ACT chief health officer Kerryn Coleman has granted an exemption for the Brumbies and Canberra Raiders to play in front of up to 6000 people at Canberra Stadium.

It means the Brumbies are set to host their biggest crowd of the revamped Super Rugby campaign in the decider at Canberra Stadium on September 19.

ACT Chief Minister Andrew Barr has lauded the decision with club officials anticipating the remaining tickets on offer will be snapped up in the coming days.

"In ordinary terms if you said you're going to get 6000 for a grand final you'd be very disappointed but in the context of this year, the Brumbies will be pleased and it will mean more members and fans can get to the game," Barr said.

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"The measures and protections that have been put in place for the players and to keep spectators one and a half metres apart have worked well in the rounds leading into the finals.

"Given the capacity of the venue, you can have 6000 physically distant who can enjoy the game. It'll give greater atmosphere to the venue, not quite the same as Canberra Stadium full, but must better than playing in front of hundreds or no crowd at all."

Government officials concede events in large venues carry an increased risk of COVID-19 transmission, but moving to a 25 per cent stadium capacity was endorsed by the Australian Health Protection Principal Committee in June. The ACT has not recorded a new COVID-19 case in more than eight weeks.

About 5000 of the Brumbies' season ticket holders have been gifted access to free tickets to the decider as a "thank you" for sticking by the club during a tumultuous campaign marred by the coronavirus pandemic.

"It's super exciting, I'm super excited for our fans. They've come out and braved the cold all year, and they're super passionate about the team," Brumbies star Scott Sio said.

"For the inaugural year of Super Rugby AU, for us to host a grand final is pretty special. It's something we're definitely looking forward to. We need to make sure we do the right things this week to set us up for it."

Tickets will be released in stages so officials can scale the attendance back if restrictions tighten. The first allocation of 1500 was snapped up within minutes on Wednesday.

The second round of member ticketing became available on Thursday. Non-season ticketed members and registered community players can purchase tickets from Friday morning.

Those who have signed up to the ticketing waitlist will be able to access seating from Monday should any remain. The remainder will go on sale to the general public from Tuesday morning.