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Burning rate quantifies fire risks, guiding material selection and safety design across industries.

1. Definition: Dual Dimensions of Burning Rate

As a core parameter in fire science and material flammability assessment, burning rate quantifies the speed of combustion reactions or material ablation. It is expressed in two ways:

Chemical Reaction Rate: Measures consumption of reactants (mol/(L·s)) or product generation (kg/(m³·s)) via chemical kinetics.

Flame Spread Rate: Engineering metrics include flame front velocity (mm/s/m/s), mass loss rate (g/s), and linear ablation rate (mm/min).

2. Safety Impact: Fire Evolution Predictor

Burning rate directly determines fire scale and hazard:

High Rates (>50mm/s): Accelerate flame spread by 60%+, triple heat release rates (HRR), and reach toxic gas thresholds in 90s (e.g., polyurethane foam in building fires).

Low Rates (<10mm/s): Reduce fire size by 70%+. Aluminum hydroxide-filled epoxy composites lower mass loss rates by 82%, extending evacuation time to 8+ minutes.

3. Influencing Factors: Multidimensional Interactions

Three categories dynamically affect burning rates:

Material Properties:

Halogenated polymers (Cl/Br) reduce rates by 40–60% vs. hydrocarbons.

Thermal conductivity >0.5W/(m·K) correlates with slower combustion.

Nanoscale LDH additives cut polypropylene rates by 65%.

Environmental Conditions:

Oxygen reduction from 21% to 15% exponentially decreases wood combustion rates.

Forced convection at 3m/s doubles plastic burning rates.

Geometric Effects:

10mm-thick panels burn 38% slower than 5mm ones.

Vertical burning rates exceed horizontal ones by 1.8–2.5×.

4. Testing Standards: Quantitative Assessment Frameworks

Three-tier evaluation systems exist:

Basic Flammability Grading:

UL 94 tests classify materials (V-0 to HB) via afterflame time (<30s) and burn length (<25mm), covering 92% of electronics.

Limiting Oxygen Index (LOI):

Determines minimum oxygen concentration for sustained combustion. Materials with LOI>26% resist airborne ignition.

Fire Dynamics Simulation:

Cone calorimeters (CONE) measure 12 parameters under 10–100kW/m² heat flux. HRR peaks correlate strongly with burning rates (R²=0.97).

5. Industrial Applications: Safety Design Benchmarks

Aerospace: Phenolic composites with <0.8mm/min vertical burning rates pass 120s hypersonic heating tests.

Rail Transport: EN45545 mandates <100mm/min seat fabric rates, reduced by 45% with fire-retardant coatings.

Conclusion: As a quantitative bridge between material properties and fire behavior, precise burning rate control underpins modern fire safety systems, driving advancements from nanoscale flame retardants to large-scale fire experiments.