Plasma Display Panel is a display device emitting fluorescent light from gas discharge between a front and a rear panel sealed together. Front and rear panel have multitude of film layers and barrier ribs in the rear panel has the largest area so releasing various gases and affecting light emitting characteristics and lifetime. The remaining gases in a barrier rib were studied by thermal desorption analysis up to $400^{circ}C$ and main gases were $H_2$ $H_2$O, CO. During sustaining at $300^{circ}C$, the outgassing rates from other gases were decreased but$ H_2$ kept constantly increasing until 1 hour, which can be originated from the dissociation of organics remained in the inside of barrier rib material. In $H_2$O, two distinct peaks were observed: desorption from physically adsorbed one at $l00^{circ}C$ and from chemically adsorbed one $400^{circ}C$. The result can be utilized in interpretation of electronic and optical characteristics and evacuation process control of PDP