Overall, technically you can use fusible interfacing in face masks. It will provide some filtration (to block out particles) and it's breathable.

What interfacing should I use for a face mask?

Any non-woven interfacing is suitable for use in a face mask. Woven interfacing is not better for filtration than any other regular fabric because a woven material inherently has gaps between the fibers which are quite large, comparable with the thread size.

Is fusible interfacing toxic for masks?

Is fusible interfacing safe to breathe? Fusible webbing is just a thin layer of iron activated adhesive that makes the stitching job easier by holding it in place. It will wash out and is not harmful.