Mr Zhang Guohui was waiting in line at the Ministry of Manpower (MOM) Services Centre at about 3.30pm on Monday when the loud, shrill alarm went off.
"I was startled and I didn't know what was happening at first," said Mr Zhang, 34, a Chinese national who works as a construction worker here.
Before he knew it, MOM officials decked in bright orange vests acting as fire wardens began directing him and other members of the public out of the building.
"This way please," one fire warden said politely, pointing to the carpark in front of the building. "No need to rush," said another.
Mr Zhang soon found out from them that it was MOM's first fire drill at their new frontline division building at Bendemeer Road, which became fully operational in June this year.
"The fire wardens explained to me what was going on, and they were very patient and calm. No one panicked," said Mr Zhang in Mandarin. "I came down to make some inquiries about my work permit, but I understand this exercise is for everyone's safety."
About 800 people were involved in the drill, which was organised by the National Fire and Civil Emergency Preparedness Council (NFEC).
This is also part of its month-long Mass Fire Evacuation Drill campaign, which 172 premises have signed up for, said the Singapore Civil Defence Force (SCDF).