The aim of the test is to classify the materials according to their flammability. UL 94 consists of two test types: vertical and horizontal. It was introduced by Underwriters Laboratories.
Horizontal testing – HB The test is carried out for 13mm thick samples. The matirial is tested in a horizontal position and subjected to a flame at 20mm distance for 30 seconds (or till the flame reaches 25mm marker) at an 45°angle
UL 94 HB is assigned on the basis of burning rate of given samples according to the following criteria:
for 3mm-13mm samples – burning rate does not exceed 40mm/min at 75mm distance; for samples thinner than 3 mm – burning rate does not exceed 75mm/min at 75mm distance; a sample stops burning before the flame reaches 100mm on the scale
Vertical testing 94V-0, 94V-1, 94V-2) The material is tested in a vertical position and subjected to a flame at 20mm for 10 seconds (twice). Testing criteria: burning time, total burning time, sample parts which fell during burning. The table prestents critera used in assigning flammability.
Criterium |
94V-0 |
94V-1 |
94V-2 |
burning time after each flame application |
≤ 10 s |
≤ 30 s |
≤ 30 s |
Total burining time per sample (10 flame applications) |
≤ 50 s |
≤ 250 s |
≤ 250 s |
burning and glow time after the second flame |
≤ 30 s |
≤ 60 s |
≤ 60 s |
cotton wool ignition |
No |
No |
Yes |
Vertical Testing 94-5VA, 94-5VB
Longitudinal and narrow samples are positioned verticaly. They are subjected to the flame 5 times for 5 seconds with 5 seond break. Samples in the shape of boards are subjected to the same test, however they are positioned horizonatly and the flame is directed at the bottom side of the board. In both samples the flame is at 20° angle.Below the samples the cotton wool is placed. Criteria for the test:
Criterium |
94-5VA |
94-5VB |
burning and glow time after 5 flame aplications (narrow samples) |
≤ 60 s |
≤ 60 s |
cotton wool ignition |
No |
No |
burning and glow time after the second flame |
No |
Yes |
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