Stairwell Pressurisation protects life and reduces property loss whilst ensuring a safe means of exit from a burning building.
In the event of a fire within a high-rise, the only means of escape is traditionally via the stairwell.
The taller the building, the longer it takes for occupants to escape, as evacuees must wait for those most at risk to evacuate first. It is therefore essential that these areas be kept free from smoke and heat for an extended period. Firefighters also rely on the protection of these areas to commence firefighting activities, and to escape if required. To prevent smoke from leaking past closed doors and into the stairwell, a pressurisation system/smoke control system is employed; an engineered system that works to modify smoke movement.
This method uses mechanical equipment to produce pressure differences across smoke barriers. One side of the wall is positively pressurised, and the other side is negatively pressurised. This is done with a combination of air injection, pressure relief and air release from the adjoining fire area. The combination of these three elements is essential to the efficacy of the pressurisation system. Air is injected into the stair enclosure so that the pressure in the stairwell is greater than the adjacent fire compartment. By maintaining a positive pressure in the stairwell and lift lobby, smoke is prevented from leaking into these areas.
If the stair door is opened, the system is intended to maintain a flow of air through the open doorway to oppose smoke flow and prevent contamination of the stair enclosure. Pressure relief vents, such as Apreco’s PRV-123 and the newly developed PRV-F2, will prevent overpressure of the system. These single-way pressure relief vents have been specially designed for use with pressurisation systems in stairwell escape routes.
Pressure Relief Vent safety benefits:
- Protects escape routes and common areas from smoke ingress
- Protects the occupiers of the buildings during an evacuation
- Protects entrance for the fire brigade
- Delays development of the fire
- Reduces damage to the building and its contents
Industry standards
Over the past few decades, fire-safety codes have been forced to adapt to ever-changing architectural trends. As the popularity of large open spaces and corridors without vestibules increases, so does the need for new smoke-control installations and an understanding of these complex systems. The pressurisation of stairwells is the primary line of protection for building cores and failure of the system could place occupants and firefighters at serious risk. The industry standard used for the design, installation and testing of smoke-control systems is NFPA 92.
Apreco’s Pressure Relief Vents have been designed in line with NFPA 92 and BS EN 12101-6:2005 standards for use with stairwell pressurisation systems. The European standards, BS EN 12101-6, specify that pressurised fire escapes must be maintained at 50Pa, and limited to a maximum of 60Pa. Apreco’s Pressure Relief Vents undergo specialist balancing at our UK facility to ensure an opening pressure of 50Pa with on-site adjustment available on the PRV-123.
Experts in pressure relief
While the main principles of pressurisation systems are simple, the variables associated with design and operation are many and complex. Unlike other industry standards, NFPA 92 does not provide a prescriptive sequence of events for testing; each smoke-control system has unique parameters. The most notable being the estimation of leakage from stairway doors, gaps in the wall, windows and through wall materials. This problem becomes exaggerated in very tall buildings, as it can be very difficult to balance the different airflow requirements. An over-pressurisation in the stairwell, for example, can prevent an occupant from opening the closed doors. Apreco’s counterweighted pressure relief vents have been engineered to overcome door opening forces and balancing air flows.
Apreco can provide expert advice at the tender stage of your project, which can result in the most cost-effective solution, ensuring all proposals comply with current industry standards and regulatory requirements. Incorporated in 1997 we pride ourselves in providing a product range and service of the highest standard and integrity. Apreco Limited is an established ISO 9001:2015 UKAS registered company, offering a reassuringly stable and dependable service to its customers.
Apreco’s distinguished range of pressure relief vents is characterised by their ease of installation and accuracy. They do not require any external power source as they work on a counterbalanced blade system.
Do counterweighted vents perform better?
We carried out fan testing of our vents and those of others supplying the market. The test results clearly show that not all vents perform equally, and claims made by some suppliers are overstated.
The results conclusively showed that the counterweighted vents perform significantly better than the top-hung gravity vents, which typically provide 25–40% less free vent area than stated in their manufacturers’ literature.
How much impact do accessories have on the pressure-relief vents’ performance?
Basic accessories provide external weather protection or internal screening. Conventionally, internal screening is provided by eggcrate grilles, which have little effect on performance. External weather protection can be provided either by conventional fixed-blade weather louvres or by dynamic weather louvres, which are top-hung flaps. These weather protection products come with varying degrees of resistance and can impact the overall pressure drop of the system, so care should be taken when selections are made.
If you have a question about our products, our team is ready to help.
For more information, go to www.apreco.com
Subscribe to Gulf Fire today for FREE!