for an explanation, but had not received one.

However, when his team had its morning session at the pool yesterday, the air was clearer inside the Cube.

''We asked the question yesterday and we didn't really get an answer to that,'' Thompson said.

''It was gone this morning and it didn't really have any adverse effect yesterday, so as long as it's gone, that's good.''

International Olympic Committee officials said Beijing's pollution haze would have to be at extreme levels before any events were postponed or rescheduled.

Committee medical commission chairman Arne Ljungqvist said the it would assess a range of data, including daily weather reports, predicted weather, pollution indices, humidity and temperature in the early evening in assessing conditions for the next day's competition.

The commission would look ahead as far as 72 hours in assessing possible changes.

''It would have to be extremely bad in a combination of data for instance if the weather was coming in from the south where there is more industry that is worse than from the north,'' Dr Ljungqvist said.

Shooter Russell Mark was one athlete who felt the pollution would work in his favour. Mark said it was much easier for his ageing eyes to spot the orange trap targets on a white background.

''I don't know how I would go running the marathon a week later,'' he said. Only last week at their training camp in Kuala Lumpur, Thompson was asked if he had any concerns about the pollution in Beijing, particularly as about half of the Australian team suffer from respiratory problems, mostly asthma.

''Most of our activities will be carried out indoors, so we'll be probably one of the lucky ones if there is an issue,'' he said at the time, not realising the smog could get indoors as well.