A Zumba class in Devonport last night took a slightly dramatic turn, following an instructor's decision to introduce a smoke machine to the session.

The smoke billowing from the machine set off the smoke alarm, sending the dancers out and the local fire service in to the JustWorkout gym in the North Shore suburb.

An attendee at the 6.45pm class, who agreed to speak to the Herald under the condition of anonymity, said the instructor was trying to create "vibe" for the class.

"It set off the alarm, two fire trucks arrived and everyone was evacuated," said the avid Zumba-goer.

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JustWorkout director John Webster said the instructor did not mean any harm in bringing the smoke machine to the class.

"She is the most bubbly instructor you could imagine, " Webster said.

"All I can say is that this wasn't intended at all."

A spokesperson from the Devonport Fire Station told the Herald: "It was all over pretty quickly," noting units arrived at 7.24pm and were on to another job a few minutes later.

The Zumba class attendee said dancers were able to re-enter the gym and finish off their session.

While you might think call outs to fire alarms set off by smoke machines would be few and far between, the fire station spokesperson said they are surprisingly common: "Particularly at school discos and performances, people don't really think about it when they're organising."

Earlier this year, the NZ Fire Service released data showing that a third of all callouts were false alarms, most often caused unintentionally.

Details released to the Herald under the Official Information Act showed fire crews attended 77,463 jobs between July 2016 and June 2017, 26,336 of which were unnecessary callouts, and included incidents such as alarms set off by a child and burnt toast.

At the time of the release of the documents, Fire and Emergency New Zealand's national adviser of fire risk management, Peter Gallagher, said false alarms were "frustrating" for fire crews.

"These are events that we want to reduce because of the cost to businesses and the cost to our business of responding, and also the added risk it poses to members of the public who won't acknowledge a real fire alarm when one occurs."

Previously, Fire and Emergency NZ businesses that had more than three false alarm callouts in 12 months were fined $1000, but this rule has since changed with the cost now funded by the fire service.

- This story has been updated after initial publication to include commentary from JustWorkout.