Abstract: A ceramic diffuser assembly containing a diffuser fitting integrally connected to a diffuser body, Wwhen the ceramic diffuser assembly is supplied with oxygen-containing gas at a pressure of from about 0.2 to about 80 pounds per square inch, the gas flows through it at a rate of from about 0.5 to about 50 standard cubic feet per minute, the plot of gas pressure versus flow rate is a straight line, and the slope of said straight line is from about 0.1 to about 4. The diffuser body contains a first ceramic layer, a second ceramic layer, and a recessed area disposed between the first and second layers.