The effectiveness of respiratory protection worn by communities to protect from volcanic ash inhalation. Part I: Filtration efficiency tests - ScienceDirect

The above is a detailed scientific study on which types of masks should be used. Regular surgical masks, scooter/biker masks, and other cloth masks fared poorly against particulate matter coming from volcanic ash.

"Overall, four RP materials performed very well against volcanic ash, with median FEs in excess of 98% (N95-equiv., N99-equiv., PM2.5 surgical (Japan), and Basic flat-fold (Indonesia))."

"This evidence base indicates that materials used in industry-certified masks, and others, specifically designed to filter PM2.5 particles, will provide better filtration efficiencies than fashion/scooter masks or ad hoc cloth materials (e.g., bandanas, scarves) used for protection when ash is in the air. Pleated, standard, surgical masks also had good filtration efficiencies, but other types of masks (non-pleated, single layer) for use in healthcare settings performed very poorly against volcanic ash. "