*How Stuff Works - Gas Masks*Your Gas mask Guide to the maintenance of your gas mask*Respirator Fact Sheet*CBRN SCBA NIOSH Approved Respirators List of NIOSH Approved CBRN SCBA respirators* World War 1 gas mask technology - "Combating Man's Deadliest Peril: How the unending struggle between gas and mask is carried on", Popular Science monthly, December 1918, page 64, Scanned by Google Books: http://books.google.com/books?id=EikDAAAAMBAJ&pg=PA64*{http://search.ebscohost.com.lib-proxy.fullerton.edu/login.aspx%3fdirect%3dtrue%26db%3dant%26AN%3dXANL668213267%26site%3dehost-live%26scope%3dsite}===Links to images===*WWII gasmasks with hose and canister*Modern gas mask with one big front window
* Gas Masks UK Information on gas masks from many countries.