Masks with valves are only designed to limit particle flow inwards, otherwise the valves area would have to have the same thickness and construction as the rest

Masks with valves are only designed to limit particle flow inwards, otherwise the valves area would have to have the same thickness and construction as the rest of the mask. The mask is not just about stopping you getting infected by something, it’s also about reducing your ability to transmit it to others. In fact a mask is more effective at limit transmission from you than to you. That’s why we have multiple layers - everyone wears a mask, limits travel, limits exposure to others, ensures as much distance as possible, maximizes the surrounding air volume when in the presence of others, etc.