Low Ash content is desirable. Again, look for coconut shell carbon here. These two characteristics in themselves are not ideal, but they are indicative of other desirable qualities. Tests have proven that properly prepared coconut shell carbon have the most needed qualities for air purification. Carbons prepared from wool, lignite, pulp wastes and other softer materials are completely unsuitable for air purification applications.
Density is of consideration when comparing activity test results on a weight basis.
Small pore size represents a high surface area within the carbon granules and is better suited for air purification. The two most common tests used to rate activated carbons are the U.S. Government Accelerated Chloropicrin Test. The higher the results of the tests the greater the degree of total adsorptive capacity. However, it is important that the majority of the absorptive surface be comprised of pores that are slightly larger than the molecules to be adsorbed. Pore size is important for contaminant specific applications.