The testimony was delivered on the second day of the fifth round of evidentiary hearings before the independent committee investigating the deadly Tai Po fire.
Richard Yuen, chair professor of architectural engineering at City University of Hong Kong, told the committee that his team conducted full-scale fire tests at Sichuan University of Science and Engineering to determine whether scaffolding materials contributed to a secondary ignition effect.
The team constructed a three-storey mock-up of Wang Cheong House – the building where the fire originated – including the walls and windows of adjacent units, as well as combustible items that would normally be found in the units.
During the tests, the researchers compared four different types of scaffolding mesh: uncertified mesh, fire-retardant mesh, non-fire retardant mesh and samples taken from Wang Chi House, the only building not damaged by the fire.
Yuen highlighted one test in particular: when combining safety nets collected from Wang Chi House with non-fire retardant canvas, the result was a complete and total spread of fire across the entire scaffolding system.
He added that fire-retardant materials significantly reduced the severity and spread of fire.
In his written report, Yuen identified two key factors behind the blaze’s escalation: “the accumulation of combustible materials and the presence of suspected non-fire retardant materials in the re-entrant space”.
He added that the build-up of combustibles provided the fuel, while non-fire retardant materials facilitated growth, ultimately allowing the fire to develop into a full-fledged and fast-moving inferno.
The academic also noted that weather conditions on the day played a role.
Dry air had reduced the moisture content in the scaffolding, making it more susceptible to ignition, and strong winds supplied additional oxygen and carried burning embers, further accelerating the fire’s spread, he said.
