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Printed circuit board with the mark "94V-0" in the bottom-left corner

UL 94, the Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing, is a plastics flammability standard released by Underwriters Laboratories of the United States.[1] The standard determines the material's tendency to either extinguish or spread the flame once the specimen has been ignited. UL-94 is now harmonized with IEC 60695-11-10 and 60695-11-20 and ISO 9772 and 9773.[2]

The VW-1 (vertical wire burn) rating is sometimes erroneously associated with UL 94, but it (and some other flammability tests) is described by UL 1581 (Reference Standard for Electrical Wires, Cables, and Flexible Cords).


From lowest (Least flame-retardant) to highest (Most flame-retardant):


Tests are generally conducted on a 5 × 12 in (127 × 12.7 mm) specimen of the minimum approved thickness. For 5VA and 5VB ratings, tests are performed on both bar and plaque specimens, and the flame ignition source is approximately five times as severe as that used for testing the other materials.

Foam and films

This section needs expansion. You can help by adding to it. (May 2015)

There are other classifications that apply to low density foam materials (HF-1, HF-2, HBF) and thin films (VTM-0, VTM-1, VTM-2).

See also


  1. ^ "UL 94, Tests for Flammability of Plastic Materials for Parts in Devices and Appliances". UL. Retrieved 1 December 2021.
  2. ^ "Combustion (Fire) Tests". UL. Retrieved 1 December 2021.