In a display apparatus having a backlight unit, a light unit includes plural light source strings commonly connected to an output terminal of a boosting circuit to generate light in response to a light source driving voltage. The valve assembly controls the directional flow of an influent gas mixture into one of two vertical desiccant tanks of an adsorbent fractionator, or desiccant dryer, and an effluent gas flowing in reverse through the opposite desiccant tank. A reed retaining body is formed on the mouthpiece body for removably securing a reed to the mouthpiece includes first and second upstanding walls and a transverse portion extending therebetween.