Passive Fire : The Second Side of Fire Life Safety

Mr. Tariq Kachwala (Director) FG Glass

What are the key features of fire-rated smoke screens that make them important in buildings, and how do they help prevent the spread of fire and smoke?

Fire-rated smoke screens are a crucial architectural element in several constructions today. These screens are installed in areas where smoke reservoirs need to be created in case of fire, such as escalator shafts, to prevent smoke from spreading from lower to higher levels, or between the same floor horizontally. Smoke screens are also installed in atriums to prevent smoke from individual levels from entering the atrium and into other floors.

Smoke screens offer significant benefits by limiting the spread of smoke which aids people’s rescue and fire suppression operations. During rescue operations, smoke screens also help keep people safe from smoke inhalation when they move from lower to higher floors, reducing the risk of death due to suffocation.

How can architects and building owners ensure that fire-rated smoke screens are installed correctly and meet the necessary safety standards, and what are the consequences of failing to do so?

The National Building Code of India has mandated the use of smoke screens in escalator shaft applications in its new chapter on fire and safety. However, architects and building owners should also consider using smoke screens in other applications to ensure comprehensive passive fire protection and facilitate rescue operations.

One common mistake in architectural design is the use of regular laminated glass for smokescreen overhangs instead of fire-rated glass. In India, where a minimum of two hours of passive fire protection is required, the temperature of smoke can exceed 250 degrees Celsius, which soda-lime toughened glass cannot withstand.

Toughened soda-lime glass has a thermal shock capability of only 120 to 150 degrees Celsius, which means it can crumble and disintegrate easily in the event of a fire and high smoke temperature. Laminated glass also poses a risk of falling as a hot glass lump and injuring or killing people below it. In contrast, fire-rated glasses such as those with a borosilicate composition can withstand smoke more than 300 degrees Celsius and surface temperatures over 1000 degrees Celsius for over two hours.

Architects must also ensure that smoke reservoirs are constructed comprehensively from the core RCC ceiling level down to where the glass overhang ends. A common mistake is not ensuring that the supporting structure has certified plaster modes of minimum 24 mm thickness on either side of a GI framework. This should be installed to provide comprehensive smoke reservoir protection from the ceiling to the glass overhang. If not executed properly, smoke can pass through weak elements of the construction, defeating the purpose of the installation. Architects and consultants should carefully review the test evidence and ensure that construction details and all components installed match exactly with those tested, with no compromise on cost.

What are some of the most innovative and effective fire-rated smoke screen technologies currently available, and how are they changing the way we think about building safety and fire prevention?

As mentioned above, fire-rated smoke screens have several important applications. The most significant of these are in escalator shafts and as overhangs in atriums. Depending on the building application, partitions may even be created on either side of the escalator shaft so that smoke on one side of the floor does not transfer to the other at the same level. In addition to stopping the spread of smoke to the upper level, it is essential to ensure that all components used in the construction are exactly the same as the test evidence.

At a minimum a glass of 6 mm thickness should be used in fully toughened form, which ensures safety breakage characteristics. Smoke screens can be constructed in various formats, and for very obvious reasons glass is the most popular choice for the visible portion of these smoke screens due to their transparency and ability to withstand very high temperatures. SCHOTT has its time-tested and ubiquitous Pyran® S borosilicate glass composition that serves as the ideal material for such screens that not only withstands smoke propagation but also looks aesthetically stunning.

If architecturally required, there is also an option to screen print or digitally print these glazed smoke screens to suit the building aesthetics without any compromise in the performance. Moreover, our advanced processing can also create these smoke screens in curved formats, which could be a great benefit for applications where the atriums are in curved form or the opening about the escalator shaft needs to be curved. Finally, these smoke screens can be installed on their GI framework either with exposed bolts or with concealed fittings, and this is a pure architectural choice.