Sport Mask With Exhalation Valves Filters. We do not recommend wearing these indoors. The length of time the filter is actively working;
• soft, stretchy washable fabric. Usually one filter can be used for 30 days. Details about sport mask with exhalation valves, reusable with extra 2 filters + and 2 valves.
There are only 2 items left in stock.
• adjustable velcro back closure. The exhalation valve opens in response to increased pressure when the wearer exhales to allow the exhaled air to be rapidly purged from the mask interior. So an n95 mask comes in two flavors, with and without valves. They filtered particulate matter, aka dust, from the air that.