Flammability of Human Hair in Exploration Atmospheres 2009-01-2512

To investigate the flammability of human hair, a series of normal and microgravity flame spread tests over human hair were performed in a low-speed flow tunnel to simulate spacecraft ventilation flows (∼20 cm/s). The tunnel atmosphere pressure and oxygen concentration was varied over the range of anticipated exploration atmospheres (21–34% O₂ in N₂, 8–14.7 psia). While hair is marginally flammable in air, spreading upward but not downward, it burns extremely well at or above 30% O₂ in any direction or g-level. The spread is characterized by a quick spread over the surface ‘nap’ or ‘frizz’, followed by continued bulk burning. Two hair ‘styles’ were tested — short hair and long hair — and style does not seem to affect initial nap spread significantly.

Opposed and concurrent nap spread rates are similar in 0g under comparable conditions. Oxygen concentration has a strong effect on flame spread rates. Concurrent spread rates are more than an order of magnitude faster in 30% O₂ compared to 21% O₂. Gravity also affects flame spread, with 1g concurrent (upward) being the fastest spread. For concurrent spread, 1g spread is faster than 0g spread, so it is reasonable to assume Lunar and Martian environments would also support faster concurrent flame spread. Surprisingly, however, for opposed flow, 0g spread is faster than 1g (downward) spread, so the generalization to Martian and Lunar environments cannot be made for opposed flow. Pressure has little effect on tip spread rate. Subsequent bulk burning appears weaker at lower pressure.