Which two gases are primarily toxic or lethal in smoke from burning composites?

The choice of carbon monoxide and hydrogen cyanide as the primarily toxic or lethal gases in smoke from burning composites is rooted in their characteristics and effects on human health.

Carbon monoxide is a colorless, odorless gas produced during incomplete combustion of carbon-containing materials, including many composites. It binds with hemoglobin in the blood more effectively than oxygen does, leading to reduced oxygen transport in the body. Even in small concentrations, it can cause symptoms like headaches, dizziness, and potentially fatal outcomes if exposure is prolonged or at high levels.

Hydrogen cyanide, on the other hand, is highly toxic and can result from the combustion of nitrogen-containing materials, which are often present in composite materials. It disrupts cellular respiration by inhibiting the body's ability to use oxygen, leading to rapid unconsciousness and death if inhaled in significant quantities.

Together, these gases represent a significant hazard in fire scenarios involving composite materials, underscoring the importance of understanding the risks associated with smoke inhalation in such events. The other options provided involve gases that do not have the same acute toxicity or lethal potential as carbon monoxide and hydrogen cyanide in the specific context of burning composites.