What is Activated Carbon?

What is Absorption and Adsorption?

Many times we see the statement: "Activated Carbon absorbs airborne odors and vapors." This is not a true statement. A true statement is: "Activated carbon adsorbs airborne odors and vapors." Do you see the difference? The word adsorb is important here. When a material adsorbs something, it means that it attaches to it by chemical attraction. The huge surface area of activated carbon gives it countless bonding sites. When odors and vapors pass next to the activated carbon surface, they attach to the surface of the carbon. They are added to the surface of the carbon, they are not absorbed by the carbon. They are adsorbed. To be absorbed by carbon the odors and vapors would have to be diffused into the carbon, not simply attached to it's surface. Carbon DOES NOT absorb, it adsorbs!

Here is a good example of the difference between the words "ABsorb" and "ADsorb":

If you have a cake and eat and swallow it, you are ABsorbing it. If someone throws a cake in your face, your face ADsorbed it!

Here is another one: If you use a sponge on your counter to clean up spilled milk and cookies, the milk is ABsorbed into the sponge. The cookie crums are ADsorbed to the outside 0of the sponge!

So, in air cleaning with carbon you NEVER ABSORB anything into the carbon. You ADSORB it onto the surface of the carbon!

Many natural substances are used as the base material for producing carbon. The most common base materials used are wood, coal and coconut shell. These base materials are subjected to a process called carbonization. Carbonization is a heating process where by the base material is subjected to high temperature which drives out any volatiles. To activate the carbon it is subjected to a second heat and steam treatment. The activation of the carbon is what gives it it's unique adsorption characteristics. The activation of the carbon creates carbon which is highly porous providing a large surface area of the carbon for adsorption..

Are ALL Activated Carbon filters the same?

NO! Activated carbon can be enhanced and impregnated and/or custom blended to be a more specialized adsorbant. For an example: Using standard Activated Carbon (such as used for common household odors) is NOT effective in a Beauty Salon where ammonia and formaldehyde fumes are. The Activated Carbon for a Beauty Salon would be enhanced for those specific pollutants found in a Beauty Salon.

Does it matter how much activated carbon there is?

YES! Activated carbon adsorbs to it's surface. When there is no more surface left to adsorb to the carbon it is depleted of it's capability to be effective. Large amounts of carbon will last longer then small amounts because it has larger amounts of surface area for adsorption. Also, depending on amounts of pollutants being adsorbed, a small amount of carbon can be depleted within weeks making it useless.

Does it matter how thick an activated Carbon filter is?

YES! The more contact time the activated carbon has with a pollutant, the better chances of it adsorbing it. The thicker the carbon filter the better it's adsorption. If the pollutant has to go through a long maze of activated carbon it's chances are also greater of being adsorbed.

Which is more effective, a pad impregnated with carbon or granular activated carbon?

Granular Activated Carbon is more effective then a 1" or 2" thick impregnated carbon pad. Granular activated carbon will have much more surface area for adsorption than a impregnated pad. Also, an impregnated pad will have to be changed much for frequently then a canister of activated carbon. Keep in mind that the contact time the carbon has with a pollutant is less in a pad so it's adsorption rate is also less.