Airworthiness Directives; Boeing Model 737-300, -400, and -500 Series Airplanes

We are adopting a new airworthiness directive (AD) for certain Boeing Model 737-300, -400, and -500 series airplanes. This AD requires an inspection to determine the manufacturer and manufacture date of the oxygen masks in the passenger service unit and the lavatory and attendant box assemblies, corrective action if necessary, and other specified action. This AD results from a report that several passenger masks with broken in-line flow indicators were found following a mask deployment. We are issuing this AD to prevent the in-line flow indicators of the passenger oxygen masks from fracturing and separating, which could inhibit oxygen flow to the masks and consequently result in exposure of the passengers and cabin attendants to hypoxia following a depressurization event.