An aerial view of a controlled burn in the Namadgi National Park.

An aerial view of a controlled burn in the Namadgi National Park. Photo: Katherine Griffiths

Environmental authorities are preparing to conduct Canberra's largest fuel reduction burn in more than three decades, as conditions improve after the summer heat.

On Monday ACT Parks and Conservation crews began an expected three-day, 264-hectare controlled burn in the Namadgi National Park using aerial and ground crews in difficult terrain.

Fire services manager Neil Cooper said crews would work around the clock to complete the burn between Bendora Road and Pipeline Road near the Bendora Dam.

A controlled burn was conducted between Bendora Road and Pipeline Road in the Bendora Dam area of Namadgi National Park, the burn is approximately 264 hectares in size.

A controlled burn was conducted between Bendora Road and Pipeline Road in the Bendora Dam area of Namadgi National Park, the burn is approximately 264 hectares in size. Photo: Katherine Griffiths

More than 35 people are involved in the operation, which is causing smoke to be visible about 15 kilometres from Canberra. Minimal smoke impact is expected for the city.

''This year we have about 1200 hectares we are burning across something like 42 separate planned burns,'' Mr Cooper said.

''Part of the extensive training we give our guys is to take things slowly as needed and to not try and rush things. We are totally at the whims of the weather.'' He said the burn had begun in ''perfect conditions''.

A controlled burn was conducted between Bendora Road and Pipeline Road in the Bendora Dam area of Namadgi National Park. Click for more photos

Controlled burn at Namadgi National Park

A controlled burn was conducted between Bendora Road and Pipeline Road in the Bendora Dam area of Namadgi National Park. Photo: Katherine Griffiths

As well, a larger 6000-hectare burn in the Namadgi National Park will occur in coming weeks, with a control team using 10-day weather forecasts, detailed maps and fire plans to determine when conditions will be suitable.

Mr Cooper said fuel reduction management was of critical importance to public safety and environmental protection in the ACT, regularly affected by bushfires.

Areas not burned in the current fuel reduction effort would help form part of a ''natural landscape mosaic'' and could be burned in future operations.

Mr Cooper said the larger burn would begin after sufficient rain eased dry conditions and difficult ecological conditions could be managed effectively.

ACT Parks and recreation crews are involved in efforts with interstate and international teams, refining the science of fuel reduction.

''We had 27 guys go to Victoria for the fires there and people go between places like America and Canada to gain better skills and knowledge from their teams,'' he said.

The ACT Health Directorate advised people with asthma, other chronic respiratory and cardiac diseases to avoid vigorous exercise and to stay indoors if affected by smoke.

Mr Cooper said crews would monitor the fire areas after burns.