Which of the following is NOT a result of environmental control system failure?

Effective oxygen retention is not a result of environmental control system failure because the environmental control system's primary functions are to regulate cabin temperature, pressure, and air quality. When this system fails, it typically leads to conditions such as increased cabin temperature, uncomfortable cockpit conditions, and a potential risk to crew and passengers due to inadequate breathing air or temperature extremes. However, effective oxygen retention would imply that the oxygen levels and quality in the cabin remain sufficient despite the failure of other environmental controls. In cases of a failure, often the opposite occurs, where oxygen levels may not be effectively maintained, leading to potential hypoxia or other issues. Thus, while the other options pertain directly to the consequences of an environmental control system malfunction, effective oxygen retention does not.