Diffusion of Carbon Monoxide Through Unpainted and Painted Gypsum Wallboard

Abstract

Experiments were conducted to measure effective diffusion coefficients of carbon monoxide through unpainted and painted gypsum wallboard samples. The results show carbon monoxide readily diffusions through gypsum wallboard while application of paint to one surface was shown to have almost no effect, a few percent decreases in the effective diffusion coefficient, to a dramatic reduction in carbon monoxide diffusion, up to 55-fold decrease in the effective diffusion coefficient for samples with two coats of one house paint. All three paints examined were flat-finish, latex-based interior house paints; clearly, the paint chemical formulation affects gas permeability and hence the effective diffusion coefficient for painted surfaces. Two full-scale experiments were conducted in a 11.0 m by 7.3 m by 3.7 m high sealed compartment fabricated with one layer of either unpainted or painted gypsum wallboard on the walls and ceiling. In each experiment, carbon monoxide was released in the compartment, and after the release, the decay of the carbon monoxide concentration was recorded. Over a five-hour period, the painted walls and ceiling experiment’s carbon monoxide concentration slightly lagged the unpainted walls and ceiling experiment’s measurements which is consistent with the effective diffusion coefficient measurements of the unpainted and painted wallboard samples. The implications for life safety assessment compel one to conservatively assume carbon monoxide diffusion through gypsum wallboard progresses at the higher rate commensurate with an unpainted surface unless specific data is gathered. In full-scale fire experiments with conventional gypsum wallboard construction effects of carbon monoxide diffusion should be considered where carbon monoxide measurements are made.