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Several studies have attempted to determine the lower limit of atmospheric oxygen under which combustion can occur; however, none have been conducted within a fully controlled and realistic atmospheric environment. We performed experimental burns (using pine wood, moss, matches, paper, and a candle) at 20°C in O 2 concentrations ranging from 9 to 21% and at ambient and high CO 2 (2000 parts per million) in a controlled environment room, which was equipped with a thermal imaging system and full atmospheric, temperature, and humidity control. Our data reveal that the lower O 2 limit for combustion should be increased from 12 to 15%. These results, coupled with a record of Mesozoic paleowildfires, are incompatible with the prediction of prolonged intervals of low atmospheric O 2 levels (10 to 12%) in the Mesozoic.

A new polyethylene paper may be marked on a hard surface with an ordinary oversize ball-point pen or dull pencil point. Where the paper is marked, a raised-line imprint appears on the same side of the paper as that used for writing. This imprint may be both felt and seen. Newly blinded and partially sighted persons are able to read ordinary Arabic letters and numerals after a few trials.