Positive Responses to Negative Statements About PVC: Part 5

Statement: “PVC building products create poisonous gasses when they burn.”

The facts: This is technically a true statement, but misleading, because it is true about all organic materials (containing carbon), whether natural or synthetic, and there are countless organic materials in every commercial building. The major gaseous products of the combustion of PVC are carbon monoxide, carbon dioxide, hydrogen chloride and water. Chlorine gas is never produced when PVC burns.

But unlike other building materials, PVC is resistant to ignition; most rigid and flexible PVC will not burn without the continued application of heat from another source. The temperature required to ignite PVC is more than 300°F (150°C) higher than that required to ignite wood. The potential for flame to spread from burning PVC is very low because it has a slow rate of heat release, and it does not drip when it burns; instead, it develops a char which inhibits the spread of flame.

When it comes to structural fires, the U.S. Green Building Council’s Technical and Scientific Advisory Committee (TSAC), in its February 2007 report, Assessment of the Technical Basis for a PVC-Related Materials Credit for LEED, admits that there are many sources of toxic gases besides PVC. The report advises that “any firefighter not using a breathing apparatus would be taking on unnecessary risk, regardless of the specific materials present.” There is evidence that – as do many other building materials – PVC may contribute to hazardous conditions in building fires. However, there is insufficient information to determine how widespread or consistent the risks are. The TSAC report goes on to say that “compared with other plastics, and other combustible materials, PVC may have a beneficial role in reducing injuries in structural fires, as it may reduce the chances of a fire igniting or spreading due to its relatively high ignition temperature.”

In our final installment, we’ll look at this statement: “PVC is the largest source of dioxin, the most poisonous chemical on earth.”