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Are Carbon Air Filters A Wise Investment?

Are Carbon Air Filters A Wise Investment?

When you walk in your front door, are you greeted with an overpowering odor that knocks you off your feet? Do you catch a whiff of a more subtle, yet unpleasant scent coming from a specific area in your home? Are you concerned that your indoor air is filled with contaminants? Whatever the case may be, you might be thinking about purchasing an activated carbon air filter to combat the problem. Before you invest in one, however, just like any other product you’d invest in, you probably have some questions. What exactly is an activated carbon air filter? How does it work? To find the answers to these questions and more and to determine whether or not an activated carbon air filter is the right choice for you, keep on reading.

What is Carbon Anyway?

Before jumping in and discussing what an activated carbon filter is, it’s first important to understand what carbon is. Also referred to as charcoal, carbon is a remnant of inadequate combustion. Imagine, if you will, a singed piece of wood left on the bottom of a fire pit after the fire goes out. This happens when only the readily flammable components in the wood have burned away as a result of inadequate oxygen or because of deficient heat. The charred black spots that are left on the wood is largely carbon.

On the industrial setting, the process of creating charcoal is accomplished by heating a material in an air-tight vacuum chamber, which allows all of the volatile compounds that are generated to be released, and the carbon is left behind. Several types of materials are used to make carbon. Wood is one of the most commonly used, but other materials can include coconut shells, tree park, lignite, or bituminous coal. As expected, each material creates a somewhat different type of charcoal.

What Makes Carbon Activated?

Carbon becomes activated when it undergoes an additional step during processing, which improves its ability to trap gas molecules. There are two methods that can be used to activate carbon.

  1. Chemical activation. This method of activating carbon involves submerging carbon into a bath of acid or chemicals. The temperature of the bath is heated up to a temperatures that range between 842 and 1,652 degrees F (450 to 900 degrees C). Of the two methods of activating carbon, chemical activation is the faster option; however, care does need to be exercised, as a great deal of adsorption (an accumulation of gas on the surface of the carbon) does occur in the heating chamber, which can result in impure activated carbon. Another downside is that the depending on the amount of acid or chemicals the carbon absorbs, it may be rendered useless.
  2. Gas activation. With this method of activation, carbon is heated in an airtight chamber while gas is pumped into it, which exposes the carbon to oxygen for oxidation purposes. The gas method of activation has to take place in an inert environment, where temperatures range from 1,112 and 1,652 degrees F (600 to 900 degrees C), and consequently, the temperature in the chamber is increased to between 1,652 and 2,192 degrees F (900 to 1,200 degrees C). This allows the oxygen to bond to the surface of the carbon.

How Does An Activated Carbon Air Filter Work?

So, now that you know what activated carbon is, let’s take a look at what an activated carbon filter works.

As the name describes, this specialized air filter is comprised of a layer of activated carbon, which features a large surface area and is highly porous. Due to the highly porous nature of the activated carbon, this type of filter can absorb a great deal of large air particles and fine particulate matter. It removes airborne contaminants via adsorption, a process that attracts compounds that would otherwise circulate through the air. Adsorption may sound like absorption, but it’s important to note that the two terms mean very different things. Absorption refers to a process that traps matter into an absorbent material, and adsorption refers to a process that involves pollutants sticking on the exterior of the carbon molecules. This is where the activation process that is used to create activated carbon comes in useful, as it increases the adsorption surface of the carbon molecules, thus increasing the purification capacity of the filter. Remember the lattice work of carbon molecules that were mentioned earlier? Well, that’s what the gases from the air are trapped in within an activated carbon filter.

Carbon Filters and the Process of Adsorption

In order to understand how carbon filters work, it’s important to understand how the process of adsorption works. Therefore, to further explain the process of how an activated carbon air filter works, when air flows through a carbon filter, every molecule within the air flow through the activated carbon, too. Some of the molecules are trapped with the carbon, which is known as adsorption.

The process of adsorption occurs when a particle gets trapped on the surface of a material. The more surface area available, the greater the chances are that a particle will get stuck on the surface of the activated carbon filter. While absorption is similar to absorption, there is one key difference between the two processes. Adsorption occurs when a particles gets trapped to the surface of a material, while absorption occurs when a particle gets trapped inside the material.

The Rich History of Carbon Air Filtration

How is it that people came to learn that activated carbon is an effective way to filter contaminants? It is believed that humans first used this type of filtration as a way to remove impurities from smelted metal when bronze is manufactured. Historical evidence suggests that ancient Egyptians were the first to use activated carbon for medicinal purposes as a way to extract odors that were linked with infections. It is also known that between the 16th and 18th centuries, sailors often kept their drinking water in wooden barrels that were either charred with or smeared with charcoal along the inside, which kept the water free of contaminants, providing them with access during their prolonged voyages.

During the Great War (World War I), the masks that soldiers wore were fitted with charcoal filters to remove some of the toxic gases that they were exposed to; however, the charcoal was only effective against some poisonous airborne materials. It wasn’t until post World War II that activated carbon was produced and used on a large scale, which eventually lead to the creation of the activated carbon filters that are used for air filtration, as well as for water filtration.

What Contaminants Do Activated Carbon Filters Trap The Best?

Activated carbon air filters are very effective at trapping minute particles that measure smaller than 0.3 micrometers in size. Hence, they do a very good job of removing pollutants that are gaseous in nature., such as:

  • Tobacco smoke. Tobacco smoke, whether from cigars, cigarettes, or pipes, contains more than 7,000 chemicals, and it is estimated that 250 of these chemicals, at minimum, have adverse health effects. Activated carbon air filters are very effective at filtering tobacco smoke. The particles that smoke is comprised of measure as small as 0.1 and 1 microns, which means that they can pass through a HEPA filter. Because activated carbon filters can trap particles that are as small as 0.3 micrometers, they are very effective at trapping smoke particles. Hence, if you or someone you love smokes, an activated carbon filter can come in very handy.
  • Volatile Organic Compounds (VOCs). VOCs are organic chemicals that, at room temperature, have a high vapor pressure, which correlates with a low boiling point and relates to the number of the molecules in the air that surrounds the sample, which is known as volatility. Volatility explains how readily a substance can vaporize; it is more likely that a substance with a high volatility, at a given temperature and pressure, will exist in a gaseous state, whereas a substance that has a low volatility is more likely to exist either in a liquid or a solid state. VOCs are what creates scents, as well as pollutants. Pollutants that are referred to as VOCs are at a molecular level and Picometers are used to measure them. Picometers are smaller than microns, and they are so miniscule that they can remain in the air for a prolonged period of time. A high-quality activated carbon air filter is the only way to remove VOCs from the air. Examples of some of the most common VOCs that frequently contaminate indoor air include:
    • Acetaldehyde. Produced as a result of burned wood or tobacco.
    • Benzene. Often comes from cleaning products, paint thinners, and glues.
    • Chloroform. Generated from chlorinated products, such as bleach. 
    • Formaldehyde. Many household items, such as building materials (insulation, etc.), rugs, carpeting, and furniture are treated with formaldehyde, which off-gasses into the air.
    • Napthalene. Generated by mothballs.
    • Styrene. Comes from plastic packaging materials, such as packaging wrapped around furniture, toys, or appliances.
    • Trichloroethylene. Spot cleaners, paints, and varnishes contain trichloroethylene.
  • Odors. Because they are capable of trapping such miniscule particles, activated carbon air filters do an excellent job at trapping odors. If you have pets, cook with ingredients that generate pungent smells, someone in your house smokes, your home has been infested with mold or mildew or if you just simply enjoy the scent of clean air, an activated carbon air filter would work well for you.

Different Types of Activated Carbon Filters

There are several different types of activated carbon air filters. Some of the most common types that are used to purify indoor air in homes include:

  • Granular Activated Carbon (GAC). This type of activated carbon filter is comprised of large granules that have a 3mm diameter; about the size of a grain of sand. Granular Activated Carbon filters have long services lives and can be used with other types of substances, such as zeolite. They’re very effective for eliminating odors and gaseous pollutants, such as formaldehyde.
  • Powdered Activated Carbon. This type of filter is comprised of granules that measure between 10 and 50 microns, and resins are used to bond them together, creating a large block. Because of the smaller particle size, powdered activated carbon air filters have a greater absorption capacity, both in terms of speed and height, than granular activated carbon filters.
  • Woven Carbon Filters. With a woven carbon filter, activated carbon is woven into rayon, creating a thin sheet that is used as a carbon filter in an air purifier. Woven carbon filters can also be used as standalone units that can be connected in areas where the air needs to be purified, such as garbage cans.
  • Treated Carbon Filters. This type of activated carbon filter is treated with potassium permanganate or silver, which increases its adsorption capacity; a process that is often referred to as impregnation. Impregnated filters can remove a significant amount of chemical gaseous pollutants, like formaldehyde and natural gas.

Are There Cons to Using an Activated Carbon Air Filter?

While activated carbon filters are highly effective for removing volatile organic compounds, there are some downsides, some of the most notable of which include:

  • Replacement. Like all other types of filters, activated carbon filters need to be changed, as eventually, they become contaminated, and are not only rendered ineffective, but instead of removing contaminants, can actually put pollutants back into the air. Filter replacement, however, can not only be difficult, but the cost can also be exorbitant. Determining when an activated carbon filter needs to be changed can be difficult, as it doesn’t display visible signs of complete saturation. While you can abide by the recommendations made by the manufacturer, if the air in your home contains high levels of contaminants, the filter could become saturated a lot faster than expected, and as such, you could continue using the filter long after it is no longer effective. Plus, as mentioned, activated carbon air filters can be quite pricy.
  • Unable to remove fine particulate matter. Though activated carbon air filters can remove odors and VOCs, they are unable to remove particulate contaminates, including common allergens, like pollen, dust mites, and pet dander. As such, if you suffer from allergies, an activated carbon air filter may not be able to alleviate the symptoms you experience.

Should You Invest in An Activated Carbon Air Filter?

It depends on your objective. For example, if you want to remove unpleasant odors from cooking or something burning, or perhaps you’re worried about VOCs that may be released into your home’s air as a result of household cleaning products or from furnishings, such as formaldehyde, an activated carbon air filter cold be beneficial. With that said, however, if you’re seeking long term air filtration for your home, an activated carbon air filer may not be the right choice for you. Not only is trying to figure out when to change out the filter tricky and costly, but it may not be able to offer the purification that you are seeking.

The Ideal Solution

If you want to maximize the cleanliness of your home’s indoor air quality, while using an activated carbon filter alone may not be the best option, that’s not to say that it is completely useless. You could use a combination of an activated carbon air filter and an air purifier that features HEPA filtration. Doing so would help to remove odors and VOCs, as well as smaller particles that are common sources of allergies, such as dander, pollen, and dust. Furthermore, you could take steps to improve the overall cleanliness of your home. For instance, mold is one of the most common sources of allergies, as the spores are airborne, and exposure to the tiny spores are known to cause a number of adverse health effects. The use of an activated carbon and a HEPA filter would help to remove those spores, but to properly address the problem, identifying instead of assuming that mold spores are present in your home is highly recommended. Doing so will allow you to identify the source of indoor mold growth and actually eradicate the problem. Therefore, routine mold inspections performed by a certified professional would be worth your while.

The professionally trained and highly experienced technicians at Mold Inspection and Testing, one of the most reputable indoor mold testing companies in the country, use the most advanced technologies and proven techniques and strategies to conduct comprehensive assessments. We’ll take both surface and air samples to determine if mold growth is a problem in your home, and if so, we will make recommendations to correct the issue. Regular mold testing combined with the use of activated carbon and HEPA filtration will allow you and your loved ones to enjoy the cleanest and healthiest indoor air possible.