Fire in Helsinki apartment block spread rapidly through ventilation gaps, expert says

A fire that broke out in a Helsinki apartment building on Saturday spread unusually fast from a fourth-floor balcony to the roof of the eight-storey structure, according to an insurance specialist analyzing the incident.

Antti Määttänen, claims director at insurance company Lähi-Tapiola, told Yle that the rapid spread—reaching the top floors within minutes—was likely facilitated by the building’s ventilation gaps acting like chimneys. In confined spaces, he explained, flames can accelerate upward at exceptional speed.

“Ten minutes is enough for fire to travel upward through such a channel,” Määttänen said, though he noted that combustible material within the gap likely fueled the spread. While ventilation gaps are mandatory to prevent moisture damage, he suggested this case may expose a regulatory blind spot: “It’s possible this was a code-compliant solution, yet still led to rapid fire progression.”

The blaze, which began during balcony grilling, prompted the evacuation of the top two floors. No injuries were reported. Määttänen emphasized that exterior fires in apartment blocks are rare, as building codes prioritize internal fire containment. He also warned that grease fires from unclean grills are notoriously difficult to extinguish with standard methods like fire blankets, recommending powder extinguishers instead.

Authorities will investigate whether construction errors or material choices contributed to the fire’s spread, with potential revisions to building regulations if the design is found compliant yet unsafe.