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UL94 standard flammability tester


UL94 standard flammability tester

What is UL 94 ASTM standard?

The UL 94 standard is a flammability of plastic materials used in devices and appliances. It is published by Underwriters Laboratories (UL) and often referenced alongside ASTM (American Society for Testing and Materials) standards, specifically ASTM D635, ASTM D3801, and ASTM D4804, which are similar in nature.

Difference between UL94 and CSA


To evaluate the flammability of plastic materials, ensuring they meet safety standards for use in electrical devices and appliances.

Test Methods:


The UL 94 standard includes several test methods to assess how materials react to flames. The primary test methods include:

  • Horizontal Burning Test (HB):

Materials are classified based on their burning rate in a horizontal orientation.

HB rating is the least stringent and typically indicates that the material burns slowly in a horizontal position.

  • Vertical Burning Test (V-0, V-1, V-2):

Materials are classified based on their burning behavior in a vertical orientation.

V-0 rating: Stops burning within 10 seconds with no flaming drips.

V-1 rating: Stops burning within 30 seconds with no flaming drips.

V-2 rating: Stops burning within 30 seconds with flaming drips allowed.

  • Vertical Burning Test for Thin Materials (VTM-0, VTM-1, VTM-2):

Similar to the vertical burning test but designed for thin, flexible materials.

VTM-0, VTM-1, and VTM-2 classifications follow similar criteria as V-0, V-1, and V-2 but are specifically for thin materials.

  • 5V Test (5V-A, 5V-B):

More stringent vertical test for materials that can stop burning within 60 seconds after five applications of a flame.

5V-A rating: No flaming drips and no hole formation.

5V-B rating: No flaming drips but holes are allowed.

Materials are classified into one of the UL 94 ratings based on their performance in these tests. The ratings help manufacturers choose appropriate materials based on the required flammability resistance for their applications.

ASTM Standards Related to UL 94

1.ASTM D635: Standard Test Method for Rate of Burning and/or Extent and Time of Burning of Plastics in a Horizontal Position.

2.ASTM D3801: Standard Test Method for Measuring the Comparative Burning Characteristics of Solid Plastics in a Vertical Position.

3.ASTM D4804: Standard Test Method for Determining the Flammability Characteristics of Nonrigid Solid Plastics.

4.These ASTM standards complement the UL 94 standard by providing additional methods and criteria for evaluating the flammability of plastic materials.

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