Why did the Hong Kong high-rise fire spread so fast? Green mesh, styrofoam materials under scrutiny

Key Concepts

• Flammable Materials: Bamboo scaffolding, styrofoam, and green mesh (polymers).
• Ignition Sources: Cigarettes, short circuits, gas pipe bursts, man-made causes.
• Fire Spread Factors: Flammable materials, wind, debris, aging coatings.
• Fire Testing Standards: AS5113 (Australia) for facades up to 10 meters.
• Material Compliance: Styrofoam melting point (180°C), flammability of bamboo.
• Engineering Solutions: Metal scaffolding, prioritizing fire safety in construction.

Analysis of Fire Speed and Spread

The rapid spread of the blaze is attributed to a combination of three highly flammable materials: bamboo scaffolding, styrofoam, and green mesh, all of which are essentially polymers. These materials require minimal ignition to burn vigorously.

Potential Ignition Sources and Contributing Conditions

While residents reported seeing workers smoking on-site for months, the expert opinion is that a cigarette alone is unlikely to be the sole ignition source for a fire of this magnitude. Other potential ignition sources include:

• Electrical faults: Short circuits in electrical boards.
• Gas leaks: Bursts in gas pipes.
• Man-made causes: Accidental ignition by workers.

These ignition sources would need to occur under specific "extra conditions" to trigger such a large-scale blaze.

Fire Testing of Construction Materials

The effectiveness of current fire tests for scaffolding and netting in replicating real-life conditions, which include wind, debris, and aging coatings, is questioned.

• Australian Standard (AS5113): This standard involves testing facades up to 10 meters tall by applying a fire at the bottom. The expert is unsure if similar rigorous standards are applied in Hong Kong or other jurisdictions.
• International Standards: Other international test standards exist and should be considered by Hong Kong.

Investigation and Material Performance

Investigators will examine debris to determine if materials performed as specified. Key areas of focus include:

• Styrofoam: Non-compliant styrofoam is expected to burn, as it melts at approximately 180°C and drips, contributing fuel to the fire.
• Green Netting: This material, typically made of polymers, needs investigation to confirm its compliance with shielding requirements.
• Bamboo Scaffolding: Given its long-standing use in Hong Kong, the flammability of bamboo itself should be tested. If found to be highly flammable, its use in future constructions should be reconsidered and potentially phased out.

Recommendations for Future Prevention

To prevent similar tragedies, the following engineering changes and practices are recommended:

1. External Structures: Replace bamboo scaffolding with metal scaffolding, as seen in Australia, to immediately eliminate fire risk.
2. Construction Industry Practices:
   • Building developers and construction stakeholders must prioritize fire safety in all operations.
   • Avoid cutting corners and instead enforce strict regulations to ensure resident safety.

Conclusion

The rapid spread of the fire was a consequence of highly flammable polymeric materials used in construction. While multiple ignition sources are possible, the investigation should focus on material compliance and the effectiveness of existing fire safety testing standards. Future prevention hinges on adopting safer materials like metal scaffolding and instilling a paramount focus on fire safety within the construction industry.