Grease management ranks at the top of the list when it comes to kitchen safety. Grease is a universal concern because buildup in a hood or vent system can lead to quick-spreading fires that are difficult to extinguish. That is why fire test standards are designed to replicate expected real-life fire conditions and have undergone serious transformations.

In January 2009, Underwriters Laboratories (UL), Intertek Systems and the International Code Council (ICC) Evaluation Service mutually abandoned all listings or evaluations that are based on Southern Building Code Congress International Inc. (SBCCI) and Building Officials and Code Administrators (BOCA) acceptance criteria. Both codes used the internal fire test portion of UL1978, which addresses reduced clearances for field-applied flexible wrap systems. Today, the only listing for flexible wraps applied to grease ducts is the American Society for Testing and Materials (ASTM) E2336-04.

These changes affect the commercial foodservice industry significantly and directly impact architects, engineers, specifiers and contractors. It's imperative that foodservice consultants recognize and address these changes early on to avoid widespread confusion and potentially major project redesign, delays or additional costs.

History of Grease Duct Codes

Essentially, three primary code bodies regulate the installation of grease ducts for commercial kitchen applications: the National Fire Protection Association (NFPA), the International Mechanical Code (IMC) and the Uniform Mechanical Code (UMC). These model codes specify standards and listings developed by independent testing groups such as UL and ASTM International.

Despite the fact that grease duct systems have been around for decades, guidelines for test procedures weren't identified until 1995, when UL 1978 was introduced. However, UL 1978 was not specifically a fire test standard, but more of a comprehensive standard for evaluating and listing factory-built grease ducts.

As alternatives to traditional rigid shaft enclosure construction became more popular and through the emergence of a national model code body (ICC), it was apparent that instituting a national fire testing standard was necessary. Consequently, the ASTM E2336 test standard was created to evaluate grease duct enclosure systems. Criterion specifically mandates that the building construction community recognize the requirements of the new standard for fire-resistant grease duct systems and adapt its design accordingly. The ASTM E2336 standard was first published in April 2004 and is titled Standard Test Methods for Fire-Resistive Grease Duct Enclosure Systems.

Grease Duct Enclosure Systems

Previous building codes allowed limited options only for fire-resistant grease duct enclosure systems to be used in commercial kitchens, and the majority required some type of rigid board material. Traditional shaft construction is built from fire-rated gypsum or calcium silicate board materials and has historically been deemed an internal fire risk. However, alternative grease duct enclosure systems, such as fire-resistant flexible-wrap materials, have gained significant credibility over the years for use in exhaust ducts. The flexible-wrap material offers zero clearance to combustibles and can contain grease duct fires while saving building space and labor costs.

Simply put, UL 1978 was the best existing standard solely because it was the only one available during the time new flexible enclosure materials were being considered. Flexible-wrap grease duct enclosure systems should gain even more popularity now that all the major model codes in the United States clearly reference a specific testing standard—(ASTM) E 2336—to show compliance.

Safety First

Numerous factors affect how an actual kitchen fire is going to behave in a real-life situation. Ultimately, fire test standards evaluate products against expected fire conditions and provide the foodservice community with affirmation that the equipment being used is safe for that particular application. The ASTM E2336 code subjects grease duct enclosure systems to five different fire tests. These distinct trials reveal important characteristics of the enclosure system.

• Section 4.1 ensures that the enclosure material does not add significant fuel to a fire during the evaluation period.
• Section 4.2 can be described as a fire resistance test. This rigorous test is designed to simulate a building fire external to the duct and to determine whether the external fire can potentially ignite the combustibles within the duct.
• Section 4.3 ensures the enclosure material does not change over time when subjected to normal elevated temperatures found near operating grease duct exhaust systems.
• Section 4.4 can be described as an internal fire test, which requires that an elbow-shaped grease duct with both a horizontal and vertical component be subjected to four hours of 500-degree Fahrenheit temperatures and 30 minutes of 2,000-degree Fahrenheit temperatures. This test establishes that materials placed directly against the enclosure system will not combust and determines if the system will have zero clearance.
• Section 4.5 tests the integrity and stability of the duct through the duration of a one- or two-hour rating period by subjecting the grease duct to an external fire engulfment defined by ASTM E119.

These tests are much different from the criteria previously based on UL 1978. Specifically, the internal fire test is more specific, more repeatable and more difficult for enclosure systems to pass. Additionally, the portion in ASTM E2336 (defined in Section 4.2) regarding fire resistance is a completely new requirement from those previously specified by testing labs.

Because these tests are significantly different from UL 1978, the flexible-wrap-type enclosure systems that are currently available meet all five criteria of ASTM E2336 and are all applied in a minimum of two insulation layers. In fact, most of the two-layer systems available today are made out of a thicker, heavier insulation material than that used in the previous single-layer system that met criteria based on UL 1978. Therefore, it is important that specifiers, contractors and inspectors look for systems that not only have met all the requirements of ASTM E2336, but also are thinner, lighter, more flexible and have installation advantages.

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