Abstract: A gas generator to produce formaldehyde gas in enclosed spaces such as animal houses or for conveying such gas to inaccessible areas through a flexible hose which includes a base and hood mounted thereon. The base is in the form of an open topped container having a heating element oriented under the bottom wall thereof and in heat exchange relation to water and paraformaldehyde flakes or formalgen powder in shallow compartments interiorly of the container for producing formaldehyde gas and water vapor that is heated above ambient temperature. The container includes air inlet slots adjacent to but below the open top and below the lower edge of the hood which is supported on supporting ledge structures on the interior of the container whereby air is entrained into the upwardly moving gas and water vapor for mixing therewith and assisting in disseminating the gas into all areas of the enclosed space when the gas, moisture and air mixture is discharged from an opening in the upper end of the hood.