Flammability is the ability of a substance to burn or ignite, causing fire or combustion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. 

UL 94

UL 94, the standard for safety of flammability of plastic materials for parts in Devices and Appliances testing. There are two types of pre-selection test programs conducted on plastic materials to measure flammability characteristics. The first determines the material’s tendency either to extinguish or to spread the flame once the specimen has been ignited.

There are 12 flame classification specified in UL 94 that are assigned to materials based on the results of these small scale tests. These classifications listed in descending order for each of the following three groupings are used to distinguish material’s burning characteristics after test specimens have been exposed to a specified test flame under controlled laboratory conditions. 




Flame Classification

Flame Name


Manufacturing enclosures, Structural parts and insulators found in consumer electrical products.


5VA, 5VB, V-0, V-1, V-2, HB


Low density foam materials commonly used in fabricating speaker grills and sound deadening material.


HF-1, HF-2, HBF


Very thin films. They are usually assigned to substrates on flexible printed circuit boards


VTM-0, VTM-1, VTM-2