What term describes toxic atmospheres created by smoke and heat?

The term "Immediately Dangerous to Life and Health" refers specifically to conditions where the level of toxic substances in the atmosphere poses an immediate threat to a person's health or safety. This often occurs in environments filled with smoke and heat, such as during a fire situation, where inhalation of smoke can lead to serious respiratory problems, poisoning, or even death. Knowing that these atmospheres are dangerous allows firefighters to take necessary precautions, such as wearing specialized breathing apparatus, to ensure their safety while operating in such hazardous conditions.

Other terms like "Hazardous Materials" or "Toxic Substances" are broader categories that may include various chemicals or agents that can be harmful but do not specifically describe the immediacy of the danger. "Life-threatening Environments" might indicate danger but lacks the specific context of immediacy associated with health and life that is critical during emergency situations in firefighting.