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Externally venting flames (EVF) may emerge through openings in fully developed under-ventilated compartment fires, significantly increasing the risk of fire spreading to higher floors or adjacent buildings. Several fire engineering correlations have been developed, aiming to describe the main characteristics of EVF that affect the fire safety design aspects of a building, such as EVF geometry, EVF centreline temperature and EVF-induced heat flux to the fac¸ade elements. This work is motivated by recent literature reports suggesting that existing correlations, proposed in fire safety design guidelines (e.g. Eurocodes), cannot describe with sufficient accuracy the characteristics of EVF under realistic fire conditions. In this context, a wide range of EVF correlations are comparatively assessed and evaluated. Quantification of their predictive capabilities is achieved by means of comparison with measurements obtained in 30 different large-scale compartment-fac¸ade fire experiments, covering a broad range of heat release rates (2.8 MW to 10.3 MW), ventilation factor values (2.6 m 5/2 to 11.53 m 5/2 ) and ventilation conditions (no forced draught, forced draught). A detailed analysis of the obtained results and the respective errors corroborates the fact that many correlations significantly under-predict critical physical parameters, thus resulting in reduced (non-conservative) fire safety levels. The effect of commonly used assumptions (e.g. EVF envelope shape or model parameters for convective and radiative heat transfer calculations) on the accuracy of the predicted values is determined, aiming to highlight the potential to improve the fire engineering design correlations currently available.Total area of vertical openings on all walls of the compartment c (4.67)Empirical factor (Eq. 19) C p (1005 J/kg K) Specific heat of air at ambient conditions D v (m)Effective diameter of the opening d eq (m)Characteristic length scale of an external structural element E b (kW/m 2 ) Black body emissive power g (9.81 m/s 2 )Gravitational acceleration H 0 (m)Opening height H u (13,100 kJ/kg O 2 )Heat release of cellulosic fuels for each kilogram of oxygen consumed h eq (m)Weighted average of openings heights on all walls k (m -1 ) Extinction coefficient k fuel (m -1 ) Extinction coefficient for the combustion products of a specific fuel L L_0.05 (m) Flame height at the ''continuous flame'' (5% flame intermittency limit) L L_0.50 (m) Flame height at the ''intermittent flame'' (50% flame intermittency limit) L L_0.95 (m) Flame height at the ''far-field flame'' (95% flame intermittency limit) L L (m) Height of EVF L H (m) Projection of EVF L f (m) Flame length l (-) Characteristic length scale (Eq. 9) l x (m) Length along the EVF centerline, originating at the opening _ m a (kg/s) Air mass flow rate (entering the fire compartment) _ m f (kg/s) Fuel mass flow rate _ m O2 (kg/s) Oxygen mass flow rate _ m g (kg) Mass flow rate of unburnt gases venting outside the fire compartment _ Q (MW) Heat Release Rate _ Q ex (MW) Excess Heat Rele...

In a compartment fire, Externally Venting Flames (EVF) may significantly increase the risk of fire spreading to adjacent floors or buildings; EVF-induced risks are constantly growing due to the ever-increasing trend of using combustible materials in building facades. The main aim of this work is to investigate the fundamental physical phenomena associated with Externally Venting Flames (EVF) and the factors influencing their dynamic development. In this context, a series of fire tests is conducted in a medium-scale compartment-façade configuration; an n-hexane liquid pool fire is employed, aiming to realistically simulate an "expendable" fire source. A parametric study is performed by varying the fire load density (127.75, 255.5 and 511 MJ/m 2) and opening factor (0.071 and 0.033 m 3/2). Emphasis is given to characterization of the thermal field developing adjacent to the façade wall. Experimental results suggest that the three characteristic EVF phases, namely "internal flaming", "intermittent flame ejection" and "consistent external flaming", are mainly affected by the opening dimensions, whereas the fuel load has a notable impact on the fuel consumption rate and heat flux to the façade. Fuel consumption rates were found to increase with increasing fire load and opening area, whereas the global equivalence ratio increases with decreasing opening factor. The obtained extensive set of experimental data can be used to validate CFD fire models as well as to evaluate the accuracy of available fire design correlations.

A full-scale compartment fire test was performed to assess gypsum plasterboards and wood based panels as cladding materials for the fire protection of light and massive timber elements.The test compartment was constructed using both the Timber Frame and the Cross Laminated Timber techniques; a wood crib was used to achieve realistic fire conditions. Temperature measurements and optical inspection evidence suggested that gypsum plasterboards offered adequate fire protection since they did not fail and no charring was observed in the timber elements. A free standing wall inside the test compartment, protected by wood-based panels, partially collapsed. Measured values of characteristic failure times, such as time to failure of fire protection cladding and time to onset of charring, were compared to relevant Eurocode correlations, achieving good levels of agreement. The obtained set of measurements, describing the time evolution of a large variety of physical parameters, such as gas and wall layer temperatures, can be used for validation of relevant advanced fire simulation tools.

In a compartment fire, Externally Venting Flames (EVF) may significantly increase the risk of fire spreading to adjacent floors or buildings, especially when combustible insulation materials are installed on the building façade. An increasing number of recent reports suggest that existing fire engineering design methodologies cannot describe with sufficient accuracy the characteristics of EVF under realistic fire load conditions. In this context, a series of fire safety engineering design correlations used to describe the main EVF thermal characteristics, namely EVF centreline temperature and EVF-induced heat flux on the exposed façade surface, are comparatively assessed. Towards this end, measurements obtained in a medium-and a large-scale compartment-façade fire test are employed; aiming to broaden the scope of the validation study, predictions of the investigated correlations are further compared to measurements obtained in 6 large-scale fire tests found in the literature. It is found that the correlation proposed in EN1991-1-2 (Eurocode 1) for the estimation of the EVF centreline temperature is under-predicting the measured values in large-scale fire tests. In addition, it is concluded that estimation of the local flame emissivity should take into account the specific fuel type used in each case.