What do the UL Systems Data Letters Stand For?

The first letter of the listing designation identifies the type of penetrated fire-rated structure:

C for both floor and wall penetrations
F for floor penetrations only
W for wall penetrations only

The second letter designation identifies the construction type:

A for concrete floors less than or equal to 5 inches thick
B for concrete floors greater than 5 inches thick
C for framed floors
D for deck construction
J for concrete or masonry walls less than or equal to 8 inches thick
K for concrete or masonry walls greater than 8 inches thick
L for framed walls
M for bulkheads

Flame: The “F” rating is expressed in hours. This number indicates the specific length of time a barrier can withstand fire before being consumed or before permitting the passage of flame through an opening.

Temperature: The “T” rating is expressed in hours and indicates the length of time the temperature on the side of the penetration without fire does not exceed 325 F above the ambient temperature. This ensures the temperature on the side of the wall away from the flame does not reach the flash point of any materials on that side of the wall.

Smoke: The “L” rating is the amount of air (smoke) that can leak through a penetration, measured in cubic feet per minute. The test is administered at ambient temperature and at 400 F to determine the actual performance of fire-stopping materials at different temperatures.

Water: The “W” rating, established in 2004, indicates the fire-stopping material has passed the UL test for water tightness. The Class One requirements for water tightness include subjecting the material to a 3-foot water column for 72 hours, followed by a fire and hose stream test, conducted in accordance with ANSI/UL 1479. A Class Two listing requires the material to be resistant to a 20-foot water pressure head. Finally, a Class Three listing requires the material to be resistant to 57.54-foot water pressure head. According to one of its spokesmen, UL developed the new “W” rating to prevent water damage and mold-friendly moisture associated with through penetrations.