Otitis media secretions from the nasopharynx into the normally sterile middle-ear space, the fluid may then become infected — usually with bacteria. The virus that caused the initial URI (upper respiratory infection) can itself be identified as the pathogen causing the infection. As its typical symptoms overlap with other conditions, such as acute external otitis, clinical history alone is not sufficient to predict whether acute otitis media is present; it has to be complemented by visualization of the tympanic membrane. Examiners use a pneumatic otoscope with a rubber bulb attached to assess the mobility of the tympanic membrane. In more severe cases,
Membrane technology utilized for gas separations (removal of CO from natural gas, separating N from air, organic vapor removal from air or a nitrogen stream) and sometimes in membrane distillation. The later process helps in the separation of azeotropic compositions reducing the costs of distillation processes. The pore sizes of technical membranes are specified differently depending on the manufacturer. One common distinction is by "nominal pore size". It describes the maximum pore size distribution and gives only vague information about the retention capacity of a membrane. The exclusion limit or "cut-off" of the membrane is usually specified in the form of "NMWC"