Expanded Polystyrene (EPS), commonly known by the trade name Styrofoam, is a petroleum-based plastic foam used widely for insulation, packaging, and disposable containers. This material is composed of a polymer matrix that is predominantly air—up to 98%. Despite its low density, EPS is combustible. Because it is an organic, hydrocarbon-based product, its flammability is comparable to that of other common organic materials like wood or paper.
The Combustion Process of Polystyrene Foam
When expanded polystyrene is exposed to heat, it undergoes a distinct physical transformation called thermal decomposition rather than immediately bursting into flames. The material first begins to shrink and soften above 100°C. As the heat intensifies, the foam collapses and melts into a highly viscous, liquid state.
Melting occurs well before ignition, as the polymer typically needs to reach a transfer ignition temperature of 360°C to 400°C to sustain a flame. Once ignited, the combustion process is characterized by an intensely hot, sooty flame. The molten plastic is hazardous because it drips away from the main fire.
These flaming, liquefying droplets flow across surfaces, rapidly spreading the fire to other combustible materials. Although the foam’s low density means a small actual plastic mass is present, it still releases a significant amount of heat. Burning continues until the entire mass of the foam is consumed.
Hazards of Styrofoam Smoke and Fumes
The primary danger associated with burning polystyrene is the thick, noxious smoke and fumes it generates. As the plastic undergoes incomplete combustion, it releases a complex mixture of gaseous byproducts and particulate matter. The most immediate threat is carbon monoxide (CO), an odorless, colorless gas that interferes with the blood’s ability to carry oxygen, potentially leading to unconsciousness and death.
Another compound released is the styrene monomer, the chemical building block of polystyrene. Styrene is classified as a hazardous air pollutant, and exposure to its fumes can cause irritation to the eyes, skin, and respiratory system. Inhaling this smoke exposes individuals to this toxic chemical, which is identified as a possible human carcinogen.
The fire also produces dense, black smoke composed of fine carbon particles, known as soot or particulate matter. This thick smoke can severely obscure visibility, hindering evacuation efforts during a building fire. Furthermore, inhaling these tiny particles can lead to respiratory distress and long-term lung issues, such as chronic cough and a reduction in lung function. The combination of toxic gases and heavy smoke makes exposure to burning polystyrene fumes a significant health risk.
Fire Safety and Proper Disposal
Given its flammability and toxic combustion products, intentionally burning expanded polystyrene for disposal is advised against. Setting the foam on fire releases pollutants directly into the environment and poses an uncontrolled fire hazard due to the material’s dripping behavior. Therefore, it is important to store the material away from open flames, fireplaces, heaters, and other high-temperature sources.
For proper management, the best approach is to avoid sending the material to a landfill, where it can persist for centuries. While technically recyclable, most curbside programs do not accept polystyrene due to processing difficulties and the high potential for contamination. Individuals should check with their local waste management service for specialized recycling programs or drop-off locations.
If a specialized recycling facility is available, the foam must be clean and free of food residue, dirt, and tape to be processed. Many communities and private companies offer collection events or specialized centers for EPS recycling. Reusing the material for packaging, craft projects, or donating packing peanuts to shipping stores are also effective methods to divert it from the waste stream.