I remodeled the 3DP mask to have an exhaust vent. This should improve overall breathability and reduce wearer irritation while maintaining mask integrity. The o-ring is a master car product (9262K622) but plumbing o-ring with 25mm OD will also work. Rubber weather stripping or .25" adhesive foam can be used to seal the mask to the wearer (note: foam  is less than ideal due to sanitation limitations, if foam is being used ensure that it is replaceable at the end of every shift)