Powdered activated carbon (PAC) PAC is fine activated carbon material. PAC is manufactured by crushing or grinding carbon particles, 95–100% of which will pass through a 80-mesh sieve (0.177mm or smaller) as per ASTM standard. It is not advisable to use PAC in a dedicated vessel due to the possibility of high head loss. PAC is generally added directly to pocess units, such as raw water intakes, rapid mix basins, clarifiers, and gravity filters.