With the incredible number of new masks reaching the market there are many brands looking to get competitive advantages. This means that there are always new technologies being implemented in the field. Although not a new technology, activated carbon filters are a way that many brands are trying to beat their competition and differentiate their mask.
Masks such as Cambridge Mask have long advertised their use of activated carbon filters. More recently, masks such as Bloo Mask have implemented the technology in an even better way, making a mask that can greatly reduce odours. You can even purchase replaceable that feature a carbon layer.
However, although all of these masks feature carbon filters, very few of them actually explain the benefits or downsides of using such a filter. Typically the stick to marketing language such as ‘military grade’ rather than actually explaining the purpose of such a filter.
With that being said, in this article I plan to look into exactly what carbon filters in masks do. In this article I will cover the basics of carbon (and activated carbon) filters, what they filter, how effective they are, and also what they don’t filter.
If you want to learn more about the more advanced filtration aspects of filters I recommend checking out this article on most penetrating particle sizes. Further, if you have any questions regarding carbon filters that weren’t covered in this post, please feel free to contact me or leave a comment on this post.
Finally, I want to mention that I am not an expert on activated carbon. This post was written after a lot of research. If you notice an inaccuracies please let me know so I can update the article and keep it accurate.
This post contains affiliate links. For more information, please refer to my affiliate disclaimer.
Information on this blog is for informational purposes only. Readers are encouraged to confirm the information herein with other sources. Furthermore, this information is not intended to replace medical advice from professionals. This website assumes no responsibility for the accuracy of the information, which is subject to change without notice.
What Is Activated Carbon?
Carbon filters are made from many different forms of carbon. Most commonly, charcoal is used. However, carbon filters can come from many other forms including nutshells, wood, coal, and petroleum (Activated Carbon).
Once a source material is found, the carbon must be activated. This is done by burning the carbon without oxygen, resulting in charring. The charring is then treated further, developing interconnected pores (often microporous pores which are under 2nm in size) inside the carbon (General Carbon).
The carbon can be activated with a variety of different agents. The use of different agents will result in different performance and applicability of the carbon. The agent will either be mixed with the carbon or impregnated (the agent placed inside the carbon) (Springer). Impregnating is often considered superior as it allows the carbon to maintain its surface area allowing for higher adsorption.
The activation process greatly increases the surface area of the carbon. Massively so. In fact, with the rough textured surface and many pores, one gram of activated carbon can have an adsorptive surface area of 3000m² (APS Physics). In short, activated carbon is capable of adsorbing vast amounts of gas.
You may have noticed that I am using the word adsorb, and not absorb. This is not a mistake! Rather than absorbing gases, activated carbon actually adsorbs them, meaning that they stick to the surface. This is why the surface area of activated carbon is so vital.
Why Do Masks Use Carbon Filters?
Activated carbon (also called activated charcoal, or active carbon) is used to adsorb gases from the air (among many things). It is most effective at filtering volatile organic compounds (VOCs) and odours. In general, activated carbon will only filter organic (carbon based) chemicals. It is ineffective against non-organic chemicals.
Activated carbon is used for hundreds of different purposes in the modern world. It has great filtration capabilities, and as such it is often used for water treatment, pollution filtration, gas purification, and more. On top of this, activated carbon is generally considered safe and is not dangerous (WebMD).
Since most masks offer only particle filtration, a carbon filter is a useful addition. While this by no means makes a mask effective against gases, it does add an extra layer of protection that is welcome. Further, it can be quite effective at reducing smells that reach the wearer.
Due to the nature of filtration (through adsorption), activated carbon filters do have a limited lifespan. Once the surface area is full, they will no longer be able to remove pollutants from the air. While carbon can be reactivated, it’s normally impossible when they are fitted in a filter or mask.
What Does Activated Carbon Filter?
As mentioned above, activated carbon works best when filtering organic chemicals. Specifically, activated carbon is most effective against compounds that hold a high molecular weight and low solubility due to activated carbon having a high molecular weight as well (SentryAir).
It is worth noting that carbon filters do NOT filter particle pollution (including allergens such as dust and pollen). For this, a fibrous filter media will be needed. Luckily, most masks include a layer for particle filtration as well as a carbon filter.
What activated carbon is effective at filtering is volatile organic compounds (VOCs) and odours. Some common VOCs are Ethanol, Butanol, Acetone, Formaldehyde and Benzene. However, most masks will not fully filter these VOCs, but only partly filter. Further, if the mask is not fitted correctly it will not provide filtering.
On top of this, activated carbon filters are effective at filtering odours. This is especially useful in a mask, as it can not only decrease the smells the wearer will experience, but can also decrease smells on the mask itself.
Further, a recent study done has shown the masks that include a carbon filter (as well as a spun bound and melt blown filter) are much more capable at filtering common highway pollutants such as carbon, nitrogen, and sulphur oxides (COx, NOx, SOx) (Hindawi).
SentryAir has a full table that shows what the adsorption index of many different compounds are. I highly recommend referring to that for a more visual showing of the effectiveness of activated carbon filters.
What Does Activated Carbon Not Filter?
As previously mentioned, there are also many things that activated carbon does not filter. Activated carbon is usually only effective against organic compounds. Inorganic compounds (Compound that lack carbon–hydrogen bonds), will not be filtered.
However, there are some exceptions to this. Some inorganic compounds can be adsorbed, but usually they are adsorbed at a lower efficiency than organic compounds. Therefore, without going into specifics it is safer to assume that activated carbon will not filter inorganic compounds.
Also, as mentioned above, activated carbon does not filter particles. This is the reason why you will usually find that activated carbon filters are usually layered between other fibrous filtering layers which are intended to filter particles. An example is the Earth Filter spread shown above.
Most notably, activated carbon filters will NOT filter carbon monoxide. This very dangerous gas is not impacted by activated carbon filters and other filtration measures will be needed for protection.
Are Masks With Carbon Filters Better?
I would argue that yes, masks with carbon filters are better. However, this isn’t true in every case. A mask with a carbon filter will filter some potentially dangerous pollutants but this won’t be useful for everyone.
On top of this, typical cloth masks with carbon filters can’t truly be relied upon. Without a proper fitting mask (and fit testing), the seal of a mask will never be perfect, meaning that you won’t be fully protected from the pollutants anyway.
In saying that, masks with activated carbon filters can provide some level of adsorption where it would otherwise not exist. In other words, it’s extra protection with (often) no extra or little extra cost. Activated carbon filters also usually add little extra breathing resistance.
Perhaps a more realistic benefit for masks with carbon filters is that they can help remove odours from the air. At times this difference may not be that noticeable, but I did find a very significant difference while wearing the Bloo Mask with a carbon filter. Smells like tobacco smoke are largely neutralised before reaching the wearer.
In conclusion, the addition of an activated carbon filter to a mask or respirator is almost purely positive. There are no obvious downsides. The filter will provide protection against more pollutants while adding little to breathing resistance. However, carbon filters in cloth masks should not be relied upon to provide total protection from such substances.
Activated Carbon Filter FAQ
Why Do Masks Have Activated Carbon Filters?
Many masks use activated carbon filters for added protection against organic pollutants such as VOCs. Carbon filters are also capable of removing odours and preventing (or decreasing) smells such as tobacco smoke from reaching the wearing.
What Does Activated Carbon Filter?
Activated carbon filters are generally effective against organic compounds. They are often used as protection against volatile organic compounds (VOCs). They are also effective at filtering odours.
What Masks Have Carbon Filters?
What Doesn’t Activated Carbon Filter?
Activated carbon filters are not effective against particles (such as PM2.5 or PM10). They are also not effective against the majority of inorganic compounds – generally carbon filters are most effective against carbon-based pollutants.
Can Carbon Filters be Harmful?
Activated carbon filters are considered safe and activated carbon is used in many different fields from water purification to medicine.
What Is the Lifespan of Activated Carbon Filters?
Activated Carbon filters generally last a few months before needing to be replaced. However, this great depends on the airflow and size of the filter.
How Can I Tell When to Replace a Carbon Filter?
There is no visible way to tell when a carbon filter needs replacing. Sometimes you will notice a strong smell coming from the filter though. If that is the case, it may need replacing. Otherwise it is best to follow the manufacturers instructions.