Sources and scope for this page: Industry convention — no single governing standard (conventional usage, definitions vary between sources), covering the definition of ul 94 flammability rating. No independent source check is recorded for this page: the content rests on the sources listed and on the working shown on the page. How sources, methods and updates are recorded.
Definition
The ratings run HB (horizontal burn, the weakest), V-2, V-1, V-0 (vertical, self-extinguishing, with V-0 the best) and 5VA/5VB for the most demanding applications.
The rating is thickness-dependent — a material rated V-0 at 3 mm may be only V-2 at 1.5 mm. Quote the thickness with the rating; a bare "V-0" is incomplete.
Common misuse
Quoting a UL 94 rating without its thickness. The same material can have different ratings at different wall thicknesses.