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Edge of the Slab Fire Protection (Curtain Wall Joint)

Posted by Vipul Chouhanover 5 years ago

Understand how fire and smoke can travel through curtain wall joint and why is it necessary to seal this gap.

Curtain Wall,Passive Firestop,Edge of the Slab

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Current Scenario:

In the past couple of decades, India has seen a revolution in the construction sector like no other country. The ever-increasing demand for new offices and commercial spaces coupled with lack of land has given birth to an era of high rise structures with innovative and unique façade systems. There are several parameters that are considered for design of these structures and fire safety is one of the critical ones. Though we have made significant progress in all aspects of fire design in the past decade, fire safety of facade installation is one such area where still a lot of pondering needs to be done. There have been several accidents in the recent past due to poor fire protection of facade which serves as wake-up call and motivates us to find solutions.


Am I safe if the fire is not ongoing or has not originated from my floor ?
In 1988, First Interstate Bank building in Los Angeles caught fire on the 12th floor extending to the 16th floor in a 62-storey building. It was identified as per the investigation that the fire was originated on the 12th floor and spread to upper floors via lift shaft and the unprotected openings at the edge of the floor slab and the façade system.
In 2012, Four floors of the 57 years old Heritage building, Mantralaya situated in Mumbai were gutted due to short circuit in the IT department located on the 4th floor of the 7 storied building.

In both these cases, fire and smoke freely travelled throughout the building and subsequently damaged areas located far from the origin of the fire. 


Can fire and smoke propagate through unprotected gaps ?

In certain types of façade systems, we encounter a perimeter void typically of the range from two to eight inches between each floor slab and the exterior curtain wall. Perimeter voids are generally hidden from view after construction. Once installed, due to their location, such gaps are never inspected or re-evaluated unless some major retrofitting work is taken up. When such openings are left unprotected, they provide the perfect space for the fire and smoke to spread upwards. It is very important to seal these gaps to prevent the spread of flames, smoke and toxic gases in case of a fire breakout.


In what ways can fire spread in a curtain wall system?
Fire can spread in a curtain wall through chimney effect, leapfrog effect and/or poke through effect.
1)     Chimney effect:
Chimney effect is attributed to the spread of fire upward through the available openings between the floor slab edge and the curtain wall.
2)     Leapfrog effect:
Leapfrog effect is seen in mid to high rise building fires where flames blasting out through perimeter windows leaps through the windows above and continue to spread vertically in a similar pattern on every floor
3)     Poke through effect:

Poke through effect is where flame and hot gasses penetrate through openings in fire rated walls and floor/ceilings ignite combustibles on the other side.


Summary

There are different ways in which fire and smoke can travel from one floor to another. It becomes inevitable and absolutely necessary to seal these gaps in curtain wall systems with a system of fire rating equal to the floor’s fire-resistance rating. This in turn will ensure that sufficient time is available to evacuate people and damage is limited by restricting the movement of fire and smoke till the fire tender arrives.





3 comments on this article
Posted by ASIF AKBARIabout 5 years ago
How can we design the curtain wall section. If I want to start with, how should I initiate?

Posted by Vibhavari vermaover 5 years ago
very good content

Posted by Dhrmeshover 5 years ago
Rich content with detailed explanation. Very useful article..