I see a potential problem with this adapter, other than the disclaimer of the filters (not provided, by he way, as this is simply an adapter).
Most half-face and full-face respirators have separate routes for inhalation and exhalation. You inhale through the filter, and exhale through an exhalation valve in a separate location. The filter is protected from exhalations by a non-return mushroom valve. That way, the filter does not have to cope with water vapor affecting the filter.
But with this adapter, the exhalation goes back through the filter, backwards. The filter is subjected to water vapor, which can the condense on the filter, soaking the filter with water. I don't think this is a good idea. If the filter is a HEPA filter (high efficiency particulate air filter) being soaked in water can inhibit its efficiency, and make for hard breathing. If it includes a organic vapor cartridge, which has activated carbon, the water vapor could cause the filter to loose its ability to absorb organic vapors.
One further cause for concern is that this system is not tested by NIOSH (the National Institute for Occupational Safety and Health), and has not received a technical certification number ("TC Number) from them. It therefore cannot legally be used as Personal Protective Equipment (PPE). Although these rules have been loosened because of shortages of PPE, I would not rely upon this adapter to frunction as PPE for me or my loved ones.
SeaRat
John C. Ratliff, CSP(retired), CIH(2006-2018), MSPH