Firestop Rating

Overview

Engineering reference data for Firestop Rating in material science and properties.

Key Formulas

Stress

$\sigma = \frac{F}{A}$

Force per unit area.

Strain

$\varepsilon = \frac{\Delta L}{L_0}$

Change in length per original length.

Hooke's Law

$\sigma = E \varepsilon$

Stress proportional to strain in elastic region.

Thermal Expansion

$\Delta L = \alpha L_0 \Delta T$

Length change due to temperature.

Variables

Firestop Rating System

Firestop systems are categorized by their performance characteristics under standardized test conditions, primarily according to ASTM E814. The main ratings are:

F-Rating (Flame Rating)

The F-rating is expressed in hours and indicates the time a firestop system can withstand a standard fire exposure before:

1. Permitting the passage of flame through the opening, or
2. Being consumed (for combustible seals).

An F-rated assembly must also pass the hose stream test following the fire exposure, demonstrating resistance to the impact and erosion of a high-pressure water stream.

T-Rating (Thermal Rating)

The T-rating is expressed in hours and indicates the time until the temperature on the non-fire side of the penetration rises by a specified amount. The criterion is:

$T_{non-fire} \leq T_{ambient} + 325°F \ (163°C)$

Where:

• $T_{non-fire}$ is the temperature on the unexposed side of the assembly.
• $T_{ambient}$ is the initial ambient temperature.

This rating ensures materials on the "safe" side of the barrier do not reach their auto-ignition temperature due to conducted heat.

L-Rating (Smoke Rating)

The L-rating quantifies air or cold smoke leakage through the penetration and is expressed in cubic feet per minute (cfm) at a specific pressure. Testing is conducted under two conditions:

1. At 75°F (24°C) ambient temperature.
2. At 400°F (204°C) ambient temperature.

The standard test differential pressure is 0.30 inches of water column, which is equivalent to: $0.30 \ in \ H_2O \approx 75 \ Pa$

References

• Original Source