A water separator for use in an environmental control system includes an insert having an open first end, a closed second end, and at least one sidewall extending between the first end and the second end such that a hollow interior is defined between the first end, the second end, and the at least one sidewall. The at least one sidewall includes at least one flow passage such that a flow of medium is configured to flow radially from the interior of the insert through the at least one sidewall.

An air filter comprises: a first filter frame in which a plurality of first chambers are formed; a second filter frame in which a plurality of second chambers are formed and which is arranged at the rear of the first filter frame; and a filter material which is accommodated in the plurality of first chambers and the plurality of second chambers to filter air, wherein the first filter frame and the second filter frame are arranged so that, when seen from the front, the center of each of the plurality of second chambers is out of line with the center of each of the plurality of first chambers, in the vertical direction.

A fresh air ventilation device for air pollution prevention includes a main body, a blower, a filtering and cleaning assembly, and a gas detection module. The blower is disposed in the main body to guide air convection and form a flow-guiding path. The filtering and cleaning assembly is disposed in the flow-guiding path to filter and clean an air pollution source in the air convection guided by the blower. The gas detection module is disposed in the flow-guiding path of the main body to detect the air pollution source and transmit a gas detection data.