ò Class A or Class 1 =
A flame spread rating of < 25
á
and a smoke developed number of < 450
ò Interior Type A = An
FRTW must remain at or
á
below 28% moisture content when conditioned at
á
92% relative humidity and 80oáF to be within
á
hygroscopic limits.
ò FR-S = If an FRTW
product has both a flame
á
spread and smoke developed number of < 25 and no
á significant progressive combustion in a 30
minute test,
á
it shall bear this designation. If the smoke developed
á
number is higher, both the flame spread and smoke
á
developed number must be specifically stated on the
á
wood and it loses the FR-S designation.