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It’s so hot here!

Let’s be thankful for air ducts, says Dwayne Sloan

| | Nov 18, 2019 | 5:21 pm
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The Middle East is known for many things – but one unmistakable characteristic of the region is the year- round warm temperatures. So, we will take a moment to appreciate air conditioning, ventilation, air ducts and the products that seal them. There are millions of feet of factory-made air ducts installed in residential and commercial buildings, worldwide. From the hottest summers in this region, to the coldest winters in cold regions, these unsung heroes deliver tempered air just for our comfort.

Around the late 1950s, primarily in North America, the predominant means of delivering comfort air was through sheet metal air ducts. When alternative air duct types were being considered, such as factory- made rigid fiberglass air ducts, spirally wound metal ducts and flexible (wire helix) air ducts, the governing building regulations needed
a way to demonstrate that these products possessed the adequate fire performance, material construction, and structural integrity for safe and effective use within buildings.
UL worked diligently with the regulatory community, air duct industry and the sheet metal duct industry to publish the very first Standard on this topic, UL 181, Standard
for Safety Factory-Made Air Ducts and Connectors, which was released in 1961.


Today, eleven editions of the Standard later, most major codes – such as IBC, IMC, IRC, NFPA 90A, NFPA 90B, NFPA 5000, UMC, UAE FLS and KSA SBC 5011 – require commercial and residential factory-made air ducts to comply with ANSI/UL 181. This Standard challenges air ducts to a full range of rigorous tests before the designs are acceptable for use. The below is a summary list of tests from UL 181 for rigid and flexible factory-made air ducts:

In the mid-1990s, it was recognised that the products that attach and seal air ducts also needed their own dedicated set of requirements. UL worked with industry to develop UL 181A – Standard for Closure Systems for Use With Rigid Air Ducts and UL 181B – Standard for Closure Systems for Use With Flexible Air Ducts and Air Connectors, applicable to tapes, mastics and non-metal fasteners. More recently, specific air duct types, such as phenolic rigid air ducts, have become prevalent in the region. It is UL’s experience that the insulation component of these air ducts plays an important role. We find that products such as phenolic and fibreglass have burning characteristics that allow the overall duct constructions to comply with the rigours of UL 181. Conversely, in our experience, insulations such as polyurethane foams do not allow the overall duct constructions to comply with the flammability requirements of the Standard.

In addition, UL has created new Outlines and Standards for fabric dispersion ducts, aerosol-sprayed duct sealants and sheet-metal ducts with pre- sealed ends.


The current UAE Fire and Life Safety Code (2018), Chapter 10 requires factory-made air ducts to be Class 0 or Class 1 and listed in accordance with ANSI/UL 181.

Listing and labelling of these air ducts demonstrates an ongoing commitment to safety and quality. Air ducts comprise several materials assembled together as a composite. The listing and labelling programme demonstrates that the complete composite assembly – the insulation, adhesive, facing and more have been evaluated.

Certification with UL means a product has been evaluated, complies with UL’s requirements, and is manufactured under a follow-up programme, meaning the certification extends beyond testing. This programme allows UL to verify that products remain compliant with requirements and are produced in a manner representative of the construction of the product that was originally evaluated and certified. UL’s Listing Mark on air ducts and their closures is the manufacturer’s representation that samples of that product have been evaluated to the rigours of UL 181, UL 181A and UL 181B, as applicable.

While the primary objective of the Civil Defence and the implantation of the UAE Code is to ensure safety of life and property, it is recognised that product manufacturers, building owners, architects, consultants and other stakeholders share in this responsibility. Chapter 18 of the UAE Fire and Life Safety Code addresses these responsibilities of stakeholders. Assuring that air ducts bear a third-party certification label and that they are installed in accordance with the accompanying manufacturers installation instruction is important to ensure that the products installed are under a follow-up programme and have been found to comply with applicable requirements.


UL will be hosting a two-day seminar, titled “Meeting the Safety Challenges of the Built Environment” on December 18 and 19, 2019 at the Sofitel Dubai, Jumeirah Beach, UAE. The seminar will focus on fire- resistive ducts, ventilation ducts, exterior wall systems and UL’s
Field Engineering Services. Besides UL, participants include the Civil Defence, manufacturers, architects and many others. For more information, contact UL.MENA@ ul.com.


Dwayne Sloan is Director of Principal Engineers and Regulatory Services at UL. He can be contacted at UL.MENA@ul.com.


  • IBC – International Building Code
  • IMC – International Mechanical Code
  • IRC – International Residential Code
  • NFPA 90A – Standard for the Installation of Air-conditioning and Ventilating Systems
  • NFPA 90B – Standard for the Installation of Warm Air Heating and Air-Conditioning Systems
  • NFPA 5000 – Building Construction and Safety Code
  • UMC – Uniform Mechanical Code
  • UAE FLS – UAE Fire and Life Safety Code of Practice
  • KSA SBC 501– Saudi Mechanical Code

CPI Industry accepts no liability for the views or opinions expressed in this column, or for the consequences of any actions taken on the basis of the information provided here.

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