Activated charcoal filters using CarbonWeb® 30 and CarbonWeb® 90 activated charcoal filter media. 1/2″ and thinner filters are CarbonWeb® 30 and 1″ thick filters use CarbonWeb® 90. These CarbonWeb® activated charcoal filters are more efficient than other types of activated charcoal filters. Charcoal filters should be used as “after” filters, not as prefilters. The reason is that particulates will fill the pore spaces in the carbon pieces and prevent them from collecting the vapor molecules they are designed for.