Integration: HVAC fans and smoke control
Fire, life safety, and HVAC systems must be integrated by the engineer to achieve reliability in smoke control systems. This includes mechanical equipment, physical barriers, or a combination of both.
- Explain the basics of a smoke control system.
- Assess the codes and standards that must be applied when designing a smoke control system.
- Identify the ways to test and document the successful design of the system.
The 2015 edition of NFPA 92: Standard for Smoke Control Systems, defines dedicated smoke control systems and nondedicated smoke control systems as:
- Dedicated smoke control system: Smoke control systems and components that are installed for the sole purpose of providing smoke control and that upon activation of the systems operate specifically to perform the smoke-control function.
- Nondedicated smoke control system: A smoke control system that shares components with some other system(s), such as the building HVAC system, which changes its modes of operation to achieve the smoke control objective.
The most recent edition of the International Building Code (IBC) requires the implementation of smoke control systems in a limited number of building scenarios. Atriums connecting more than two stories, underground buildings with occupied levels more than 30 ft below the finished floor of the lowest level of exit discharge, windowless detention or correctional facilities, stage ventilation, and/or assembly spaces using smoke-protected seating are required to be provided with a smoke control system. Although high-rise structures only require smoke-removal systems for post-salvage operations, implementation of smoke control systems in high-rise towers is a common occurrence. Additional requirements based on local jurisdictions, corporate-brand requirements, or as a result of possible alternate means and methods may also require the smoke control system.
The most common building component in which truly dedicated smoke control systems are used is a pressurized exit or smoke-proof enclosure, such as a high-rise pressurized stairway. This is due to strict requirements imposed by codes and standards, which regulate how these building components are to be serviced and subsequently allowed openings within dedicated exit enclosures. Other building components where dedicated smoke control systems will predominantly be used are pressurized elevator hoistway systems or atriums.
Outside of these buildings components, smoke control systems most likely to be encountered are typically nondedicated smoke control systems, or hybrid systems, which combine the use of dedicated and nondedicated equipment. For example, multi-use buildings (i.e., hotel resorts and casinos) with podium-level smoke control systems where high ceilings are furnished will typically be designed to the air-change or exhaust method. With activation of the associated smoke zone, it is common for mechanical makeup air to be provided by building normal-use air-handling fans. Smoke exhaust will be provided by either dedicated smoke-exhaust fans for hybrid systems, or at times by the return side of air-handling units or general-exhaust fans that double as smoke-exhaust fans, for true nondedicated systems.
Typical smoke control systems provided in high-rise towers will be classified as hybrid systems and will customarily be designed to use either the pressurization method or air-change method of smoke control. Within these vertical structures, common vertical shafts can serve to transfer conditioned air to each level during normal use. During a fire scenario, these same vertical shafts will provide exhaust or supply air, as needed, when the system is configured for smoke control. Supply air for the air-change method of smoke control oftentimes will be furnished by a nondedicated rooftop air conditioning unit and exhaust provided by a dedicated smoke-exhaust fan for both pressurization and air-change methods.
Advantages, disadvantages of systems
The above nondedicated and hybrid system examples integrate equipment used on a day-to-day basis for normal building conditioning and ventilation requirements in addition to serving life safety functions. A considerable benefit of incorporating this methodology of design is that system impairments are more likely to be identified and addressed promptly. Dedicated smoke control system impairments have the potential of not being recognized as readily, which can negatively impact the effectiveness or impair the system during a life safety scenario. Other benefits to employing nondedicated system designs is the consolidation of equipment functionality, which results in less building area being tied to the housing and placement of equipment.
These systems also can reduce control-system components. A reduction in the overall number of fans and air-distribution duct systems can be accomplished when integrated (nondedicated) systems are applied. Furthermore, in most cases there will be a reduction in the costs related to equipment acquisition and maintenance.
Once operational, for many properties, ongoing tenant improvements and renovations are a common occurrence. Caution needs to be taken when this occurs, especially when nondedicated systems are involved. These types of activities have the potential to negatively impact smoke control systems, particularly integrated systems, unless a complete understanding of the intended design and functionality of impacted equipment and systems is recognized at the onset of the project by the responsible design professional. Unintentional impairment to smoke control systems can occur due to smoke-zone boundary reconfigurations, equipment modifications, equipment replacements, equipment additions, or alterations to system programming, among numerous other possible scenarios.
With the implementation, construction, and installation of smoke control systems, certification or commissioning of these systems by a qualified special inspection agency is required by many of the governing codes. Section 1705.18 of the 2015 edition of IBC states, “Smoke control systems shall be tested by a special inspector.” Subsequent subsections provide the general scope of testing requirements and required qualifications the inspector shall meet.
Section 11.8.1 of the 2015 edition of NFPA 1: Fire Code requires newly installed smoke control systems be inspected by the authority having jurisdiction (AHJ) in accordance with NFPA 92. Furthermore, section 9.3.1 of the 2015 edition of NFPA 101: Life Safety Code indicates smoke control systems will be inspected and tested in accordance with NFPA 92. Section 9.3.3 of NFPA 101 states, “Acceptance testing shall be performed by a special inspector … ” The 2015 edition of NFPA 4: Standard for Integrated Fire Protection and Life Safety System Testing provides standardized testing protocols for integrated life safety systems, which may be applied to the commissioning of smoke control systems.
Commissioning of smoke control systems will be in accordance with the approved design documentation, applicable building code, and AHJ requirements. System commissioning by a special inspection agency requires confirmation of each smoke control system in its entirety, including installation and the ability to achieve intended design criteria. The commissioning process for smoke control systems by the special inspection agency is ideally executed in a consistent, specific progression of activities as follows; test plan preparation, field/equipment inspections and testing, system sequence testing, performance testing, and secondary power confirmation. With the phasing of construction being common practice, the following progression of commissioning activities will be applied to each individual smoke-control zone to the greatest extent possible.
Qualified contractors will complete equipment installation, programming, sequence pretesting, system air balancing, and confirmation of proper performance of all smoke control systems and associated components. Coordination and oversight of this effort are to be provided by the general contractor for the project. The responsibility or role of the special inspection agency is only to inspect and witness testing of complete and functional systems. Otherwise, there may be conflict-of-interest issues if their level of involvement is beyond the previously stated scope of services.
Benefits of a test plan
During the initial stages of the commissioning process, review and acceptance by the AHJ of the proposed means and methods to be employed by the special inspection agency is common practice in many jurisdictions. Customarily, documentation of the proposed scope and method of inspection and testing is achieved through the preparation of a test plan. A test plan serves multiple purposes; it conveys the approach and sequence of inspection and testing activities for each component and associated smoke control system. It provides a means to document the organization of commissioning activities and estimated time frames. It outlines each trade’s responsibilities and interactions. Smoke control system performance criteria will be established, and equipment and system outputs to be measured and recorded will be established, for the purpose of determining effectiveness and functionality of each zone.
As negotiations and special conditions are common, the test plan can corroborate agreements or accepted deviations from standard procedures reached with the AHJ. The general contractor can reference the test plan to schedule and coordinate construction activities in addition to identifying impacts on day-to-day operational activities throughout the construction process. Furthermore, the test plan can minimize miscommunications and misunderstandings that may occur during the commissioning process and, with any luck, reduce any surprises to all parties involved.
Included within the test plan will be test scenarios, prepared by the special inspection agency, which are reflective of the engineered system’s functional matrix prepared by the engineer of record. Test scenarios are integral to the process of sequence testing of the smoke control systems as they provide necessary equipment configurations and pass/fail criteria for each zone in a condensed, convenient format.
Preparation of a test plan will occur once all pertinent information related to the subject smoke control system is attained and reviewed by the special inspection agency. This allows the responsible party to become familiar with the subject smoke control system design, the system locations, layout and zoning, the system’s intended functionality, performance requirements, and required pass/fail criteria. Design documentation required for the purpose of preparing the test plan and test scenarios include the smoke control system rational analysis and/or fire protection report, including amendments, smoke control diagrams, HVAC system plans, fire protection and fire alarm system plans, master egress plans, and equipment data sheets for all devices and apparatus associated with the smoke control systems.
Once the test plan has been prepared, allowing all interested parties the opportunity to review and comment on the test plan and scenarios prior to submittal to the AHJ is recommended. This helps to confirm that the special inspection agency’s expectations are reasonable and attainable before providing the AHJ a plan that is not viable. Following this review and comment phase, the test plan can be finalized and submitted for review and acceptance by the jurisdiction.
While the test plan is similar between dedicated and nondedicated systems, there are certain things that need to be considered for each. For example, nondedicated systems may use control equipment or variable frequency drives (VFDs) for comfort control that are suitable for smoke control systems. For dedicated systems, in cases where the management of the smoke control system is shared between the building management system and fire alarm system, controls for dedicated equipment can be overlooked in the installation and construction process; therefore, their operation needs to be carefully reviewed and tested.
Field/equipment inspections and testing
The initial process of performing special inspections of any smoke control system consists of first breaking down a system into its individual components. With this process, each piece of equipment and component of a smoke control system will be individually inspected and tested to confirm installation, functionality, and control. This process is to include the review of smoke-zone boundary construction and configuration, and automatic sprinkler system zoning. Equipment inspections are intended to confirm the specified manufacturer and model is installed, installation is per the manufacturer’s requirements, and the installation complies with the approved design documentation. This includes the associated air-distribution system ducts, automated dampers (i.e., control dampers, fire/smoke dampers, and smoke dampers), fire doors, and affiliated fans. At this stage of testing, power to equipment and basic functionality will be confirmed (i.e., automated dampers and doors fully open and close) and failure positions will be witnessed, as applicable.
Duct inspections will affirm proper configuration, inlet and outlet locations, and compliant support and bracing. Duct supports will be verified to consist of adequate noncombustible stable supports directly anchored to fire-resistance-rated building structural components. Duct inlets and outlets are to be located per the associated design documentation. Locations of smoke-exhaust-fan discharge points are to be inspected, as they relate to supply points of fans or other points of entry to the building. This is intended to confirm discharged smoke will not be reintroduced into the building, thereby potentially endangering occupants remote from the fire incident.
Inspection of system ducts is best performed before installation of ceilings has occurred to allow an unobstructed view of these components. Early in the commissioning process, witnessing of duct leakage is to be fulfilled for ducts, as required by the approved design documentation, prior to enclosure within shafts. Leakage testing of ducts will be witnessed by a certified air-balance agency hired as a subconsultant to the special inspection agency, or by an individual with the appropriate certifications hired directly by the agency.
Inspection and testing of smoke-zone boundaries will be initiated early in the project and continue until the conclusion of the commissioning process. Multiple visits may be required, to complete all necessary visual inspections of the barriers. Field inspections will confirm that smoke-zone boundary configurations match design documentation and the visual continuity of the barriers. Inspection of the top-of-wall portion of the barriers is best completed before ceilings are installed. Throughout the construction process, new openings and penetrations within smoke-zone boundaries are a common occurrence and should be monitored by the special inspection agency to ensure wall continuity is maintained.
The primary purpose of these inspections is to confirm sealing of penetrations within the smoke-zone barrier for the purpose of maintaining necessary construction tightness. Verification that penetrations are compliant with the associated listed systems is not within the scope of the smoke control system special inspection agency. During performance verification of a smoke control system, final confirmation of the smoke-zone barrier continuity is ascertained based upon the associated system achieving the necessary performance objective.
As with ducts, inspection of sprinkler system zoning is ideally completed prior to the installation of ceilings. This will allow unobstructed views of piping configurations to accurately determine proper installation within the boundaries of the associated smoke control system. Sprinkler riser assembly locations are to be confirmed to match locations indicated in the approved smoke control diagrams.
Damper inspections will confirm that the device location, proper access, installation, fire protection rating, leakage rating, operating temperature, and listings are in compliance with the system design requirements. Each damper is to be cycled fully opened and closed and the associated detector initiated to confirm automatic control. Power supply to each fire/smoke and smoke damper is to be removed to verify appropriate fail-safe positioning.
Similar to dampers, doors in smoke-zone boundaries are to be inspected to confirm proper location, installation, fire protection rating, and listings in accordance with approved design and applicable building codes. Confirming proper closure and latching while the associated smoke control systems are inactive will determine the functionality of doors under normal conditions. Functionality of the doors with the associated systems active will be completed during the performance testing process. Control of roll-down doors, drop-down doors, accordion-style doors, and doors provided with hold-open devices will be verified through initiation of local detection devices and other required control sequences.
All fans included in the sequence of operation of smoke control systems are to be field-verified for location and installation in accordance with approved design documentation. Units required to energize with activation of a smoke control system are to be inspected to verify a minimum service factor of 1.15 and 1.5 times the number of belts required for design duty are installed for belt-driven fans, with a minimum of two belts provided. Fans intended to exhaust smoke are to be suited for probable temperatures resulting from a fire scenario. Units complying with recognized listing agency specifications are routinely installed. Where units are not available that comply with this requirement, as is the case with air handlers, it is admissible for manufacturers to assemble fans using components suitable for operation at elevated temperatures. An accompanying engineering judgment prepared by the fan manufacturer is necessary to justify the unit’s suitability for operation at the predetermined elevated temperatures. For fans provided with a VFD, an appropriately listed drive is to be employed.
While testing of dedicated and nondedicated systems is similar, there are certain aspects of each that need to be verified. For example, nondedicated systems may have portions of the system that extend beyond zone boundaries, or control equipment that needs to be overridden during an alarm condition. Dedicated systems will need to be reviewed carefully to ensure other building components, not related with life safety systems, do not interfere with the functionality or code compliance of the system.
System sequence testing
Once each component of a smoke control system has been inspected and tested as an independent apparatus, each system will be confirmed to activate and operate in accordance with the approved functional matrix. Proper system configuration, control, and monitoring will be verified under automatic and manual activation at the firefighter’s smoke control panel for all smoke control systems. With activation of each system, the special inspection agency will confirm the system response time is in compliance with the system design as well as referenced standard prescriptive requirements.
Control and monitoring of nondedicated smoke control systems tend to be more complicated, when compared to dedicated systems, due to the necessity of maintaining normal functionality balanced with life safety responsibilities. This factor can impose a certain amount of difficulty during the commissioning of the related smoke control system. The main concern will be to ensure that the building management system’s programming and functionality is in place, including air balancing, prior to the onset of inspection and testing of the associated smoke control system. This will allow the special inspection agency to confirm that life safety system functions of the integrated system will override the building management system’s normal functions in a smoke-control scenario.
Sequence testing requires all initiating devices associated with each smoke control system be activated to confirm proper system response and configuration, per the approved system functional matrix. Through this process, control and programming of devices and systems are verified. Prior to activation of each smoke control system, associated equipment is to be field-inspected in its normal condition. Nondedicated fans and dampers are to be operational and under control of the building management system preceding these efforts. Following initiation of a properly zoned fire alarm device, each piece of equipment is to be field-inspected for proper alarm status per the system design. Once configured for smoke control, equipment status monitoring will be confirmed.
Proper monitoring of equipment operational status, upon configuration for smoke control, can be confirmed through force-fault testing. Force-fault testing is accomplished through altering the required operational status of monitored equipment opposite of its intended condition. Therefore, dampers or power-operated doors that are commanded to close with smoke-control activation will be forced open; energized fans will be de-energized. This confirms proper fault conditions are identified and properly displayed by the system. Final verification of the proper monitoring of fans will be completed following the conclusion of performance testing of an associated smoke control system. The special inspection agency is to rely on the responsible contractors to determine the appropriate manner in which to manipulate the equipment to accomplish the desired faulty outcome. Caution should always be observed throughout this process, so as not to damage any of the associated systems and/or equipment as a result of force-fault testing activities.
During the sequence testing process, smoke control system response to subsequent alarms is to be verified to be in accordance with the approved design documentation. This requires automatic activation of each smoke control system, and, once properly configured, additional alarms will be initiated to confirm the appropriate system response occurs. It is common for the first alarm sequence to be maintained, but, as stated above, this is not always the case. The special inspection agency is required to confirm appropriate outputs per applicable design documentation.
When using air conditioning units as part of a nondedicated system during the inspections and testing of the associated smoke control system, attention is to be paid to the potential of the units’ integral static pressure limit switch de-energizing the unit when configured for smoke-management functions. Upon configuration of a smoke control system, the air-distribution network of a system many times will be altered through opening and closing of automated dampers, to direct supply air to or mechanically exhaust specific areas of a building. With alterations of the distribution system, substantial changes in the static pressure within the system can occur, resulting in the unit’s safety feature shutting down the fan. This causes a failure that will have a major impact on the effectiveness of the smoke control system. Although uncommon, prudent practice is to ensure the limits of the static pressure sensors are sufficiently adjusted to account for system variations, which will occur under normal and smoke-control conditions.
In conjunction with testing the automatic activation and control of each smoke control system, manual override capabilities of the firefighter’s smoke control panel are to be verified. With no alarm active, the priority of the firefighter’s smoke control panel will be verified through manual activation of each smoke control system, confirming override capability of normal functions of the building management system. Additionally, confirming manual override capabilities of automatic alarm sequences is necessary.
To perform this, automatic activation of a smoke control system is required. Once the activated system is properly configured, a second smoke control system is manually activated at the firefighter’s smoke control panel. Proper system response should reflect the manually activated smoke control system configuring per the functional matrix, overriding the automatically activated smoke control system. This testing sequence is to be reversed by manually activating a smoke control system, followed by initiating an alarm for a different smoke zone. Proper system response should reflect the manually activated smoke control system maintaining proper configuration. Further testing includes following the automatic activation of smoke control systems, which employ supply fans; each supply fan should be confirmed to de-energize with initiation of the associated duct detection device. With the unit de-energized and the smoke control system still active, the associated system is to be manually activated via the firefighter’s smoke control panel to confirm the affected unit re-energizes.
Sequence testing of the smoke control system must be completed before performance testing begins.
Construction of the building envelope and smoke-zone barriers for each system must be completed before performance testing can proceed. Furthermore, air balancing of each smoke control system, including the normal functions for nondedicated systems, is to be conducted and completed by the responsible contractor prior to the onset of performance testing by the special inspection agency. This ensures the performance of the system is operational in both modes and is not impeded or affected by balancing for comfort control.
Required performance criteria and system characteristics to be confirmed when verifying system compliance are based upon the method of smoke control employed. These benchmarks will be ascertained from the approved design documents and applicable codes and referenced standards. Methods of smoke control that will be encountered include pressurization method, exhaust method, airflow method, air-change method, and positive pressurization method used in smokeproof and exit enclosures. System measurements are to be witnessed by a certified air-balance agency hired as a subconsultant to the special inspection agency, or by an individual with the appropriate certifications hired directly by the agency.
Along with the measurement of airflow characteristics of each smoke control system, side-hinge doors at smoke barriers will be verified to properly open with door-opening forces at or less than 30 lbs, while maintaining the capability to properly close and latch with the system active. Following verification of the performance functionality of each system, operational parameters of active fans serving each system will be measured to ensure stable performance, per the manufacturer’s data. Parameters to be measured and recorded include operating amperes, voltage, static pressure, revolutions per minute, volumetric flow rate, horsepower, proper rotation, belt tension, and VFD settings if applicable.
Final verification of proper monitoring of smoke control system fans can be completed at this time. The performance of a “belt on/off” test for belt-driven fans confirms a fault will be provided to the system upon the loss of drive belts. With this test, the smoke control systems are activated by automatic or manual initiation, per the discretion of the special inspection agency. Once proper system status is provided at the firefighter’s smoke control panel, the belts of a fan are removed and the fan is energized to confirm a trouble status is provided at the control panel. Fan belts are then reinstalled and the fan energized to confirm proper run status is restored at the firefighter’s smoke control panel. This test will be conducted for all fans energized and monitored with activation of a smoke control system. Belt on/off testing is essential for dedicated systems, since these units only operate under smoke-control configuration.
Secondary power confirmation
Confirmation of the secondary power source for smoke control systems is performed through the transfer from the primary to the standby power source. Typically, this will occur after all other inspection and testing activities by the special inspection agency have been satisfactorily completed and the firefighter’s smoke control panel has been proven to accurately reflect the status of each system.
Prior to the transferring of power sources, the most demanding smoke control system is to be activated with proper system configuration verified at the smoke control panel. Once configured, transfer of the power will be performed. During this process, the special inspection agency will confirm the transfer to full standby power occurs within 60 sec, or by the time frame indicated in the approved design documentation. With the property powered by the secondary power source, each associated smoke control system will then be activated and verified to properly configure and maintain operation under standby power.
Further equipment field inspections should be performed to verify proper rotation of smoke control fans is maintained under standby power. As part of these efforts, the secondary power source will be confirmed to maintain operation of the smoke control systems for a time equal to, or greater than, the required duration of operation as indicated in the approved design documentation.
Special inspections documentation
Throughout the commissioning process, the special inspection agency is required to maintain documentation on all necessary and relevant inspection and testing activities. Documentation is required to be thorough and precise. This includes daily activity reports, deficiency notifications, equipment and device documentation, and measured performance data relative to each smoke control system and associated equipment. At the completion of the commissioning process, a final report will be prepared by the special inspection agency, outlining the scope of efforts and results of the inspection and testing activities with all pertinent special inspection documentation provided within this report. The final report will be reviewed, signed, and sealed by the engineer of record for the associated smoke control systems, prior to submittal to the AHJ for review and acceptance. The commissioning process should be the same for both dedicated and nondedicated systems.
Commissioning of smoke control systems is a necessary, detailed, and lengthy procedure that needs to be accounted for at the onset of each project to minimize the impacts the process will have on construction deadlines. Proper planning and coordination of the design and construction process will be required from all interested parties to ensure a successful commissioning process. This begins with the system designers providing a compliant, detailed, and complete system design suitable for the intended building/space to be protected; it extends through the entire design, construction, and commissioning process. At the completion of the process, through comprehensive and detailed inspections and testing by a qualified special inspection agency, the commissioning process will result in proven and compliant smoke control systems when turned over to the owner.
Key components in both dedicated and nondedicated systems need to be considered to properly test and commission these systems. While nondedicated systems can save overall building costs, their dual use can include additional equipment that may impact life safety functions. For dedicated systems, testing needs to confirm that they will operate when needed since they are not used on a regular basis.
Mark Mecham is a senior fire protection engineer at JBA Consulting Engineers. Mecham has nearly 15 yr of experience in fire protection and life safety. He is experienced in witnessing the verification of smoke control and fire alarm systems, production of smoke control diagrams, and preparation of life safety reports.