Horizontal burning test

UL 94 HB test trial arrangement

UL 94 HB test trial arrangement

The length of the test specimen is 5" (127 mm) and width 0.5" (12.7 mm). The test sheet cannot be more than 0.5 (12.7 mm) thick. Lines are marked on the sheet at the 1" and 4" locations. The sheet is fixed horizontally at one end and tilted 45 degrees in the direction of the width, as shown in the diagram. The burner used is adjusted so that it forms a 1" long blue flame. The flame is directed at an angle of 45 degrees to the front edge of the plastic sheet so that about 1/4 of the test specimen’s front edge is in the flame. The flame is applied for 30 seconds, after which it is removed. If the test specimen burns to the 1" line before 30 seconds have passed the flame is removed immediately. The test is carried out on three test sheets.

The material under investigation is classified as UL 94 HB  if, after the removal of the flame:


A) The speed of burning does not exceed 1.5" (38.1 mm) per minute when the  test specimen thickness is 0,120-0,500" (3,05-12,7 mm)

or

B) The speed of burning does not exceed 3,0" (76.2 mm) per minute when the  thickness of the specimen is less than 0,120" (3,05 mm)

or

C) Burning finishes before the flame reaches the 4" line

Copyright
Legal Notice