Optional “L-Rating” (Smoke seal) with Firestik™
UL provides an optional “L-rating” which can be measured and assigned to individual assembly penetrations or joints. The L-rating simply defined for a joint is a measurement of the air leakage rate through a fire stop system or fire-resistive joint system without fire exposure, tested under a differential pressure of 0.30 inches water column (75 Pa) at both 75 and 400 degrees Fahrenheit. It is expressed as a volumetric flow rate in units of cfm/lft.
Measurements taken of assemblies utilizing either slotted or solid leg tracks and using Firestik HOW joint fire stop protection established L-ratings for Firestik. Tested “severe condition” assemblies were installed perpendicular to a 3” deep fluted pan deck having only a 4pcf mineral wool compressed 33% into the flute, no mastic covering per UL listed Firestik assemblies, no insulation materials inside wall cavities or HOW gap, and cycled 500 times at level III (30 cycles/min) movement.
The results reflected in UL listings:Slotted Track
- Slotted track with 1 ½” slots centered on 2 ½” legs spaced 1” O/C
- HOW joint cycled and opened full 1”
- FS1 (Firestik for 1” deflection) installed both sides
L-rating at 400deg. F = Less than 1 CFM/lft
Solid leg track
- Single track with 2 1/2” solid legs
- HOW joint cycled and opened full 2”
- FS2 (Firestik for 2” deflection) installed both sides
L-rating at 400 deg F = Less than 1 CFM/lft
Results of UL “L-rating” tests show assemblies utilizing Firestik fire-resistive joint protection for up to level III movement achieve the lowest ratings possible for air leakage protection well below the IBC standard of 5 CFM/lft.