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Gas Masks

Dateline: 10/26/98

By Alan Bruzel

Defense against inhalation of toxic substances requires thoughtful identification of those hazards present in one's immediate surroundings. The atmosphere is 21% oxygen, with the remainder nitrogen (78%) and argon (1%). In conditions where the oxygen concentration falls to 16% or less, one does not reach for an air-purifying device; it makes little sense to purify oxygen-deficient air. In these circumstances, survival demands a self-contained breathing apparatus carrying its own air supply.

In situations where the oxygen concentration supports respiration, but the air contains dusts or mists, a particulate respirator is used. Here, a filter removes the offending particles before they can be inhaled. To remove noxious gases and chemical fumes (when present at low levels!), a chemical cartridge respirator is recommended. The heart of this device is a cartridge or canister containing an adsorbent such as activated carbon, which removes many organic and inorganic compounds, even if they are present at low concentrations. The chemical cartridge respirator may provide protection for as little as ten minutes or for up to eight hours, depending upon the substance present and its concentration.

A gas mask is an augmented chemical cartridge respirator consisting of a dust filter, a full facemask covering mouth, nose, and eyes (microphone and laser ballistic eye protection in some models), and a reservoir with a larger quantity of adsorbent. This reservoir is generally connected to the facemask with a flexible hose. Unfortunately, chemical agents may enter the body other than through the lungs. Because nerve gases, for example, penetrate the skin, an activated carbon inner layer allows the wearer of the US Army's Chemical Protective Suit a reasonable measure of protection when worn with an appropriate gas mask.

Recommended Web resources for additional information:

Activated Carbon Hall of Fame
Brief biography of Jonathan C. Cooper, developer of activated carbon gas mask. From Carbon News Online.

Chemical and Biological Warfare: Are the United States Navy and Marine Corps Prepared?
Article by Nicholas S. Chekan for the Federation of American Scientists. Describes US military gas masks including the Navy's MCU-2P and the M40A1 used by the Army and Marine Corps.

Frequently Asked Questions about Gas Masks
Presented by Gas Masks, Inc.

How to Protect Yourself from Respiratory Hazards
Information for farm workers from David E. Baker, Brooke Ballenger, and Rusty Lee, University of Missouri at Columbia.

Morgan, Garrett Augustus
Some specifications for a breathing device used in fire rescue. From The Faces of Science: African Americans in the Sciences.

Nobel Prize in Chemistry 1948
Speech by A. Westgren relating gas mask adsorption phenomena to Arne Tiselius's Nobel prize-winning work on analysis by adsorption.

Personal Protective Equipment
Information provided includes respiratory protection factsheet. From Pennsylvania State University.

Respirator Selection
Information on the different types of respirators and when they should be used. From the Canadian Centre for Occupational Health and Safety.

Respirator Specifics: Selection, Types, and Use
Information about many types of respirators. From Lab Safety Supply Inc.

Storing Natural Gas
Methane may be stored at low pressures by adsorption to carbon atoms, thereby avoiding problems associated with high-pressure cylinder storage.

What Happens to Gas in a Gas Mask?
Answered by Louis A. Bloomfield, University of Virginia.

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