Chemical hood glass failure under thermal loading associated with fire

The laboratory chemical hood is the primary engineering control when using toxic and flammable chemicals in the laboratory. A sustained fire in a chemical hood can be large safety risk because of its potential to affect the chemical hood's containment integrity. Under certain conditions when the glass is exposed to thermal loading, the glass fails under a brittle fast facture. The details of the thermal loading on the glass are important to the overall stability of the glass. To better understand how fire in a compartment influences the thermal history and cracking of its glass windows, a computational and experimental study was undertaken. The gas and glass temperatures were modeled with the computational fluid dynamics code Fire Dynamics Simulator (FDS). Small-scale fires are simulated by adjusting the heat release rate to that used in the experiments. FDS models allow results from simulations on small-scale tests of window heating and deformation to be applied to a large-scale chemical hood fire. Collecting images throughout the experiment with the IR camera, showed similar trends in heating as the simulations. It was found that temperature gradients develop due to varying rates of heating between exposed and unexposed (protected by frame) glass. The correlation of simulation results with experimental data can be particularly useful in gaining insight into the underlying physics of the fire. Studies of this type can be helpful in identifying the mechanisms for glass failure and designing mitigating features to eliminate glass failure modes during a chemical hood fire. In this paper, simulation data to better understand the effects of fire on thermal loading and glass failure in a chemical hood are discussed.