By: Tamara Middleton, Sales Representative – Architectural Products
ASTM E84 Standard Test Method for Surface Burning Characteristics of Building Material compares the burning behavior of a material with that of a select grade red oak. This test involves a sample of material in a tunnel with a flame held at one end and a draft applied. The flame is held for 10 minutes, smoke and flame spread are measured. This is basically stage two of the three stages of fire growth. A fire starts with the non-flaming stage then progresses to well-ventilated flaming and finally to under-ventilated flaming.
ASTM E84 tests the characteristics of insulation under the well-ventilated flaming stage, and well-ventilated fires are generally small and extinguishable, however fires in enclosed buildings can rapidly grow into under-ventilated fires. At this point the fire is large and becoming quite toxic.
Using the steady state tube furnace, toxic yields were determined for several types of building insulation, three of them were Expanded Polystyrene (EPS), Polyisocyanurate (PIR), and Polyurethane (PUR). The insulations were tested under smoldering conditions and flaming conditions. It was found that the levels of Carbon Dioxide (CO2), Carbon Monoxide (CO) in the smoldering EPS were below the limits of detection, and 0.003mg/g Hydrogen Cyanide (HCN). The PUR yielded 19.324 mg/g of CO2, 1.6mg/g of CO and .056mg/g of HCN, while the PIR yielded 25.39 mg/g of CO2, 2.171mg/g of CO and .083mg/g of HCN. Under flaming conditions the EPS with its high content of carbon produces more CO2 than the other two insulations, however the CO2 yield in all three decreases at the fire progresses from well-ventilated to under-ventilated as the oxygen level decreases. The CO levels increase in all three insulations at the fire progresses. The HCN yield for both PUR and PIR increases significantly as the fire progresses, while the HCN yield for EPS remains nearly undetectable.
In short all of the above insulations yield high levels of CO2 when burning in stage two, however once in stage three or under-ventilated burning, only the Polyisocyanurate and Polyurethane yield high levels of Hydrogen Cyanide.