Soldiers wearing Mission-Oriented Protective Posture (MOPP) gear must drink more water than usual to prevent heat stress. But for soldiers equipped with a protective mask (gasmask), the use of a water canteen becomes problematic. In order to drink, the mask must be removed, an action that risks exposure to toxic substances. The solution to this problem is a drinking tube that connects a straw inside the mask to the canteen through a special canteen cap.
COL Charles Dunn, 43rd Mission Support Group Commander, 43rd Airlift Wing, tests a canteen drinking tube, Pope AFB, 4 Sep 2008.
During NBC attacks (Nuclear-Biological-Chemical warfare), it's possible for the soldier to drink without removing his mask or exposing the contents of the canteen to contamination. But before connecting and drinking via the M-1 cap and gasmask drinking tube, the soldier must verify by using M8 Chemical Detection Paper (or other appropriate detection method) that the canteen and exterior coupling are not contaminated.
When drinking from a canteen via a gasmask drinking tube, the soldier holds his canteen vertically with the cap down. Water may then be drawn through the tube, until air pressure needs to be equalized. The soldier blows air through the drinking tube to restore pressure to the canteen, then can resume drinking until the procedure needs to be repeated. In this way, the exchange of water in the canteen for air is accomplished without any chance of contamination.
The process described permits the MOPP user to drink while in a contaminated environment, but water intake is somewhat restricted. This may lead to dehydration, especially during prolonged wearing of the MOPP4 configuration in hot weather. Drinking before anticipated MOPP conditions should be enforced through the use of command directed drinking.
When the Flexible Canteen is used (one or two quart canteen made of softer, flexible plastic) it is easier to drink while wearing a protective mask. The canteen can be squeezed to increase pressure and reduce the effort of equalizing air pressure.
To be compatible with the mask drinking tubes, the cap of the M1961 canteen was modified by the addition of a small connecting hole in the center of the cap. The cap contains a pin that depresses a diaphragm on the end of the drinking tube, allowing the wearer to replenish fluids while wearing the mask. A small fliptop cover is attached to the cap that snaps into place to expose or hide the connecting point.
The new cap is known as the NBC canteen cap. It is identified by NSN 8465-00-930-2077 and specification MIL-C-51278D, with nomenclature Cap, Water, Canteen. It is also called the M-1 canteen cap. The same cap fits one and two quart plastic canteens, and, with a retrofit kit, the Arctic Canteen (see below).
New military canteens already have the NBC cap installed, but older model canteens must have the cap replaced. The NBC canteen cap for one and two quart plastic canteens can be ordered from Amazon.com at the link above or through military channels by using the NSN given above. The NSN information for all the canteen components is also on the Military Plastic Canteen page.
A different kit was provided to retrofit the Arctic Canteen: Adapter Kit, M-1 Cap; for Canteen, Water, Insulated identified by NSN 8465-01-278-3739 described by specification MIL-A-44264. This kit replaces the whole mouthpiece section of the Arctic Canteen with a new neck. Once the new neck is installed, the NBC cap and its attachment strap fit right on. Everything needed for the replacement is included in the kit.
Find More Information on the Internet
There are many fine websites that have additional information on this
topic, too many to list here and too many to keep up with as they come and go.
Use this Google web search form to get an up to date report of what's out there.
For good results, try entering this: m1 nbc canteen cap. Then click the Search button.