Filter media for filtering gas streams (e.g., air) are described herein. In some embodiments, the filter media may be designed to have desirable properties such as stable filtration efficiency, high oil repellency, low instantaneous resistance, and/or stable service life. In certain embodiments, one or more layers of the media may have a certain value of basis weight over air permeability (and/or a ratio of a value of basis weight over air permeability between two layers). The filter media may optionally comprise a support layer with a relatively high air permeability (e.g., greater than or equal to 1100 CFM). In some cases, the filter media may have a relatively low initial resistance and/or may have a particular final El efficiency. The filter media described herein may be particularly well-suited for applications that involve filtering gas streams (e.g., face masks, cabin air filtration, vacuum filtration, respirator equipment, as well as residential heating ventilation and air conditioning (HVAC) and industrial HVAC systems), though the media may also be used in other applications.