Unlike Melbourne where the outbreak is at its worst, mask wearing is not mandatory in Canberra.

However, ACT Chief Minister Andrew Barr has warned that if more cases were found here, then face masks "will feature as part of our response".

Mr Barr on Monday cautioned that masks would be a "meaningless" device in the fight against the virus if people stopped physical distancing, good hand hygiene and staying at home if they felt sick.

The ACT recorded its third straight day without an active case on Monday, and about three weeks have past since a new infection was detected in the capital.

But local authorities remain wary of the steadily rising caseload in NSW, where a further 13 infections were reported on Monday.

ACT chief health officer Kerryn Coleman said there was some uncertainty as to whether NSW authorities were "right on top" of the outbreaks in the state.

NSW Premier Gladys Berejiklian has encouraged mask wearing in places where it was difficult to physically distance.

Dr Coleman said it wasn't necessary for masks to be worn in the ACT at this stage because the territory didn't have any active cases, let alone any cases of community transmission.

But she said the health advice could change if there was either; a rapid spike of cases in the territory or surrounding region, an outbreak or cluster; or the emergence of infections where the source could not be traced.

However, Dr Coleman said Canberrans should remain vigilant, recommending they prepare for potential future outbreaks in the same way they would for a bushfire emergency.

"We know that coronavirus is going to be with us for six, 12, 18 months ... maybe even two years. I think that we should start thinking about in the same way that we plan for a bushfire," Dr Coleman said.

"What do you do in a bushfire? We need our home kits in case you need to evacuate. So what are some of the things that we need to keep ourselves safe if we do start getting coronavirus cases in the ACT?

"One of them might be some form of mask, but we also need to think about soap, hand hygiene measures."

While urging Canberrans to prepare for an increase of cases, Dr Coleman strongly discouraged locals from stockpiling supplies.

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Mr Barr warned masks were not a substitute for the first-order tactics in fighting COVID-19: social distancing, good hand hygiene and staying at home when unwell.

"It doesn't hurt to [wear a mask] ... I don't want to see it elevated for people to think that just because you are wearing a mask you could go to work even if you are sick or that you could ignore the other three things," he said.

"If you don't do the first three then wearing a mask is meaningless. You absolutely have to do the first three and then wearing a mask adds a little bit of extra value. It is not the number one issue, it's a fourth order issue."

While ACT Health hasn't recommended masks, from Monday Woolworths has strongly encouraged staff and shoppers in Canberra to wear one in store.

"We fully support employers in those decisions," Dr Coleman said.

"But I would reiterate that with the level of cases and no evidence of community transmission ... the community does not need to wear masks at the moment."