The objective of a smoke control system is to maintain a tenable environment for building occupants and allow sufficient time for safe egress, as well as to minimize property damage and business interruption.
During conceptual building design, balancing form with function may be challenging while striving for prescriptive compliance. Many variables, from walls and openings, to areas and volumes of rooms, to ventilation, climate, and building contents, all contribute to the ability of a building to provide the Required Safe Egress Time (RSET). Focusing on the impact of these variables through a performance-based design process often allows for architectural feature flexibility helping to achieve an ideal design vision.
Smoke Control Management: A Crucial Part of a Fire Protection System
For many, hearing the term “fire protection” stirs thoughts of fire alarms and sprinkler systems. However, fire protection is a symphony of systems designed to work in harmony to protect occupants during a fire emergency. Most people understand that a sprinkler system is intended to control fire through wetting and that a fire alarm is intended to alert occupants to the danger of a fire. Many fail to realize that fire protection in the built environment encompasses far more than the protective devices you see. These protective measures can include, but may be not limited to, suppression, detection, notification, egress considerations, interior finish, horizontal and vertical fire barriers, venting and smoke control.
A smoke control system is utilized to control smoke movement and keep exits tenable during a fire. It is a vital part of the system of systems that work together with active and passive components to protect occupants. Smoke control/management or SCM aids in fire protection, which is one aspect of the fire protection puzzle that is often misunderstood.
Smoke Control/Management is defined as an engineered system with the intent to control smoke movement. Smoke control/management (SCM) systems are comprised of multiple components that work in tandem to provide a tenable environment for the evacuation or relocation of occupants during a fire event.
Modern Building Codes, Standards and Technical References provide direction and guidance when a SCM system is required, and what measures are needed for compliance of a properly functioning system. Each jurisdiction may have their own criteria to follow as well, but at a minimum the following Codes, Standards and Technical References should be incorporated:
- International Building Code
- International Fire Code
- NFPA 92, Standard for Smoke Control Systems
- Society of Fire Protection Engineering (SFPE) Handbook
- Handbook of Smoke Control Engineering
- ASHRAE Guideline 1.5
It is important to note that each jurisdiction may impose all the previously mentioned codes, standards and references along with specified amendments/bulletins. The SCM designer must consider all applicable codes, standards, references, amendments/bulletins and editions relevant to the project.
The adopted Building Code dictates when a SCM system is required. Note, this criterion is specific to certain applications and does not consider performance-based options for alternate means and methods. The following is a generalized list of design features that require SCM systems from the 2018 Edition of the IBC:
- High-Rise Buildings (IBC, Section 403)
- Atriums (IBC, Section 404)
- Underground Buildings (IBC, Section 405)
- Group I-3 Buildings (IBC, Section 408.9)
- Stages Larger, Platforms and Technical Production Areas (IBC, Section 410.2.7.2)
- Special Amusement Buildings with an Occupant Load of 50 or More (IBC, Section 411.1)
Approaches to Smoke Control Management
The SCM designer has a variety of approaches to incorporate as the basis of their design. The following methods are commonly utilized to design a SCM system, Passive, Pressurization, Airflow, Exhaust, and Natural Ventilation.
Passive SCM systems prevent smoke and fire from migrating across a physical barrier/smoke zone though a listed construction assembly. Commonly, these assemblies are referred to as rated fire/smoke barriers (e.g. listed walls and floors). It is common to have openings within the barriers (e.g. doors/windows/shutters) which would also carry their own approval listing.
Pressurization SCM systems consider a pressure difference across a barrier/smoke zone so that during a fire event, smoke on a low-pressure zone does not migrate towards the high-pressure zone. For example, one may consider a smokeproof enclosure (e.g. stair pressurization).
Airflow SCM systems utilize airflow to avoid smoke migration beyond the fire zone specific to building elements that contain fixed openings. The airflow is specified with a velocity that correlates to a design fire and associated smoke temperatures in mind. Additionally, these parameters are generated based on the geometry of the opening in question. Airflow SCM systems are for smaller openings such as a pass-through window.
Exhaust SCM systems utilize mechanical means to draw smoke out of large enclosed spaces in order to maintain tenability. These systems are widely used and typically protect large volume spaces (e.g. atriums, arenas).
Natural Ventilation SCM systems utilize the buoyancy effects of smoke and openings (mechanical or manual) to allow for smoke migration to draw up and out of a space through an opening to the exterior of the building. These systems are normally not utilized in climates that have inconsistent weather, as varying temperatures and sporadic wind speeds can have negative outcomes. These systems can be found in smokeproof enclosures more often than they are for atriums. Overall, these systems are the most challenging to design for proper compliance with environmental variables.
Considering the various methodologies for smoke control management, each system can be designed utilizing one or a combination of the available approaches. When a SCM system utilizes other building components/systems that are employed for normal building operation (e.g. HVAC) it is referred to as a Non-Dedicated system. A SCM system having its own standalone equipment/purpose is referred to as a Dedicated system. Either option selected will have to factor in variables that are presented in the project/site location.
Once a project requires a SCM system, it is generally considered best practice that the proposed approach and supporting documentation are agreed upon with the owner, design team and AHJ prior to the system being developed further. This agreement is based around a Design Brief that conceptualizes the SCM system and preliminary design parameters that come in play with the project. A Design Brief maintains accountability of all parties responsible for the intent of the system as it develops. This effort is typically captured during the Schematic or Design Development phase.
As the SCM design progresses, a report documenting intent, assumptions, sequencing, methods of operation, and environmental variables will be compiled in a Rational Analysis. All SCM systems are modeled by empirical hand calculations or computational fluid dynamics (CFD) programs. These models are essentially cookbooks that demonstrate compliance when, at a minimum, the following project/site specific variables are incorporated into the model.
- Stack Effect
- Temperature Effect of Fire
- Wind Effect
- HVAC Systems
- Duration of Operation
- Smoke Control System Interaction
Once the Rational Analysis is complete, it is required to be submitted during the Construction Documents phase and accepted by the AHJ before the system is constructed and commissioned.
Smoke Control System Inspections
Prior to the completion of the installation of the SCM system, the design team is required to retain a design professional that can carry out the Special Inspection (SI) of the system. The SI professional is required to have extensive background in fire protection engineering, mechanical engineering and certification as air balancers. Once a SI professional has been engaged by the design team, they will develop a Special Inspection and Testing Report that will again be submitted and agreed upon with the AHJ. This report outlines the test procedures that will be influenced on the SCM system. The goal of the SI report is to exercise the SCM system to ensure proper compliance as designed/approved in Rational Analysis and associated design documents. It is important that the SCM system is pretested ahead of the SI and the design team coordinates roles, responsibilities and efforts accordingly/effectively. Upon completion of the SI, a final report outlining the associated testing, and field measurements (e.g. airflows/pressure differentials, amperage/voltage, etc.) is documented and submitted to the AHJ for record, along with a report left in the Fire Command Center and one with the Owner.
On-going testing and inspections are required for SCM systems to ensure proper modulation, sequencing, and functionality of the system in respect to the original Rational Analysis and design documents. Modern systems have been equipped with automatic diagnostic testing programming (e.g. UUKL) that communicate to various data point within the SCM system. In the event a portion of the system malfunctions, a notification would be sent to the Firefighter’s Smoke Control Panel that would allow facility personnel or service technicians to self-report. Additionally, there are guidelines as to when a SCM system is required to be inspected for compliance. Periodic testing is required for Dedicated systems at least semiannually with Non-Dedicated systems to occur at least annually. Although an existing system may appear to be in working order, it is paramount that the system is routinely inspected.
In the event any portion of the system is modified or changed, it is best practice to ensure that the original design intent is maintained. In the event it is not, a redesign of the system and update to the original Rational Analysis is required. This update would require the approval of the AHJ.
Fire protection comes in many forms, from standalone systems to a network of integrated systems programmed with logic. Smoke Control/Management blends the principles of standalone and a network of intelligent systems into a dedicated and non-dedicated system. The methodology behind either system is backed by engineering principals and empirical research specific to each project and location. The framework for each system considers environmental impacts, building geometries, fuel loads, and documents any assumptions and agreed upon considerations, which can be found in the Rational Analysis. Quality assurance guidelines are outlined for commissioning and ongoing inspections, tests, and maintenance for each of these systems. Although Smoke Control/Management systems vary, the underlying goal is to promote a tenable environment for evacuation during a fire event.
Smoke Control Management Systems: Expert Fire Protection Consulting
Telgian Engineering & Consulting, LLC (TEC) offers engineering and design services for smoke control systems including passive smoke compartmentation, shaft/zone pressurization, atrium/floor smoke exhaust, and post-fire smoke purge. TEC has extensive experience in specifying smoke control systems for complex building environments with an in-depth understanding of the underlying fire science and human behavior. TEC utilizes state-of-the-art modeling tools to simulate smoke development and human evacuation while working closely with clients to develop cost-effective smoke control solutions that enable a higher level of architectural design freedom.
Leading the industry since 1985, TEC is a full-service global engineering and risk mitigation consulting firm specializing in complex, multi-discipline public and private sector projects. TEC provides professional services related to the protection of people, property, information, and organizational mission against preventable losses. Solutions include strategic/enterprise risk management, fire protection engineering, industrial security, environmental health and safety, emergency management, operations continuity consulting, and construction administration services. TEC professionals are dedicated to delivering value through effective protection solutions that meet today’s unique risk challenges. Contact us for immediate support at 1.302.300.1400 or firstname.lastname@example.org.