Method of removing contaminants from an aerosol using a new electret article

A method of filtering contaminants, which method comprises:

• passing an aerosol through a nonwoven fibrous web electret that comprises polymeric microfibers, the nonwoven web having a surface fluorination that comprises CF3 and CF2 at a CF3:CF2 ratio of at least 0.45 as determined according to the Method for Determining CF3:CF2, and wherein:
• the electret exhibits a quality factor QF of at least about 0.25/mm H2O;
• the microfibers are melt-blown microfibers that have an effective fiber diameter of 1 to 50 micrometers, the melt-blown microfibers comprising a polypropylene resin that has a resistivity greater than 1014 ohm-cm;
• and
• the nonwoven web has a basis weight of 10 to 100 g/m2 and has a thickness of 0.25 to 20 mm;
• the aerosol being passed through the nonwoven fibrous electret to remove contaminants therefrom.