@baz10 There are different ratings for surgical masks. If you are trying to stop dust and allergens, a good mask for this is the #1820 Procedure mask from 3M. It has greater than 99% bacterial filtration efficiency @ 0.1 micron particles and the box says it helps reduce exposure to blood and body fluids, and minimizes patient contamination to exhaled microorganisms. They are latex free and have ear loops instead of ties and are comfortable. I bought these because I have asthma and they help a lot since this is equivalent to a HEPA filter. They have masks just like this for surgeons with ties instead of ear loops. The ties would make it more snug on your face, but ear loops are easier and more comfortable. I bought them online from Walmart.