What progress has the ducting industry made in terms of manufacturing techniques and processes, R&D, new features that support IEQ and energy efficiency, and in installation practices and maintenance? Tawfiq Attari at DuctSox Corporation examines some facts about UL Certification for fabric duct manufacturers

All fabric ducts and models made by any manufacturer should be tested with UL, says DuctSox Corporation, a manufacturer for fabric ducts around the world. The company says no one can test one fabric or one model and be UL certified for the other models. DuctSox, for example has a model called Sedona-Xm which tested under UL for L-Vent comfort flow. When the company manufactured the SG rubber diffuser, which is reportedly for high-throw applications, it did the UL for that model separately in order for it to be certified as fit to be used in buildings.

All fabrics should be treated with fire retardant, and that treatment should be tested to ensure it is permanent or inherently fire retardant, even after washing several times. If not, the material will not get a UL certification. Any material coated with fire retardant is not accepted for UL, and it will not have a UL stamp on its label. All the fabrics should be UL classified to UL2518 Standards, NFPA90A and ICC AC167.

Fabrics should meet the stringent fire-retardant requirements as dictated by independent organisations, such as Underwriters Laboratories UL2518, National Fire and Protective Agency NFPA90A and International Code Compliance Acceptance Criteria AC167 fabric.

The document, on the right, is a sample for online certification for UL. Any engineer can check this online to find out if they are certified for all of their material or only some of it.

UL Classified to be able to handle 747 Pa of Internal Static Pressure: in order to be certified to this level, UL requires that the fabric actually be tested and pass 2.5 times the published pressure. DuctSox says this means that its fabrics have actually been tested and passed Internal Static Pressures of 1,868 Pa.

The document below is the pressure test procedures in Section 10 of UL2518:

In this case, the manufacturer is UL Classified to 180°F. This is the only rating UL offers. In order to be certified to this temperature, UL Tests to 265°F. UL only tests and approves products down to 0°F.

The following is the temperature test procedure in Section 8 of UL2518:

The following table indicates maximum sectional length of a straight run. Longer sections are broken into equal lengths. The zippers are placed in order to ensure that the sections can be easily handled, installed and laundered, the company says.

The manufacturer should use reinforced stitching at all connections (straight runs, fittings, transitions and zippers) and seams. In addition, DuctSox says it incorporate double layers inlets, non-zipped and zipped removable end-caps and overlapping straps for zippers.