For many of us, the smell of burning charcoal carries memories of backyard BBQ’s and happy days at the beach. But charcoal isn’t just for summertime fun. In fact, charcoal has been used for thousands of years for everything from painting to cooking to better digestion.

What is charcoal?

Charcoal is a carbon residue made by partially burning wood and other organic materials using a limited air supply. Because it’s dehydrated, charcoal burns much hotter than wood.

What’s the difference between charcoal and activated charcoal?

Activated charcoal is charcoal that has been heated to a very high temperature. Even though it sounds simple, the heating process actually results in an important chemical change.

When the temperature of the charcoal is raised, the elements and compounds that were bound with the carbon atoms are removed and all the binding sites for carbon become “free” for binding with other molecules and atoms, making activated charcoal much more porous than ordinary charcoal.

A good way to think of it is that charcoal is carbon and activated charcoal is charcoal that has been treated with oxygen to open up millions of tiny pores between the carbon atoms.

Why would we want charcoal to be more porous?

The fact that activated charcoal is more porous means that it’s much better at removing contaminants. Activated charcoal has been used to remove toxins from the water, bloodstream and even the digestive tract. In fact, hospitals often use activated charcoal to treat people who have ingested poison.

The porous nature of activated carbon makes it especially useful in trapping odors and volatile organic compounds (VOC’s) in the air. VOCs come from all sorts of different household products and can be really bad for your body. Activated carbon removes them through a process called adsorption.

Did you mean absorption?

Nope. In absorption, the substance you want to remove is pulled in to the structure of the absorbent, like a paper towel absorbing milk. The milk fills the spaces inside the paper towel, but never becomes part of it on a molecular level.

Adsorption, on the other hand, is a chemical process. So, the pollutants that enter actually stick to the outside of the carbon. As long as there is an open adsorption site (and, in activated carbon there are plenty), the pollutants will keep sticking to the carbon.

This process of adsorption makes carbon filters particularly useful in removing chemicals from the air.

How do you know when your carbon filter is saturated?

The first sign that your carbon air filter is saturated may be the smell. This happens because when the carbon is saturated, the chemicals have nowhere to go and are re-released into the air. Unfortunately, not all chemicals have odors and by the time the room smells bad, a lot of dangerous gases may have already been released into the air.

It’s generally a good policy to change your filters once a month.

So, as long as I have a carbon filter, I can be sure my air is clean?

No! While carbon filters do a good job of removing many kinds of gases and odors, they aren’t useful in getting rid of other kinds of particles like dust and pollen. True HEPA filters are your best option to keep your air free of those types of pollutants.

The best air purifiers use a combination of activated carbon and true HEPA filters to keep your air free of the full range of contaminants.