The ornamental design for a multi-functional air quality control system, as shown and described.
FIG. 1 is a front perspective view of a multi-functional air quality control system in accordance with the present invention;
FIG. 2 is a front elevational view thereof;
FIG. 3 is a back elevational view thereof;
FIG. 4 is a top plan view thereof, the bottom plan view being a mirror image;
FIG. 5 is a left side elevational view thereof; the right side elevational view being a mirror thereof; and,
FIG. 6 is a front perspective view of the multi-functional air quality control system shown mounted in a window to illustrate an operating environment thereof in accordance with the present invention.
The broken lines in the drawings illustrate portions of the window air conditioner which form no part of the claimed design.