Firefighters were called to the Macquarie Street premises just before 10am Sunday when a fire alarm sounded.

A loud siren and repeated pre-recorded warnings of "Emergency, evacuation now!" could be heard from streets away.

When it appeared there was no immediate danger, Nationals Dubbo campaign manager Peter Bartley said he phoned the security company, the property's managing agent then NSW Fire and Rescue in order to put a stop to the noise.

"One of our smoke detectors went off - I don't know what caused it," he said.

"Possibly dust got into it."

Firefighters inspected and declared the site safe a short time later.

Mr Bartley said he was particularly glad the fire alarm had not gone off and prompted an evacuation the night before, when party faithful had gathered to see the NSW election results unfold.

"Actually, we may not have heard it above the jubilation," he said.

"No doubt our party would have spilled out onto the street.

"But yes, very glad it wasn't a real fire".