A biofiltration apparatus and method for reducing methyl bromide concentration in a volume of a gas are disclosed. The apparatus includes a housing and a substrate component located in the housing. The substrate component includes a population of methyl bromide degrading microorganisms. The housing receives a volume of contaminated gas, such as exhaust from a fumigation site, through a contaminated gas inlet. The contaminated gas is exposed to the methyl bromide degrading microorganisms where the methyl bromide is biodegraded. The filtered gas, or the gas with a reduced methyl bromide concentration, is then directed out of the housing. The apparatus may also include a contaminated gas load dampening device.