Yes - our protective masks can be used without filters. The mask has two layers of 100% cotton so even without the filters, the masks by themselves are in line with the CDC recommendation of wearing face coverings. The filters add significantly higher protection, with two layers of meltblown polypropylene, however the masks can be worn without the filters.
Our Sustainable KN95 masks actually have the filter built into the mask. It consists of 5 layers of a lab-tested filtration system, which is made of 50% hot air cotton, 30% non-woven polypropylene, and 20% meltblown propylene.