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You have many responsibilities when you own or manage a building. From the roof to the basement and everything in between, it's your job to make sure everything is up to code and working properly. But one area you might not know much about is atrium smoke control.
The main objective of atrium smoke control is to limit the spread of smoke and heat through the atrium to maintain a tenable environment and allow safe egress for building occupants.
Atrium smoke control can be challenging because atriums have wide, open spaces. As a result, when there’s a fire on a lower level, the atrium allows for the movement of smoke up to the higher floors, increasing the risk of smoke inhalation in areas remote from the fire origin. This is especially dangerous in older buildings constructed without modern features of smoke control.
The International Building Code (IBC) defines an atrium as “a space enclosing a floor open to the story above.” An atrium is one of a few types of permitted vertical openings in a building. It is important to understand the nuances of your local building and fire codes since not all atriums require a smoke control system. Likewise, some jurisdictions are more restrictive than the IBC. In accordance with the base IBC, only atriums that connect more than two stories (other than Group I-1 and I-2 occupancies) are required to be provided with an atrium smoke control system. When an atrium is required to be provided with a smoke control system, it must be designed and installed in accordance with the IBC Section 909 and NFPA 92.
Atrium smoke control systems are necessary for keeping the building and its occupants safe. But a smoke control system is only as effective as its design, so here’s what you need to keep in mind.
Once you have reviewed the applicable building and fire codes with locally adopted ordinances and amendments and determined that a smoke control system is required for your atrium, the first step in designing an atrium smoke control system is to evaluate the space and consider the feasibility of mechanical (active) vs natural (passive) means of smoke control. Natural ventilation relies on the buoyancy of hot air to create airflow, while mechanical ventilation uses fans to force air movement.
Natural ventilation, or passive smoke control systems, are often considered more resilient since their performance is not dependent on the functionality of any mechanical systems. Another type of smoke control system that could be considered a type of natural would be a smoke-fill approach, in which the volume of the space is used to the advantage of maintaining tenability.
Natural ventilation relies on the buoyancy of hot smoke to drive its movement vertically through the atrium, making this approach most effective for atriums with large upper bowls where smoke can collect and passively fill the volume without impacting occupants or when the building is provided with louvers directly open to the outdoors at the top of the atrium so the hot smoke can rise and escape the building.
However, passive atrium smoke control that is dependent on natural openings to the exterior (for a means of exhaust) is heavily impacted by weather conditions, such as wind and stack effect (summer and winter temperatures), which is why a mechanical smoke control system is provided more often.
Fire modeling can be performed by one of our expert smoke control engineers to determine if some method of natural ventilation and/or passive smoke filling is an option for your atrium.
Mechanical exhaust, or active smoke control systems, use fans to extract smoke from the atrium to the outdoors. This approach is often used in atrium applications where natural ventilation isn’t possible or practical. Exhaust fan sizing and location are dependent on multiple factors that can be evaluated through a fire modeling analysis. It’s also important to keep in mind that mechanical ventilation systems require makeup air into the atrium to operate effectively. Makeup air can be provided through exterior openings such as doors and windows, mechanical methods, or a combination of both. You want to carefully consider certain factors for the makeup air, including velocity, location and aesthetics.
Fire modeling can be performed by one of our licensed fire protection engineers to determine the most efficient mechanical smoke control system for your atrium.
Finally, you'll need to consider controls and sequence of operations, such as method(s) of activation, manual overrides for fire department operations, indications, monitoring, emergency power, the shutdown of other HVAC systems, open and closing of louvers, dampers and makeup air supplies, integration with the fire alarm and sprinkler systems, etc. Many of these requirements are prescribed within Section 909 of the IBC.
Status indicators and manual overrides are provided at the firefighters' smoke control panel (FSCP). System activation is usually by means of smoke detection. There are three main types of smoke detectors: spot, line-of-sight (beam detectors), and air-aspiration. Spot detectors are best suited for small atriums, while line-of-sight or air-aspiration detectors are better for larger atriums and arenas or where a very early warning is needed.
Ensuring both individual component and system functionalities are crucial for the performance of atrium smoke control systems.
Preparation of the Smoke Control Rational Analysis (SCRA) is the most important step in the design of an atrium smoke control system and is required in accordance with Section 909 of the IBC. The SCRA documents all the key performance elements and design approach for the system and should be safeguarded for the life of the building. To understand why this document is so important, check out the six key components of a smoke control rational analysis.
An atrium smoke control system involves many components and integrations, including doors, dampers, fans, and fire alarm devices. These elements work together to keep smoke from spreading through the building in the event of a fire. Annual testing and inspection are required per Section 8.6, Periodic Testing, of NFPA 92, Standard for Smoke Control Systems, and the International Fire Code (IFC) to keep your atrium smoke control system working properly. In addition to regularly inspecting and testing the system’s components, it is important to perform routine maintenance in accordance with each component’s manufacturer recommendations to ensure your system performs its job if a fire starts; these requirements differ for dedicated smoke control systems and non-dedicated systems, so it is important to understand the types of systems in your building.
Performance Based Fire can assist in developing a smoke control testing plan for your new or existing smoke control system. We work with local jurisdictions to ensure compliant testing methodologies and reporting. Get ahead of the failed inspection report and avoid a costly fire watch by properly maintaining your building’s smoke control system.
Atrium smoke control keeps occupants safe in the event of a fire by exhausting smoke and ventilating the space. So, when it comes to designing and maintaining your atrium smoke control system, put your trust in a team of reliable fire protection engineers to ensure successful results.