limiting oxygen index values of single and multilayer proban cc- and pyrovatex cp-flame retardant finished cotton fabrics having a variety of area densities were determined as a function of igniter application time and temperatures up to 200 $degree$ c. except for the lightweight (140 g m** $minus$ **3) proban cc-treated fabrics, loi, like comparable extinction oxygen index (eoi) values, increased as ignition times were increased from 2 to 10 s. extrapolation to zero ignition time enabled $left bracket$ loi $right bracket$ //0 values to be determined at each temperature, which, for a given flame retardant, increased linearly with area density of mono- and multilayered fabric combinations. comparison with earlier extinction oxygen index results showed that this $left bracket$ loi $right bracket$ //0 vs. area density dependence had significantly lower correlation than that for $left bracket$ eoi $right bracket$ //0 (edited author abstract) 16 refs