This is the forth half of the post on air. You will find links to other bloggers and websites about the subject for this week.
Blogs:
I couldn't find any blog posts about air. Bummer
Websites:
Global Security - M40/M42 Series Chemical-Biological Mask
http://www.globalsecurity.org/military/systems/ground/m40m42.htm
Defense Technical Information Center - History of the Army Protective Mask
http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA376445&Location=U2&doc=GetTRDoc.pdf
Unknown - Who Invented the Gas Mask?
http://www33.brinkster.com/iiiii/gasmask/page.html