Why can tall buildings constructed with reinforced concrete catch fire? Is it because they contain a material that must be used?

Wood is flammable, but concrete is difficult to burn. This difference confuses people: why do fires occur in tall buildings, and why do they often spread rapidly, engulfing the entire structure?

This phenomenon is closely related to the building materials and internal structure of tall buildings, with the major issue lying in a type of insulation material. This material has caused numerous fires, yet it continues to be used, leaving people puzzled as to why it hasn't been banned.

To understand why this material is still in use, we need to consider its usage.

Fire, for humans, brings both the joy of cooking food and the light in darkness, hence the deep-rooted reverence for it since ancient times.

However, the relationship between humans and fire isn't always harmonious; many disasters are caused by fire.

These fires don't occur in rural, wooden structures but rather in tall buildings constructed with reinforced concrete.

For a fire to occur, three elements are needed: fuel, oxygen, and a source of ignition. While concrete is difficult to burn, the waterproofing layer, insulation layer on the exterior of the building, as well as the furniture and appliances inside, provide the fuel.

Furthermore, fires require sufficient oxygen to burn, and urban skyscrapers are more likely to have an abundant oxygen supply.

During the construction of tall buildings, ventilation is a primary concern, hence the inclusion of ventilation ducts and elevator shafts upon completion.

These ducts easily create a chimney effect within narrow spaces, accelerating airflow and fueling the fire.

When the fire reaches a certain intensity, hot air rises, creating thermal convection, further fueling the flames.

In such scenarios, fires not only threaten the occupants of the building but also attract onlookers below and brave firefighters, making the fire more conspicuous.

However, the intensity of the fire does not correspond to the speed of its extinguishment.

Apart from those directly affected by the fire, others tend to forget after a while, providing opportunities for the recurrence of fires.

All these fires are related to a type of insulation material called extruded polystyrene board.

Made from polystyrene, though moisture-resistant and corrosion-resistant, extruded polystyrene is flammable due to its carbon-hydrogen elements.

Once ignited, flames spread rapidly, vertically upward, engulfing the entire building.

When extruded polystyrene boards burn, they release a large amount of smoke, which not only harms human health but also pollutes the atmosphere, posing significant risks.

Although flame retardancy is considered when using extruded polystyrene, once ignited, it's challenging to control the fire.

However, the problem doesn't solely lie in the material itself but also in how it's used.

Extruded polystyrene isn't the only insulation material available; there are safer alternatives.

Yet, due to the lesser insulation properties of other materials compared to extruded polystyrene, people still opt for the latter.

While construction site management in Europe is stringent when using extruded polystyrene, in other countries, some construction sites neglect safety issues, leaving insulation boards exposed and combustible materials with gaps, increasing the risk of fires.

Therefore, addressing fire issues isn't just about banning hazardous materials; it's also about improving construction site management, selecting safe building materials, and strictly adhering to regulations, thus genuinely ensuring the safety of buildings and people.