Understanding UL94 Flame Ratings

What are the UL94 Flammability Tests?

The UL94 flammability tests offer a preliminary indication of a plastic material’s usability in certain devices or appliances.​

These tests use standard specimens and are conducted under predefined conditions. They compare the relative burning characteristics of​ different materials, assessing any changes that may take place during use in their intended application.

A UL94 rating is not intended to reflect the hazards of a material under actual fire conditions.

5VA Surface Burn

This test involves applying a flame to a bar of test material for five seconds, five separate times. The test material must stop burning within 60 seconds and cannot develop a burn-through hole. Passing this test earns a material the highest, most flame-retardant UL94 rating.

5VB Surface Burn

This rating test involves applying a flame to a bar of test material for five seconds, five separate times. The test material must stop burning within 60 seconds, but it is allowed to develop a burn-through hole.

V-0 Vertical Burn

To pass this test, a material must stop burning within ten seconds after a flame is applied to it twice (for ten seconds each time). In addition, no flaming material drips can occur.

V-1Vertical Burn

To pass this test, a material must stop burning within 60 seconds after a flame is applied to it twice (for ten seconds each time). No flaming material drips can occur.

V-2 Vertical Burn

To pass this test, a material must stop burning within 60 seconds after a flame is applied to it twice (for ten seconds each time). Unlike V-0 and V-1 tests, flaming material drips are allowed.

HB Horizontal Burn

In this test, material must display a horizontal burn rate of less than 3" per minute — or stop burning altogether before 5” of the material test bar catch fire. HB-rated materials are considered “self-extinguishing.”​