To determine whether the air quality inside armored-vehicle cabins can meet exposure guidelines under deployment conditions, the Army assessed possible synergistic toxic effects from potentially harmful substances. This book, the final of two reports on the subject from the National Research Council, addresses whether the approach discussed in the technical context section of the Army's proposed guidance is appropriate, or whether an alternative assessment method should be developed. Combined Exposures to Hydrogen Cyanide and Carbon Monoxide in Army Operations provides several conclusions and recommendations, including the use of alternative instrumentation for monitoring gas, conducting experiments on human subjects, and seeking advice from additional groups involved with personnel training and field deployment.