Education Minister Verity Firth recently announced a list of the first 101 schools to have their 2738 unflued gas heaters removed before next winter.

There are 51,000 unflued gas heaters being used in schools around the state.

A government-commissioned independent report by the Woolcock Institute of Medical Research said the unflued gas heaters "increased respiratory symptoms" but there was no "measurable adverse changes in lung function".

The report found the increased risk of cough and wheeze was "greater in atopic [allergic] subjects, who represent over half the population".

It recommended the use of another source of heating because of the adverse effect on asthma sufferers which is best avoided.

A spokesman for Ms Firth said the report recommended a sensible and measured approach to removing the heaters but there was no undue cause for alarm.

"There is a 5 per cent increased risk of coughing and wheezing in students so we will be removing the heaters," he said.

Sonia Gale's six-year-old daughter Emma, who has asthma, attends Leppington Public School, where the unflued heaters are either not used or only operated with proper ventilation such as classroom doors or windows left open.

"She has asthma and she's always coughing and getting chest infections," Ms Gale said.

"The K/1 room has airconditioning but they should still get the heaters out of there."

Asthma Foundation NSW chief executive Michele Goldman said: "While the government tried to downplay the statistics and the risk these heaters pose to health, the study's author has said that the statistics are 'significant' and in a health context that means these heaters must be removed."

Ms Firth's spokesman said the department used Australian Bureau of Meteorology statistics to find the coldest schools in the state which would have their heaters removed first.

He said it was agreed by all stakeholder groups that the schools in the coldest areas would have priority.

When asked if having an unflued gas heater in every classroom could have also been a factor in the priority, the spokesman said that data from the bureau was the fairest way for them to proceed.

He said that there will be a further announcement soon on when the heaters will be removed from schools that were not on the list.

Camden MP Geoff Corrigan did not wish to comment.