Any air-quality reading over 200 is hazardous according to the NSW Office of Environment and Heritage (OEH), which monitors a range of pollutants including air particles, visibility and carbon monoxide.

Between 4am and 5am in Kembla Grange on Monday, the air quality index revealed visibility reached 1398; before dropping to 810 by 6am. It remained in the 'poor' (100 to 149) to 'very poor'(150 to 199) range throughout Monday.

Poor to very poor particle levels were also recorded in Kembla Grange on Monday (remaining at 153 at 3pm), related to a hazard reduction burn at Avon Dam across the weekend.

Weather conditions have meant the smoke drifted east and settled around Dapto, Horsley and surrounding areas with a thick haze and smell of smoke visible for much of Monday.

NSW Ambulance Inspector Norm Rees said the smoky conditions had led to a rise in Triple 0 calls for people with respiratory issues across the region.

"We're experiencing locally an increase in patients with breathing difficulties being assessed by our crews and assisted with medication," he said.

"Those with underlying respiratory conditions tend to have their symptoms aggravated by smoke, so we'd urge people to stay indoors as much as possible when there's a lot of smoke around.

"If they are concerned they should call for an ambulance."

Dr Graham Hart, Illawarra Shoalhaven Local Health District Director of Respiratory Medicine, said local emergency departments were often inundated after a lot of smoke due to bushfires or backburns.

"We often see a spike in ED presentations around the time of increased smoke and for a few days afterwards, as symptoms worsen," he said.

"Those usually worst affected are those with chronic lung disease, including obstructive pulmonary disease (COPD) and emphysema, as well as asthma."

Dr Hart advised those at risk to stay indoors as much as possible, avoid strenuous exercise and use their reliever medicine. Those with asthma should stick to their Asthma Action Plan.

An OEH spokeswoman said the particle levels at Kembla Grange would remain high until Tuesday afternoon.

"There may be some additional (reduced) smoke impact in the Illawarra on Monday evening before the southerly change hits early on Tuesday morning," she said.

"Hazard reduction burns cause smoke, which increases (particle) pollution and reduce visibility.

"The hazard reduction burns are critical in fuel management to mitigate the impacts of bushfires, and are conducted with input from meteorologists.

"However, the low-wind conditions that are most conducive to safe prescribed burns mean that particles take longer to clear."