Once worn by painters and carpenters, the simple breathing mask needs a little instruction to do it's job. Long time STEM advocate, Richard Williams (Corporal Willy) put together this document.  

Criss-cross straps provide a tight fight. Use chap-stick/ lip balm /Vaseline on your lips so they do not dry out.

This morning over coffee, David also reminded me that when he worked in the power plant, he could not have a beard for his respirator.  

You need a good seal - no matter what type of mask you are using in order to do it's job.