Air-Drying Oven—A device for passing slightly heated
air over the sample. The oven should be capable of maintaining
a temperature of 10 to 15°C (18 to 27°F] above ambient
temperature with a maximum oven temperature of 40°C
[104°F] unless ambient temperature is above 40°C [104°F], in
which case ambient temperature shall be used. In the case of
easily oxidized coals, the temperature should not be more than
10°C [18°F] above ambient temperature. Air changes shall be
at the rate of one to four per minute. A typical oven is shown
in Fig. 2.