Backburning preparation works to the north of Lowanna, west of Nana Glen and west/north west of Glenreagh are "putting a lot of smoke into the sky", the Mid North Coast RFS team said last night.

"This backburning will continue through into this evening and into tomorrow," they said. "The relatively still conditions mean that the smoke will be slow to move away."

The work is being done to make things as safe as possible before the next hot, dry, windy days.

As temperatures warm up today, a total fire ban has been issued for Far North Coast, North Coast, Greater Hunter, Greater Sydney Region, New England, Illawarra/Shoalhaven, Central Ranges and Northern Slopes.

Preliminary analysis of emergency department data shows that hospitals in the Mid North Coast have had 68 presentations to emergency departments for asthma or breathing problems over the last week, almost double the usual number.

"Smoke from the bushfires that have ravaged so much of NSW has led to a rise in people seeking help at public hospitals," NSW Health Director of Environmental Health Dr Richard Broome said.

"Air quality has been very poor, so this increase isn't unexpected. The good news is while the ED presentations have increased, the number of people requiring admission to hospital has remained about the same.

"The increase in presentations is across all ages and it serves to reinforce the message that people with asthma and other respiratory problems should take care on smoky days. It shows that smoke from active and smoldering fires can have a real impact on people's health.

Dr Broome said the smoke might cause no more than eye or throat irritation for most people, but that those with known respiratory conditions, like asthma, need to be cautious when smoke is about.

"People with breathing conditions should avoid outdoor physical activity when there's smoke around and people with asthma should also follow their Asthma Action Plan and carry their relieving medication with them," he said. "If you're prescribed a preventer puffer, it's really important to be taking it at the moment."

"The best way to reduce exposure to smoke is to stay indoors with the doors and windows shut. Air conditioning can also help to filter particles from indoor air," Dr Broome said.

Dr Broome said despite the increase in ED presentations, NSW hospitals are well prepared to deal with emergency situations such as the bushfires, and there was still a long way to go this summer.

"These bushfires have been devastating, but they will not be the last fires in NSW over the coming months. Staying cautious in smoky conditions will continue to be the best way to stay safe."