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It's well known that activated charcoal is an adsorbent and due to very big surface area per unit of mass it can adsorb a lot of particles.

Let's take as an example for my question this product on Amazon.

My questions are the followings:

  1. How much do this apply to the air purifiers? According to them it is supposed to work as an air purifier but I don't see it working unless the air you want to purify is being pushed through a activated charcoal filter. AFAIK by itself the activated charcoal is not attracting the smelly particles. Or is it?

  2. I have read that activated charcoal adsorbs bad smells(gases from air) and when the activated charcoal is placed in a hot environment it releases the adsorbed gases. What is that temperature at which adsorbed gases are released back in the air? Is this why they advice placing the product in the sun? Taken from product description: "Placing activated bamboo charcoal bag in the sun for 2 hours once a month, naturally rejuvenates the charcoal by removing excess moisture - extending the life of these charcoal room odor absorbers for up to 2 years."

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  1. Agreed: unless air is pushed through the activated charcoal bed, few impurities would be adsorbed.
  2. It would depend on how tightly the substance clings to the carbon, i.e. it would vary with impurity, but Trox Technik KS Filters recommends, "saturated activated carbon is reprocessed... with a gradual increase of temperature from 20 to 830 °C and a delay period of approximately 30 minutes."
  3. Finally, how long does the air-stream remain in contact with the filter? It would seem that most air bypasses the pores of the carbon on inexpensive commercial air filters. Activated charcoal might be of more use in reducing foul odors in a closed container, such as bottles of medicines.
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