The Duncan and North Cowichan South End firehalls responded to a call about smoke filling the round building next to the Duncan courthouse at about 3:30 p.m.
Firefighters were investigating the cause of the smoke.
Before long, there were five fire trucks in the area behind the round building and courthouse.
Several firefighters entered the building wearing Scott air packs to be able to check out any possible sources more thoroughly if smoke was thick.
Eventually, two big fans were carried into the building to help clear the smoke.
Duncan Fire Chief Mike McKinlay said the air conditioning unit on the fifth floor failed and oil and other materials went into the building’s air conditioning system and started to smoke.
The next job is to clear the smoke from the building.