Flame spread of paper sheets containing suppressants.

The flame spread rates of paper sheets, in which powder retardants were applied, were measured. Retardant compounds utilized were NaHCO3, Na2CO3, water, urea, NH4H2PO4, and HPO3. This paper forcuses mainly on the effectiveness of NaHCO3. As NaHCO3 content in the paper sample increased, the spread rate (2.5 mm/s) by flaming was gradually reduced and propagation by flaming was impossible at a content of 0.6 % by weight. Beyond the ustable region of 0.25 % to 1.6 %, only a spread by smoldering was possible and the spread rate (0.6 mm/s) continued to increase slightly up to 16 %. Although NaHCO3 is known to be a powerful suppressant for combustion reaction, its inherent ability effect on carbon combustion by alkali metal compounds causes a blowoff of the diffusion flame attached to the paper sample.