People with asthma are being urged to take care as sudden rises in temperature and smoke from bushfires could worsen symptoms and trigger a dangerous attack.
Smoke from bushfires contains tiny particles that go deep into the lungs and irritate the airways, says Asthma Foundation NSW CEO Michele Goldman, who is worried about a heatwave in the state.
"We should be mindful that asthma claims the lives of over 400 Australians each year."
People undertaking a strenuous activity, such as bushwalking, should do it when there is a low risk of bushfire and the pollution index is medium to low, she says.
"It is vital that all asthmatics continue to take their preventer medication and carry their reliever medication with them at all times.
"Everyone with asthma should have a written action plan so they know how to respond if their asthma becomes worse."
Unless they are ordered to evacuate, people with asthma should stay indoors if there is wood smoke in their area.
Windows should be closed and air conditioners should be set to recirculate.
Ordinary face and dust masks and handkerchiefs do not filter the fine particles from bushfire smoke, Ms Goldman says.
Special P1 and P2 masks are effective, but they make it harder to breathe and are hot and uncomfortable.