This is off-topic, but important. It turns out that cheap, throw-away "surgical mask, 3-layer" type masks work best. These are the ones you can buy anywhere nowadays. Office Depot sells them cheap.
See this research article in Science: https://advances.sciencemag.org/content/early/2020/08/07/sciadv.abd3083 Knitted and bandana types are not recommended. >
