Global Equivalence Ratio Concept and the Prediction of Carbon Monoxide Formation in Enclosure Fires.
Global Equivalence Ratio Concept and the Prediction of
Carbon Monoxide Formation in Enclosure Fires.
Pitts, W. M.
NIST Monograph 179; 171 p. June 1994.
Available from: National Technical Information Service
Order number: PB94-207511
carbon monoxide; enclosures; building fires; compartment
fires; fire gases; global equivalence ratio; kinetic
models; pyrolysis; reduced scale enclosures;
This report summarizes a large number of investigations
designed to characterize the formation of carbon
monoxide (CO) in enclosures fires - the most important
factor in fire deaths. It includes the first complete
review and analysis of the studies which form the basis
for the global equivalence ratio (GER) concept. Past
and very recent (some as yet unpublished) investigations
of CO formation in enclosure fires are reviewed. Based
on the findings, two completely new mechanisms for the
formation of CO, in addition to the quenching of a fire
plume by a rich upper layer which is described by the
GER concept, are identified. The first is the result of
reaction between rich flame gases and air which is
entrained directly into the upper layer of an enclosure
fire. Detailed chemical modeling studies have shown
that CO will be generated by these reactions. The
second is due to the direct generation of CO during the
pyrolysis of oxygenated polymers (such as wood) which
are located in highly vitiated, high temperature upper
layers. The findings of these studies form the basis of
an analysis which provides the guidelines for when the
use of the GER concept is appropriate for predicting CO
formation in enclosure fires. It is concluded that
there are limited conditions for which such use is
justified. Unfortunately, these conditions do not
include the types of fires which are responsible for the
majority of fire deaths in building fires.