Impregnation apparatus and method

Apparel us for impregnating a porous substrate (e.g., wood) with an active agent, including a reservoir for containing a low boiling fluid, a controllable first fluid pathway to permit fluid to flow from the reservoir to a treatment vessel, a fluid junction for introducing the active agent into the first fluid pathway to permit mixing of the active agent with the low boiling fluid to produce an impregnation fluid containing an initial level of active agent and a controllable second fluid pathway to allow fluid to flow from the treatment vessel to the reservoir. The treatment vessel contains the porous substrate while it contacts the impregnation fluid in a liquid state to produce a treated substrate impregnated with the active agent. Also, a method for impregnating a substrate with an active agent, including preparing an impregnation fluid including a low boiling solvent and an active agent, and optionally a co-solvent, contacting the porous substrate with the impregnation fluid in a liquid substrate in an impregnation chamber and removing the impregnation fluid.