Description Features Reviews VENT Performance Filters are 99% particulate certified giving you piece of mind while you train in high smog, high allergen, and high dust environments. You can breathe in up to 7 times more air when you are working out than you do at rest putting your lung health in jeopardy if you don't live in a clean air environment outside of cities, urban areas, and high pollen zones. VENT filters are very easy to change and click quickly into place beneath the filter trap cage underneath the main front cap of your Training Mask VENT. Please Note: VENT trap cage is designed for one filter only. Putting more than one filter in the trap cage may reduce mask performance.