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Asia On The Mark Issue 23 (Fall 2007)

UL 94: The Misunderstood Fire Test
Building owners, architects or contractors sometimes run across UL 94 rated materials that they think might be used in a model code application, and submit them for AHJ approval. In fact, model codes do not recognise the small-scale UL 94 fire ratings such as HB or V-0, and there is no technical basis for accepting a UL 94 rating in lieu of other ratings specified in the Codes.

Therefore, let's shed some light on what the UL94 Standard and its associated flammability ratings are and, more importantly, what they are not.

Model building, life safety and fire codes include numerous requirements that products and materials include specified minimum flammability ratings. Among other things, this includes tests to determine the following:


Hourly fire resistance ratings


Surface burning characteristics of interior finish materials (flame spread and smoke developed


Roof covering flammability ratings


Flammability of contents within the building (such as mattresses, furniture, fabrics or floor coverings)


Stored commodity classification

  UL 94: The Misunderstood Fire Test

Although the test methods and desired fire performance vary between tests, they have a common underlying principal behind them, namely that (1) a relatively large amount of the material is likely to be present, (2) the ignition source for the material may consist of a fairly substantial open flame or radiant energy source and (3) the tests are primarily based on the end-use of the product. Accordingly the fire tests specified in the model codes often are referred to as medium-scale or large-scale fire tests.

UL 94, the Standard for Tests for Flammability of Plastic Materials for Parts in Devices and Appliances includes small-scale tests that evaluate the flammability of polymeric (plastic) materials, used for parts in devices and appliances, in response to a small, open flame or radiant heat source under controlled laboratory conditions. The scope of UL 94 clearly indicates that it does not cover polymeric materials used for building construction, finishing or contents such as wall and floor coverings, furnishings or decorative objects. The results of most UL 94 flammability tests are not applicable to materials whose thickness exceeds 13.0mm, or whose surface area exceeds 1m2.

The UL 94 Standard provides a method for rating the ignition characteristics of plastic materials. Two UL 94 ratings that code officials commonly run across are HB and V (V-0, V-1, or V-2). These ratings are established using small-scale tests in which approximately 5 by 1/2 inch samples are subject to a 3/4 inch, 50W tirrel burner flame ignition source. To achieve a HB rating, test samples, placed horizontally, burn slowly across the sample when the test flam is applied to the end of the sample. To achieve a V rating (e.g. V-2, V-1, or V-0) the test samples, placed vertically with the test flame impinging on the bottom of the sample, must extinguish withtin specified times, not burning to the top clamp or dripping molten material which ignites a cotton indicator.

UL has tested literally thousands of materials for UL 94 ratings, which are widely published in manufacturers’ literature. The customers for these materials are primarily the end-use manufacturers of electrical equipment and products that are required to use UL 94 rated materials in their factory production.

For additional information on UL 94 flammability ratings contact George Fechtmann at

In this Issue
Compliance effort on safe laptop for children
Korea Intelligent Robot Contest adopts UL Safety concept as criterion
UL sponsors Fire South China Expo 2007
UL leads discussion in regulatory risk issues at World Economic Forum
UL Standards to be used in Israel
China Wire & Cable industry united
OHSAS 18001: 2007
Trend for the Solar Photovoltaic Market and Product Certification
ENERGY STAR — Environmental label for electrical appliances
UL 94: The Misunderstood Fire Test
Dominic Ho elected to UL’s Board of Trustees
UL University
UL Standards
News Bites

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