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Under Pressure: Fire Curtains and Zone Pressurisation

Posted April 27, 2018

As the popularity of fire curtains as a passive fire protection method grows, the increasing number of fire curtain products on the market is a source of confusion for many. Often, the effectiveness of fire curtains is undermined by the inappropriate design of building services and incorrect specification of the curtains themselves. There is particular confusion surrounding the relationship between fire curtains and zone pressurisation, with designers frequently – and incorrectly – assuming that fire curtains will perform the same as the wall it is replacing. In reality, many fire curtains perform poorly in response to pressure differentials, resulting in the lifting of the bottom bar, damage to the fire curtain, and billowing of the fabric, all of which pose a significant risk to egress paths near the curtains.

What is zone pressurisation?

In a fire event, smoke can only flow from a high-pressure space into one with a lower pressure. As such, zone pressurisation systems maintain positive pressure in egress paths by using mechanical fans to inject air into the stairwell or corridor. While this keeps egress paths free of smoke, it also results in a pressure differential that may cause the curtain to billow and – in extreme cases – the fabric edges to blow out, rupturing the barrier between the fire and safe spaces.

In Australia there is a requirement for this pressure differential to be a minimum of 20Pa and a maximum of 100Pa. For fire curtain systems to work properly, the pressure differential should be minimised as much as possible.

How can the effects of pressurisation on fire curtains be minimised?

To combat the risk of failure to the building design, the pressurisation system needs to be design such that the pressure differential across the fire curtain can be adjusted during commissioning. It is imperative that the start up to the pressuriasation system is delayed until the fire curtain is fully deployed to ensure that the fire compartment is created first.

To prevent fabric billowing or edges blowing out, fire curtain systems typically incorporate posts at corners or regular intervals along the curtain’s length. These posts provide extra support for the curtains and hold them taut and in place as flames and radiant heat cause pressure to change around them.

Other options include a retention system featuring steel side guides that prevent the fabric from blowing open, the use of offset rollers and curtain overlaps, and increasing the rigidity of the fire curtain textile.

FireMaster Concertina

Providing up to 4 hours of integrity during a fire event without corner posts and is resistant to billowing and blowing out, Greene Fire’s FireMaster Concertina is the lead solution for protecting voids and intertenancy stairs that also incorporate zone pressurisation.

Featuring a unique, pleated design, Concertina™ is engineered and proven to perform in high-pressure environments. Strips of heavy-duty inflammable textile are stitched together horizontally, forming a pleated design that unfolds to a sturdy barrier during a fire event. When retracted, the pleats neatly refold to their stored position and are concealed within the bottom tray, which provides complete access into the headbox when deployed.

Concertina’s pleated surface structure is self-supporting, allowing it to provide outstanding protection from smoke, heat, and superheated gases without corner posts. Architects and designers are given unmatched freedom in fire protection specification, with Concertina capable of installation in polygons, right angles, irregular shapes, and even complete circles up to 6m in height. Concertina™ has been assessed to AS 1530.7 – Methods for fire testing on building materials, components and structures – Smoke control assemblies and has a demonstrated FRL of – / 240 / – and leakage rate of 3.1m3/m2/hour.

When tested in accordance with AS 1668.1 – The use of ventilation and air conditioning in buildings, the FireMaster Concertina demonstrated performance as part of a smoke pressurisation system at over 60Pa. The fire curtain was shown to achieve a 20Pa pressure differential on all floors – the minimum required by AS1668.1 – and to work at pressures as high as 60Pa across its surface, a figure three times as high as when tested for fire resistance.

In addition to specifying the FireMaster Concertina, designers should engage a team of mechanical engineers and fire engineers to model leakage throughout building systems and collaborate on designing a complete fire protection system that ensures maximum safety. Learn more about the FireMaster Concertina and Greene Fire’s extensive range of fire and smoke protection systems at products page.

Case stude on fire curtains in zone pressurisation can be downloaded at

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