Activated carbon is an extremely porous black carbon allowing the absoption of molecules from chemicals thanks to the high degree of microporosity (less than 2 µm).
Based on the chemicals you have to filter, activated carbon can be impregnated to improve the absoption capacity. A specific impregnation could fit for one product and be unadapted for another one.
Hepa filter (High Efficiency Particulate Air) is an air filter with a very high efficiency.
The Hepa filtration efficiency is controlled and approved according to the norm NF EN 1822 and divided into 5 efficiency classes. The H14 Hepa filter which is the most efficient will stop 99,97% of the particles whith a diameter equal or bigger than 0,3 µm.