Considerations to be Addressed Before Reopening a Building with a Smoke Control System
A common topic throughout the country lately has been the reopening of buildings that have been left unoccupied during the Covid-19 pandemic. One of the most important things to do it to make sure that all of the fire protection and life safety systems have been properly inspected, tested, and maintained before reintroducing occupants. In order to assist with that we have created a checklist for the most common systems (https://www.nfpa.org/-/media/Files/Coronavirus/CoronavirusReopeningBuildingsChecklist.ashx). Now that we have covered the most common, we need to start looking into some more important systems that may not be in every building. An example of one of these other systems that needs to be addressed before reopening a building is a smoke control system.
Smoke Control Systems
Smoke control systems are commonly found in high rise building stairwells and elevators, detention and correctional occupancies, large assembly seating areas, and atriums (https://community.nfpa.org/community/nfpa-today/blog/2018/01/03/101wednesdays-soaring-to-new-heights-atriums-and-the-life-safety-code). These systems are engineered to protect the occupants in the building as they evacuate, contain the fire in one location, and to aid the first responders as they try to find the fire and extinguish it by:
- containing the smoke and products of combustion in one location in the building
- keeping the smoke and products of combustion out of a given space
- or removing the smoke and products of combustion out of a given space in order
When thinking of smoke control systems, you can think of them in two categories, smoke containment systems, and smoke management systems. Smoke containment systems include stairwell pressurization, zoned smoke control, elevator pressurization, vestibule pressurization, and smoke refuge area pressurization. Smoke management systems are typically found in large volume spaces such as large assembly seating areas and atriums, these types of smoke systems include natural smoke filling, mechanical smoke exhaust, gravity smoke venting, and opposed air flow.
System Design and Testing
When these systems are designed, an engineering analysis is performed per NFPA 92, Standard for Smoke Control Systems to ensure that specific design criteria are met. For example, if the system is being designed to keep the space tenable for occupants to evacuate, then some of the design criteria will include maximum temperature and minimum visibility in the spaces occupied during building evacuation, typically this is the space from floor level to a height of at least 6 feet (1830 mm). The design of these systems includes calculations and computer models that are run based on how the space will be used, because of this, it is the building owner's responsibility to limit the use of the space, so it is consistent with the limitations provided in the operations and maintenance manual. Such limitations include but are not limited to maximum fuel size and minimum distance between fuels. Additionally, the building owner is responsible for all system testing per NFPA 92 and must maintain records of all periodic testing and maintenance in accordance with the operations and maintenance manual that was provided with the system upon acceptance testing.
Testing for dedicated smoke control systems needs to be performed semi-annually and non-dedicated systems (I.e. those that utilize a buildings HVAC system) need to be tested annually. The system must be tested by persons who are thoroughly knowledgeable with the operation, testing, and maintenance of the system. When testing, each system needs to be tested against the specific design criteria that it was designed to under both normal power and standby power, all of the pass/ fail criteria should be provided in the design documents. The system needs to be operated for each of the sequences in the design criteria, this could include testing different smoke zones and testing different initiating devices such as smoke detectors, waterflow switches, and pull stations (if provided). For each of the inputs, all of the correct outputs (such as dampers opening/closing, doors opening/closing, and fans turning on/off) needs to be confirmed that they are operating per the system design.
The periodic testing needs to confirm that the pressure differences across smoke barriers, at air makeup supplies, and at smoke exhaust equipment coincide with the data points taken during initial acceptance testing. When testing is performed on these systems it is possible that a significant amount of outside air will be introduced into the building, as such, special arrangements need to be made to protect sensitive equipment or building contents from a change in temperature and/or humidity.
As you can see, there is a significant number of things that needs to be tested on a smoke control system, and it is all system specific. If your building contains a smoke control system, or you think it may contain a smoke control system, you should contact a qualified person prior to reopening to ensure that all of the proper inspection testing and maintenance has been completed to ensure the safety of all of the occupants within your building.
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