Abstract: In one embodiment, a removable air filter is mounted proximate to where electrical equipment is mounted in a case. The filter has at least two sections with different finite air impedances. The filter is constructed of a filter media mounted inside of a frame. When the equipment arrangement is modified, the filter can be replaced with another filter with a different impedance profile, such that the air flow remains optimal for many equipment arrangements. The impedance profile can also be tailored to compensate for the characteristic airflow of the case design. Other embodiments are described and claimed.