> The most important distinction between mask models is that some models have valves / vents and some do not. The most important distinctions also include: 1)

> The most important distinction between mask models is that some models have valves / vents and some do not. The most important distinctions also include: 1) Fit. This matters a lot. 2) Nano versus electrostatic technology. 3) Filtration level. "N95" advertised isn't always 95% in reality, and some are 99+%. 4) Impedance to airflow #4 is more than just comfort it determines how much air goes around the mask.