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Firestop Ratings
F-rating, T-rating and L-rating of firestopping systems
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All openings for electrical and HVAC applications in smoke-rated and fire-rated constructions must be sealed to resist the passage of heat, fire and smoke.
Firestopping systems are typically categorized by through-penetration of
- flames
- temperature
- smoke
Ratings according ASTM E814, "Fire Tests of Through Penetration Fire Stops" are
F-rating, Flame Ratings
The F-rating is expressed in hours and the number indicates the specific length of time that a barrier can withstand fire before being consumed or before permitting the passage of flame through the opening.
A F-rated opening shall also withstand a hose stream test.
T-rating, Thermal Ratings
The T-rating is expressed in hours and the number indicates the length of time that the temperature on the non-fire side of the penetration does not exceed 325 oF (163 oC) above the ambient temperature. This ensures that 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.
L-rating, Smoke Ratings
The L-rating is the amount of air (or cold smoke) that can leak through a penetration and the number indicates the amount of air in cubic feet per minute.
L-rating is tested under a differential pressure of 0.30 inches water column (75 Pa) at 75 oF and at 400 oF.
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