A channel letter has a rear surface for mounting against a raceway, wall, or a structure for supporting the signage, and sheet metal sides defining the figuration of the letter or shape to be depicted. A client hashes keywords related to files using a symmetric key algorithm, and encodes the hashed keywords. The ceramic body has a slot therein into which the plastic inlet is fitted. The absolute humidity of the air of the primary air stream is at least equal to that of the cold secondary air stream and lower than that of the warm secondary air stream.