Atriums are one of the grander features that can be incorporated into a building design. Still, they introduce several design considerations that should be taken into account as a project progresses through design and into construction. This post will present an overview of some of these major considerations.
Sizing and location of the smoke control exhaust and make-up air are paramount
Typically, the exhaust is located at the top of the atrium, and make-up (or supply) air is located toward the bottom of the atrium, such that the airflow path facilitates smoke being efficiently removed from the space. The goal is to clear enough smoke to maintain visibility for exiting occupants at walking surfaces and egress paths. The number and location of exhaust inlets, as well as the location and distribution of supply air, are both critically important to developing a solution suitable for maintaining a tenable environment for those in the atrium. CFD (computational fluid dynamics) computer modeling can often be used to help simulate the various effects of these design factors. CFD model results can also be helpful visual aids when discussing the evaluation with a building or fire official. For more details on makeup-air considerations, please see our prior blog post on the topic found HERE.
What is the atrium boundary and how is it determined?
All spaces within an atrium are required to be separated from any areas not included within the atrium (IBC Section 404.6). This can be accomplished in two prescriptive ways:
- 1-hour fire barrier walls
- Sprinklers on glass achieving an equivalent 1-hour fire resistance rating
Additionally, there may be an option to utilize smoke curtains listed under UL 10D & 1784 (with building official approval). These options can also be mixed and matched for flexibility in the overall design. Also of note, the code allows for atrium separation to not be provided between the atrium and the adjoining spaces of up to three floors, if the spaces or rooms are accounted for in the design of the smoke control system.
Are there any specific sprinkler or fire alarm features required for the atrium?
Atriums are required to be provided with both automatic sprinkler protection and a fire alarm system. Both the sprinkler and fire alarm initiating devices serving the atrium are required to be appropriately zoned in alignment with the atrium boundary. This is done so that a fire event outside the atrium does not activate the smoke control system (exhaust fans, makeup air, sprinklers, etc.) within the atrium and vice versa. Therefore, establishing and clearly documenting the atrium boundary within design documentation is important for the success of the project.
Is the smoke control system able to be controlled via the Building Management System (BMS)?
The smoke control system is permitted to be controlled by either the fire alarm system or the BMS; however, splitting controls between multiple systems should be avoided. In either case, the controlling system is required to be listed in accordance with UL 864 and specifically, subcategory UUKL.
Determining the most cost-effective means to control a smoke control system generally depends upon the complexity of the system, whether the equipment is dedicated to the smoke control system, as well as other design considerations.
What about the smoke control panel?
Every smoke control system requires a firefighter’s smoke control panel, which annunciates equipment status and provides manual control of system components. The smoke control panel for the fire department is required to be in the fire command center if the building requires an FCC. If the building does not have an FCC, the panel is required to be located at a location approved by the AHJ and is often adjacent to the building fire alarm panel. It is always a good idea to consult with the local fire official on the location and design of the smoke control panel before releasing it for production.
What are some other requirements for an atrium outside of the overall design?
Not to be forgotten, a typical requirement for atrium smoke control systems also includes smoke control special inspections through IBC Chapter 17. Special inspections require a comprehensive understanding of system design, performance, and construction schedules to support rather than obstruct the process. Code Red Consultants has experience stemming from dozens of smoke control special inspection projects, should you need such services.
Additionally, depending on local or state requirements, an independent third-party review of the atrium smoke control design may be required. For example, a third-party review of the project’s smoke control rational analysis (which is required to be developed by IBC Section 909) is required in Massachusetts via state code amendments. The third-party review is completed to establish that the design of the atrium smoke control system is consistent with the generally accepted/established principles of engineering and code requirements relevant to the design. The third-party review should be submitted along with the permit application.
In summary, atriums are a desirable but complex part of building design (and construction). We are happy to bring our atrium and smoke control experience to bear to support the design and/or construction side of your next atrium project. Please contact us at firstname.lastname@example.org for more information.