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Smoke Toxicity and Epidemiology

All combustible materials produce toxic smoke when burned. Smoke may typically include a variety of combustion byproducts, such as hydrochloric acid, ammonia, carbon dioxide, carbon monoxide, hydrogen sulfide and hydrogen cyanide. According to the U.S. Fire Administration (USFA), smoke is the killer in 60% to 80% of all fire deaths.

In terms of relative hazard, carbon monoxide (CO) is typically the most abundant toxic component released by fires under almost all combustion conditions and is responsible for most deaths in fires. It is released by the incomplete combustion of any material containing organic material (material primarily composed of carbon, hydrogen and oxygen) such as wood.

Materials containing nitrogen will generally produce hydrogen cyanide and nitrogen oxides. Common products that contain nitrogen include household ammonia, sheep’s wool, cotton, paper, silk and composite wood products using polyurethane binders.

Smoke and combustion byproducts from fires are toxic regardless of the source of those fires and what is being burned.

The hazards created by any burning material are strongly dependent on the fire scenario, a complex situation influenced by a range of factors, such as room size, temperature, ventilation conditions, exposure time, source and location of ignition.

Plastic materials in the building envelope are typically installed and protected from fire within walls, roofs or floor/ceiling assemblies. These assemblies are tested for compliance with requirements for flame propagation and penetration by fire. Because of their containment within the building envelope assemblies, combustible building materials are typically among the last products exposed to a fire.

The nature, frequency and duration of exposure to smoke toxicants will determine any long-term health effects. For most people, significant exposure to fire gases is a single lifetime event, if ever. When people can escape from a fire or are rescued, they will normally recover fully after a short period of time and with prompt medical care. As with many other hazards, individuals already suffering from compromised cardiac or pulmonary systems are more susceptible to fire gases. Populations encountering fire events more frequently require special protective equipment. For example, firefighters are required to wear breathing protection when in the immediate vicinity of fires. Their long-term exposure to smoke toxicants is reduced through diligent use of personal protective equipment (PPE) and safe work practices.