Limiting conditions for flame spread in fire resistant fabrics

Fire resistant (FR) fabrics are used for astronauts, firefighter and racecar driver suits. However, their fire resistant characteristics depend on the environmental conditions and require study. Particularly important is the response of these fabrics to varied environments and radiant heat from a source such as an adjacent fire. In this work, experiments were conducted to study the effect of oxygen concentration, external radiant flux and oxidizer flow velocity on the concurrent flame spread over two FR fabrics: Nomex HT90-40 and a Nomex/Nylon/Cotton fabric blend. Results show that for a given fabric the minimum oxygen concentration for concurrent flame spread depends strongly on the magnitude of the external radiant flux. At increased oxygen concentrations the external radiant flux required for flame spread decreases. Oxidizer flow velocity influences the external radiant flux only when the convective heat flux from the flame has similar values to the external radiant flux. The results of this work provide further understanding of the flammability characteristics of fire resistant fabrics in environments similar to those of future spacecrafts.