While we undertook to build a fireproof room with all non-combustible, fire-resistive and limited or slightly combustible materials, we unintentionally created an unprotected opening through the wall of this room; the question here is whether this compartment is still a fireproof room!
This example embodies the situation when we overlook an essential element of a critical system from fire and life safety protection systems, the fire-rated duct of the smoke control and management system, which plays a vital role in life safety from smoke hazards. For a better understanding of these systems and the targeted element, let us define the following:
- The Smoke: Smoke is a significant contributor to the cause of deaths in fire situations. It naturally occurs when there is incomplete combustion (not enough oxygen present to burn the fuel completely). In complete combustion, everything is burned, producing just water and carbon dioxide; however, it can be influenced by the elements of the original material’s chemical composition. When incomplete combustion occurs, only some matter burns and smoke is a collection of these tiny-unburned particles. Each particle is too small to see with our eyes; however, when these group together, we see these particles as smoke.
- The Smoke Control System: This system controls the movement of smoke and air in a building. These systems have multiple components and use several approaches and methods to achieve their design objective. Typically, the main goal is to maintain a tenable environment long enough for all occupants to leave the building and provide safe operations for responding firefighters inside the buildings during the incident.
- The Smoke Control Duct: an essential part of smoke and heat control systems. These ducts can serve a single compartment or across several fire compartments. The duct may be dedicated to smoke control and management systems or possibly a combined environmental ventilation/smoke purpose.
Historical growth and market overview
In a broad sense, the requirement for smoke ventilation and control in buildings goes back to when fire was first brought inside buildings for cooking and heating. Over the centuries, this smoke control approach has become more sophisticated by engineering and adding chimneys, flues and fireplaces. It wasn’t until the industrial revolution in the 19th century (leading to the construction of high-rise buildings) that smoke ventilation became vital to the safety of the residents of these buildings within towns and cities. Whilst steps were taken to regulate smoke ventilation in the early 20th century; it wasn’t until the 1960s and ’70s that decisive steps were taken in developing smoke ventilation in the UK and North America by the NRCC and BRE. Research and development of smoke-control technology have been conducted worldwide and performed in many countries (Canada, England, France, Japan, United States, Germany and recently GCC and the Middle East). The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) published a design manual for smoke-control systems (Klote and Fothergill, 1983). This ASHRAE Smoke Control Manual was the first document on the subject specifically intended for use by designers.
The smoke ventilation and control system has witnessed considerable growth and recently received more global attention due to the greater understanding and knowledge of the dangers of smoke to occupants. In 2020 the global fire-rated duct market size was reported to be USD 2,212.1m. Fortune Business Insights projected growth from USD 2,280.3m in 2021 to USD 3,165.3m by 2028 at a compound annual growth rate (CAGR) of 4.8%.
A recent report by research firm 6W Research revealed that the market for fire prevention and safety equipment and systems in the Middle East will grow at a CAGR of 2.6% until 2025, with a cumulative value of USD 2.3bn. The report indicated that the United Arab Emirates, Turkey and Saudi Arabia would represent the main drivers of this growth, given that the market value is currently USD 1.96bn.
Technical overview
Smoke can adversely affect people, property (including the building structure and contents) and mission continuity. The effect of exposure to smoke depends on the magnitude of the properties of the smoke (concentration of various gases, visibility reduction, temperature, and radiant flux) and the duration of the exposure. People exposed to smoke may be harmed due to exposure to toxic gases, elevated temperatures, or radiant energy. That is why the smoke control and management systems have received more attention lately, and therefore the smoke control ducts.
Generally, ductwork transfers many kinds of air and gases from one location to another. Usually, the duct is associated with air conditioning systems, fresh and exhaust air systems, heated air application systems and smoke-control systems. To categorise the ducts, as per the fire-protection purpose with the working system association, the duct can be classified as follows:
- Non-fire-rated duct with ventilation system: these serve as a heating, ventilation and air conditioning (HVAC) system duct, and it is not required to be assessed against fire-resistant performance. It can also be occupied with fire dampers.
- Fire-rated duct with ventilation system: these serve as a heating, ventilation and air conditioning (HVAC) system duct, and it is required to be assessed against fire-resistant performance when the design requires HVAC systems to be running during the event of a fire (for example in a health care building where there are needs for air handling unit(s) during an incident of fire).
- Duct for smoke-control systems and heated air and gas application systems: according to the design requirement, these systems usually happen with a fire-rated duct. For the smoke-control and management system, the duct transfers the smoke out of the building and, in some design detail, is required to bring make-up air to the building.
This article discusses the duct for smoke-control systems and heated air and gas application systems identified above.
Design
All design documents plead to protect the building, occupants, firefighters and smoke-control system against smoke and fire spread by guiding the smoke-control-system designers to select the right plan with consonant components. One of the featured documents for the smoke control and management system is Handbook of smoke control engineering by John H. Klote, editor and chief, James A. Milke, Paul G. Turnbull, Ahmed Kashef, Michael J. Ferreira. Whether the smoke control and management systems work by the natural flow of the smoke through the openings and ducts or are mechanically driven throughout the system, or whether the plans are triggered by an electrical signal or by mechanical inductance, the design documents required the system’s ducts to be assessed working under fire conditions.
Smoke can be controlled by extracting from the place of the origin – under negative pressure – (for example, in the building corridor) or by keeping it from entering the protected area – under positive pressure – (for example, in the building staircase) or by maintaining the compartmentalisation inside the duct system (for example, closing the smoke damper inside the duct to protect the adjacent areas from the smoke spread). The smoke dampers control the smoke flow through the system’s duct, and the smoke and fire dampers come to block the smoke and fire spread if required. Contrary to common understanding, the fire-rated duct is incompatible with fire dampers, and this is due to the work nature under fire conditions for the fire-rated duct.
There are several ways to design smoke control and management systems. Still, some designs or applications may cause danger to the building if the selection and application of the system’s duct is not appropriately handled and because the duct of the system typically goes throughout the building, penetrating the building compartment fire barrier(s), which poses the risk of fire and smoke spreading. Therefore, these systems must be designed and implemented with care and attention.
Fire resistance rules and regulation
Characteristically the design documents require the components of smoke control and management systems to be assessed working under fire or heat conditions. In addition to the design documents, the regulations and legislation of the Authority Having Jurisdiction (AHJ), which in this region is typically the Department of Civil Defence (CD), is tasked to organise and legislate requirements for fire-rated ducts towards ensuring that buildings achieve a certain level of fire and smoke protection.
All the various regulations throughout this region align and provide provisions that ductwork must be fire-resistive proven when it passes through the fire-rated compartment to prevent compartment fires from spreading into another compartment or out of the room of origin through the ductwork. Depending on the fire-protection-based design and prescribed regulations, the required fire rating and performance criteria may differ from AHJ to AHJ throughout the various regions.
Documents like the International Building Code (IBC) and International Fire Code (IFC) were published by the International Code Council (ICC). The I-Codes are the basis of laws and regulations in communities across the U.S. and other countries (e.g. Saudi Arabia International Building Codes). Also, Approved Document B in the UK’s English building regulations gives practical guidance about how to meet the building fire safety regulations requirements for England. These documents are often considered legislation and regulation sources of fire-rated ductwork criteria (integrity, stability, insulation) and acceptable standards of performing these criteria.
All the authorities worldwide are gravitating toward adopting the renaissance in the smoke control field. The United Arab Emirates (UAE) is at the forefront and leads the various countries throughout this region with good codes, standards and regulations. The UAE Fire and Life Safety Code of Practice (UAEFLSC), which comes with a broad and comprehensive solution for fire and life safety applications for buildings in the UAE, has devoted an entire chapter to smoke control and management systems in chapter 10. This chapter covers the requirements for smoke control and smoke management systems and requires satisfying the criteria of stability, integrity and insulation for smoke-control ducts.
Many legislators agree on these criteria for smoke control ducts, even if the criteria terms differ. Usually, the smoke control duct is verified under fire conditions for the following:
- Integrity: The duct must withstand fire conditions without allowing the fire to spread from inside to outside or vice versa through openings, cracks, holes.
- Stability: The duct must continue functioning as intended during the fire conditions without collapse or loss of shape (unless the acceptable limit by standards).
- Insulation: The duct must not spread the fire through radiant heat from duct service. Therefore, the duct must be capable of insulating the inside and external duct conditions.
Testing and certification
Fire represents an enormous danger to life, property and the environment, making verifying the performance of fire-protection-system components in fire conditions essential.
Ductwork for smoke-control systems (both extract and make-up air ducts) is required to be assessed against specific standards determined by the AHJ; standards like (BS 476-24, EN 1366-8, EN 1366-9, ISO 6944, …etc.) are widely accepted across the GCC and Middle East region. Usually, testing and certification standards objectives cover one or more of the following: fire conditions test (direct fire test or heat condition test), operational test, classification requirements, product requirements, or fields of application (direct or extended).
As discussed above, there are three performance criteria that these ducts are evaluated against: integrity, stability and insulation. The region’s local authorities mandate and require the designer, specifier and installer to provide smoke-control ductwork systems that have had their fire testing performance evaluated against two criteria – integrity and stability. These must be certified and listed by a recognised certification or conformity assessment body (CAB). The third performance criterion – insulation – is required only if the ductwork path of installation passes through more than one fire compartment.
There has been to date common confusion and misunderstandings regarding these criteria in the local and regional markets, like:
- Difference between ventilation fire-rated duct type and smoke control duct type: It is easy to confuse these two types. But the primary concern of ventilation fire-rated ducts under fire conditions is not to spread the fire. While the main problem for smoke-control ducts is to be functional (smoke extraction or make-up air) and not to spread the fire during a fire incident.
- System insulation criteria and stand-alone insulation criteria: Satisfying insulation criteria for stand-alone insulation nor testing the insulation with different temperatures other than the entire fire scenario does not present insulation criteria for the smoke-control duct system.
- Ductwork test temperature: Some ducts are tested for a single compartment (or in the UK for a specific type of car parking structures in England) with less test rig furnace temperature than the prescribed following the fire test standard required time-temperature curve, which is not compliant with these regions’ prescribed fire test method required time-temperature curve scenario as discussed above for a multi-compartment application and use.
For example, the UAE and GCC markets have previously witnessed this misuse and malpractice (per our regional prescribed requirements), which has since been re-evaluated, reviewed, corrected and controlled by the governing authorities. Here, the conscious and responsible role of the conformity assessment bodies must help the AHJ be aware, understand and assist in confronting such challenges by working competently to issue certificates and conformity following the local principles, regulations and laws, or as a minimum to clearly state the reduced performance(s), where ductwork test temperature has been modified and reduced, within the testing evidence and listing certificates, and in the UAE, only issuing a UAE Certificate of Compliance (CoC) per the provisions of the UAEFLSC, which does not allow this reduced ductwork test temperature to be modified and reduced.
The local markets in the region are witnessing broad enlightenment and excellent awareness in the fire-protection field. This guides the general market mood for the legislators, installers and end users towards the correct applications of fire-protection systems, as they significantly impact life and property. From this standpoint, the Dubai Civil Defense (DCD) initiative was born to establish the Emirates Safety Laboratory (ESL) to test and certify passive fire products and systems and fire-protection systems and their components. ESL is the region’s first government fire-testing laboratory and has comprehensive testing and certification solutions for almost all fire-protection products and systems (development is taking place in the laboratory at a high rate). ESL currently has over 90 test methods in its facility and can certify more than 600+ test methods. Concerning smoke-control ductwork, the laboratory is the first in the GCC, Middle East, North Africa (MENA) and South Asia to carry out tests related to this product category. The laboratory is staffed with a sizeable team consisting of local and internationally experienced technical experts to meet the needs of regional and other international markets. Invariably, the ESL precept is ensuring a safer and sustainable future together.
About the Author
Mohammed Hassan
Mohammed Hassan is a Mechanical Engineer and Certification Specialist with Emirates Safety Laboratory. Over the last 14 years, he has specialised in smoke management and passive fire protection systems. He is a Certified Fire Protection Specialist and also recognised by ASHRAE as a Certified HVAC Designer and, per GREEN BUSINESS CERTIFICATION, as LEED AP BD+C.
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