The present subject matter provides an oven appliance with a fluid analysis assembly fluidly mounted to a duct. The fluid analysis assembly includes a casing and a sensor array. A fluid inlet of the casing extends between the duct and a dilution chamber of the casing. An ambient inlet of the casing is contiguous with ambient air about the casing and the dilution chamber. The sensor array includes a plurality of fluid sensors positioned at the dilution chamber of the casing.