Fire Safety Science Digital Archive

Experiments of flame spread over a filter paper treated with a solution of flame retardant, NH4H2P04 or NaHCO3, were conducted in an upward opposed air flow. The flame spread rate and temperature profiles of gas phase/paper surface were examined. Except promoted flame spread with small addition of NH4H2P04, these agents retarded the flame spread rate and reduced the critical flow velocity for spread. NH4H2PO4 decreased the pyrolysis zone temperature more than 100 K while NaHCO3, decreased 20 or 30 K at most. With increasing add-on rate, the flame leading edge location receded and also the flame stand-off distance increased. The leading edge practically corresponded to 1400 K isotherm tip. The slowly ascending flame temperature distribution near the leading edge, observed for NH4H2P04 addition, suggested diluted pyrolysis gas, and another type of flame temperature distribution observed for NaHCO3, addition suggested inhibition effects in flame reaction zone.