ASTM requires the use of SI units in all its publications and their use in reporting atmospheric measurement data. However, there are historic data and even data currently reported that are based on a variety of units of measurement. This practice tabulates factors that are necessary to convert such data to SI and other units of measurement.

does not list all the conversion factors commonly used in air pollution and meteorological fields. This practice supplements .

The values reported here were obtained from a number of standard publications. They were adjusted to five figures and organized in a rational order. All values reflect the latest information from the 16th General Conference on Weights and Measurements held in 1979.

The factors in Table 1 are provided to change units of measurement from one system to related units in other systems, as well as to smaller or larger units in the same system.

Values of units in the left column may be converted to values of units in the right column merely by multiplying by the conversion factor provided in the center column.