Fair Work commissioner Nicholas Wilson ordered the vote to take place within 20 working days on Monday, after the United Firefighters Union's ACT branch applied for a protected action ballot order last week.

The Australian Electoral Commission will conduct the ballot, which will ask the union's more than 330 ACT members whether they support taking industrial action in support of reaching an enterprise agreement with ACT Fire and Rescue.

For industrial action to be authorised, at least half the eligible members would need to participate in the ballot, and at least half of those taking part would need to vote in favour of the measure.

There are 21 proposed methods of industrial action, but the union's ACT branch secretary Greg McConville has said none will affect public safety because firefighters will still respond to incidents.

Emergency Services Agency commissioner Dominic Lane has said the agency will continue to work with the union and that it will comply with any Fair Work Commission orders.

The dispute between the union and the agency comes after 26 meetings since April 2017 failed to yield a new enterprise agreement for the ACT's urban firefighters.

Mr McConville told The Canberra Times last week union members "almost unanimously" rejected an offer in December that included a 10 per cent pay rise because they wanted that money invested in the fire service instead.

He said the pay rise would have been in exchange for the loss of some key employment conditions for firefighters, including that the union must agree with the agency on a number of standards around fire stations, equipment, recruitment and training.

The union believes ACT Fire and Rescue needs an extra 204 firefighters in the next four years to cope with increasing demand, staff new and upgraded fire stations, and improve firefighter training.