L RATING
An air leakage rating used to
measure and limit the airflow and
thus the smoke leakage through
a firestop system. The L rating
provides a quantitative indica-
tion of the through-penetration
firestop system’s ability to resist
the passage of smoke. Only the
penetrations and joints in smoke
barriers (Sections 714.3, 714.4.4
and 715.6) are required to have
an L rating and meet the code’s
limits on air leakage. While pro-
visions for protecting penetra-
tions for fire performance have
been included in the IBC since
its first edition
(and were included in each of
the three legacy codes), L rat-
ing requirements were included
for the first time in the 2006 edi-
tion. Therefore, buildings built
according to the earlier codes
would not have been required to
be provided with L ratings. How-
ever, some penetration firestop
systems installed within them
may have been provided with
this level of protection. L rating
is measured in cfm/sq. ft.
L Rating requirements are yet to
be included in NBC.
W RATING
Although not currently required
by the code, it is important to un-
derstand this term since some
firestop systems indicate that
they are listed with a W rating.
Code users should be familiar
with this term since there may
be situations where the owner
or designer desires this level of
protection.
The W rating is a water leakage
rating used to demonstrate that
a firestop system will prevent
water leakage through the sys-
tem, and will maintain its fire
performance after incidental wa-
ter exposure. The water leakage
evaluation is done using a 3-foot
water column pressure head for
72 hours.