My son the oral surgeon re-used masks in the early days and did not have a problem. Our anesthesiologists use the re-useable envo. I do too. Have also double masked with KN95 with simple surgical mask over it, flown since last October, exposed to COVID patients at work, and as of last week have not have COVID but do have antibodies to the spike >2500, thank you Pfizer. I also got some lanyards that tighten up the outer mask, which is better than loose, and allow it to come off for food, stay off the ears, etc then go back on. As for double masking the IOM supported it in 2006 but the CDC and WHO apparently ignored this information. Our family double masks on a plane. Single mask with distancing in the airport.
In a study conducted in 2006, the Institute of Medicine (IOM) evaluated the potential for reuse of N95® in the case of an influenza pandemic. The IOM stated that the simultaneous use of an N95® and a surgical mask as an external barrier, or a washable face shield, could extend the duration of its usefulness, acting as a physical barrier to potentially infectious fluids and a block of larger particles.[1] They also discovered that the use of a single cloth or surgical mask blocked only ∼42–44% of the particles of a simulated cough. However, when a cloth mask was worn over a surgical mask, 92.5% of the cough particles were blocked.[1]
https://envomask.com/
https://www.thieme-connect.com/produ...s-0041-1728716
Institute of Medicine. 2006. Reusability of Facemasks During an Influenza Pandemic: Facing the Flu. Washington, DC: The National Academies Press. https://doi.org/10.17226/11637.
lanyard