“Facemasks” is disposable masks cleared by the U.S. FDA for using as medical devices. A 
respirator is a device designed to protect the wearer from inhaling harmful dusts, fumes, vapors, gases and/or very small particles, which might contain viruses (source: wikipedia.org). Facemasks and/or respirators may help to prevent some exposures while in a crowded setting.
As stated in its original site, this article tended as an interim guidance for the use of facemasks and respirators due to controlling influenza pandemic, for it will be updated as new information becomes available. In the following article, we can find descriptions about the use of facemasks and respirators in non-Occupational Community Settings such as schools, public gatherings, and households.
There are descriptions of recommendation in avoiding the source, when individuals are containing the source, prevent/limit the exposure, length of time and risks of exposure, and considerations aspect in using facemasks and respirators. Also descriptions of appendix that summarizes the interim guidance for facemask and respirator use during a pandemic and section which described: what you should know about using facemasks and respirators that contained taking protective actions, and the benefits of wearing a facemask or a respirator during a flu pandemic.
It is noted that neither a facemask nor a respirator will give complete protection from the flu, they should be used in combination with other preventive measures, such as hand hygiene and social distancing, to help reduce the risk for influenza infection during a pandemic, accordingly.
Complete your informations of Facemasks or Respirators in Controlling Pandemic Influenza in 13 pages/116 Kb in pdf format (source: pandemicflu.gov, image: qandil.co.uk)
