Emergency Services Minister Mick Gentleman said the trucks spent most of their time on public roads, and retrofitting them with so-called "falling object protection systems" could create hazards for other motorists.

However, he would consider investing in upgrades if advice from the Emergency Services Agency changed.

Volunteer firefighters and the opposition last week raised concerns that ACT Rural Fire Service vehicles were not fitted with special bars and cages to protect crews from falling trees.

The potentially fatal consequences of falling trees in bushfires was put in sharp focus during the nation's horror summer. Two volunteer firefighters were killed in late December after a tree fell on their tanker south-west of Sydney. Another man died after a tree collapsed on him in Omeo, in Victoria's alpine region, in mid-January.

Three firefighters were injured after two trees fell on their truck as they were responding to the Orroral Valley Fire in Namadgi National Park.

The Emergency Services Agency last week acknowledged that its trucks weren't fitted with the protections, but noted the vehicles did have the highest safety rating.

The agency said the topic was of "high importance".

Fronting the media on Tuesday, Mr Gentleman was asked why the vehicles weren't fitted with extra protections.

He said ACT Rural Service chief Joe Murphy had advised him that the fire trucks spent most of their time on public roads, and therefore needed to meet certain Australian design standards.

"There is some opportunity to use fall protection if these particular vehicles are spending most of their time in the bush," he said.

"But most of the time they are travelling on our public roads and we don't want to provide further safety issues for other road users across the ACT."

Mr Gentleman said he would consider upgrades if new advice was put to him.

He was comfortable that firefighters sent to rural locations - such as Namadgi National Park - were provided with appropriate protection.

Firefighters were fitted with personal protective equipment, while the vehicles all met safety standards, he said.

Mr Gentleman also faced questions on Tuesday about the government's failure to meet its hazard reduction targets in the months before the Orroral Valley fire tore through Namadgi National Park.

He confirmed that planned hazard reduction work had to be called off due to the outbreak of the fire.

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He stood by the expert advice which determined if prescribed burns were carried out or not.

"The [ESA] commissioner's view is that we should make sure that our firefighters are safe when taking on these duties," he said. "I will not risk the safety of these firefighters."

Asked if the government needed to revise its hazard reduction targets, he said: "I think we need to look at a lot of things going forward".

Mr Gentleman also repeated that he had been advised that "no amount" of planned burning would have stopped the Orroral Valley fire, which burnt through more than a third of the ACT's land mass after igniting on January 27.

Opposition emergency services spokeswoman Giulia Jones said the government should call on volunteer firefighter brigades to help with hazard reduction work outside of the bushfire season.

"Given that we will supposedly have less days to do this work, the number of people engaged must be bolstered, so that on the good days we can get through much more," Mrs Jones said.