What are the fire retardant levels of insulation sheet?

There are multiple classification systems for flame retardant levels, and the following are some common classifications:

UL94 flame retardant rating

-V-0 level: After two 10 second combustion tests on the sample, the flame will extinguish within 10 seconds and the droplets will not ignite the degreased cotton.

-V-1 level: After two 10 second combustion tests, the flame will extinguish within 30 seconds, and the droplets will not ignite the degreased cotton.

-V-2 level: After two 10 second combustion tests, the flame will extinguish within 30 seconds, and droplets will ignite the degreased cotton.

-HB level: horizontal combustion test, for materials with a thickness of less than 3mm, with a combustion rate of less than 38mm/min; Materials with a thickness greater than 3mm have a combustion rate of less than 76mm/min.