UNDERWRITERS LABORATORIES 94HB:
Test is run with bars one half inch wide by five inches long. These are held horizontally and exposed to a laboratory burner flame three quarters of an inch high. Ignition is forced until one inch of the sample has burned, the flame removed, and the burning rate measured.
To Pass ULHB: A sample over one eighth inch thick must burn slower than one and one half inches per minute and a sample one eighth inch thick or less must not burn faster than three inches per minute. This is very similar to DOT MVSS 302.
UNDERWRITERS LABORATORIES 94-V:
Test is run with bars one half inch wide by five inches long. These are held horizontally and exposed to a laboratory burner flame three quarters of an inch high. Each sample is ignited for ten seconds, the flame allowed to go out, and ignited again for a second time of ten seconds. The time taken for the flame to go out is measured and the technician watches for burning char or liquid droplets falling.
To Pass UL94V-0 flame must be out in ten seconds or less, no glow beyond thirty seconds, and no burning material can fall.
To Pass UL94V-1 flame must be out in thirty seconds or less, no glow beyond sixty seconds, and no burning material can fall.
To Pass UL94V-2 flame must be out in thirty seconds or less, no glow beyond sixty seconds, and burning material can fall.
UNDERWRITERS LABORATORIES 94-V:
This is a newer and tougher version of the UL 94 V test. The sample size stays the same for the first part of the test, but the flame size increases to five inches from three quarters of an inch and the number of ignitions increases from two to five but the duration is decreased from ten to five seconds.
Along with bars a test piece six inches by eight inches is mounted horizontally and the bottom center is exposed to five, five-second flame exposures five seconds apart.
To Pass UL94-5VA the flame and glow must be out in sixty seconds or less, no burning material can fall, and the flame cannot penetrate the six by eight inch panel.
To Pass UL94-5VB the flame and glow must be out in sixty seconds or less, no burning material can fall, but the six by eight inch panel can be penetrated.