Results of a recently completed National Institute for Occupational Safety and Health (NIOSH) study confirm the necessity of the current Occupational Safety and Health Administration (OSHA) respirator fit testing requirement, both annually and when physical changes have occurred. The study’s conclusions emphasize that respirator users who have lost more than 20 pounds should be re-tested to be sure that the current size and model of respirator in use still properly fits.

Read entire article - http://blogs.cdc.gov/niosh-science-blog/2016/01/05/fit-testing/