FRTW Wood Is:
Lumber and plywood that is pressure impregnated with a fire retardant chemical to reduce the spread of flames, smoke development and shows no significant progressive combustion within a 30 minute test.
Is there a difference between FR coatings and FRTW?
Yes. FR coatings are
tunnel tested for a time period of 10 minutes, opposed to FRTW which
is tested for 30 minutes.