Frequently Asked Questions about PVC Roofing Systems: Part 5

Q: Isn’t PVC a major cause of dangerous toxic gases during accidental building fires?

A: Every organic substance that burns during accidental building fires is a source of toxic gases. In fact, the mix of gases produced from PVC combustion – carbon monoxide, carbon dioxide, hydrogen chloride (HCI) and water – is very similar to those of all other organic materials. More importantly, vinyl’s inherent flame resistance properties actually play a beneficial role in mitigating the spread and strength of accidental building fires. Most rigid and flexible PVC will not burn alone without the application of heat from another source. Studies in Europe and the U.S. have shown that dioxin is present in all large-scale accidental fires, whether vinyl is present or not. PVC roofing membranes are a very small component of the mass of any building, and the smoke produced in a roof fire typically is external to the building.

Q: Isn’t PVC made from chlorine, one of the most dangerous substances on earth?

A: In its common elemental form (CI2 or dichlorine), chlorine is a poisonous, pale green gas about 2.5 times as dense as air. This is why the safe production, transportation, and handling of dichlorine is tightly regulated by government and vigilantly administered by industry through training and programs like Responsible Care. However, chlorine is also a naturally occurring element found throughout the oceans and rocks of the world, and it is an essential nutrient for plants, animals and humans. The chlorine used to make vinyl is derived from salt – both sea-water and land-based. Once chlorine is processed into vinyl, it is chemically locked into the product more tightly than it is in salt. Chlorine gas is never produced when PVC burns. When vinyl is recycled, landfilled or disposed of in a modern incinerator, no chlorine gas is released into the atmosphere. PVC roofing products are made from a very stable chlorine compound, and no chlorine is ever emitted from the finished product.

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