Abstract: In a sealed cabin of the manned spacecraft, the nonmetallic materials in the pyrotechnic ignition process may lead to a rise of the carbon monoxide density inside the chamber, as a hazardous situation for the crew. Based on the analysis of the origin of the carbon monoxide, many countermeasures are proposed, such as the control of the nonmetallic materials, the limiting of the leakage rate, and the adequate ventilation and purification. The above measures are tested for their effectiveness, and they may be used for the subsequent engineering design.