The short-lived two-week mask mandate was lifted last week despite an extended lockdown in Sydney and mask requirements across all NSW.

ACT Health Minister Rachel Stephen-Smith said the rules were removed because the risk Sydney's situation posed to Canberra was low and there was concern compliance could wear away if the rules remained longer than necessary.

"We've got a small number of people travelling between greater Sydney and the ACT region. Those people are required to get exemptions and go into quarantine," she said.

She said there had been high uptake over the two-weeks, proving if the requirements were re-imposed residents would heed the change.

"It's this kind of constant balancing act, but what I think the Chief Health Officer is really cognisant of, is wearing a mask is uncomfortable and people don't really like doing it," Ms Stephen-Smith said.

"People were extremely compliant when it was mandated, but there is a risk that wears off over time.

"It's really about being very clear with the community about the level of risk that we are facing as a community."

At the moment, Ms Stephen-Smith said that risk was "low but not non-existent" as Sydney's surging outbreak lurks across the border, with another 97 cases announced on Wednesday.

There are no known COVID-19 cases in the ACT while 264 people including those from greater Sydney and overseas arrivals such as diplomats, are in quarantine. A further 1400 people are under stay-at-home orders.

Health authorities identified 26 casual contacts of a man who tested positive after working at a Goulburn construction site, who are in isolation and pose a low risk to the community, according to ACT Health.

Professor Peter Collignon from the Australian National University Medical School, agreed masks shouldn't be mandated in indoor settings while Canberra remained free of community transmission.

"I do think people get sick of them and they don't use them properly, so if you're going to mandate masks it's got to be because there's a reasonable risk at the time," he said.

"Usually that means you've got some community transmission or you've got some suspicion there may be.

Professor Collignon said the virus would continue to present a threat for the next three to four months until a higher proportion of the population could get vaccinated and it was likely masks would need to be mandated again, should the risk increase.

"When we need masks, we need people to wear them and wear them properly," he said.

"You're more likely to achieve that if you don't make people wear masks when the risk appears to be low."

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However, University of Sydney epidemiologist Alexandra Martiniuk said compulsory masks indoors would be a "wise approach" in the ACT, as it was across NSW.

While Professor Martiniuk said it was generally easier for people to maintain a behaviour which became routine.

"Keeping a mandate to wear masks indoors will reduce the cognitive load of trying to remember all the other changes to our daily patterns which do need to come and go [such as lockdowns]," she said.

ACT Chief Health Officer Kerryn Coleman told The Canberra Times last week she wouldn't hesitate to reinstate the mandate.

"One of the reasons for being comfortable lifting the [rules] now is the risk of seeding and hence, transmission, has backed right off, because we've had a really good response to our stay-at-home orders," she said.

"We've had very high levels of testing and we're not picking up anything.

"If there is undetected transmission [and] we think the risk of that might be ramping up ... that's when masks can add some value."

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