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High CO2 levels on Sydney trains: report

Passengers on Sydney Trains are breathing in more than double the normal levels of carbon dioxide found indoors, a report from an environmental monitoring group has found.

The testing, undertaken by environmental monitoring devices company OnSolution on the morning of February 6, found carbon dioxide levels in carriages reached above 2000 parts-per-million (ppm) on some peak hour train services in the city circle.

The normal limit of carbon dioxide in a building is 1000ppm with University of Sydney's indoor environmental quality lab director Richard de Dear saying overcrowding leads to higher carbon dioxide levels.