Air filtration in the human nose

You may have heard that our noses can offer some protection against pollutants in our breathing air. While this certainly is true to a degree, the human nose cannot filter everything. Let’s discover what, exactly, our noses can filter and what they cannot, and how we can keep our bodies safe from harmful pollutants.

The nose’s role in respiration

When you breathe through your nose, the air inhaled enters your nasal passages through the nostrils. Nasal passages are the two sections that direct inhaled air to the nasal cavity, an empty area located above the bone that forms the roof of the mouth. It is here where each breath is filtered of larger particles, humidified, and warmed before continuing down into the trachea and into the lungs¹.

Your nose filters the air, catching and trapping particles with the many small hairs in your nose to immediately filter out larger particles before they can access your lungs. Your nose also humidifies the air, adding moisture to keep your airways from drying out. And, finally, your nose warms the air to your body temperature before it reaches your lungs.

How the nose filters particles

Our airways are lined with a sticky mucus that acts as a flytrap to trap large pollutants and allergens. How does this work? Due to the shape of the nose, air that passes through it quickly changes direction; the air is diverted to a 90 degree angle as it passes from the nostril into the nasal cavity. This sudden directional change and the slowing of airflow as it moves from nostril to nasal cavity results in a deposition of particulate matter onto the sticky surface inside the nose.⁴

This mucus is then swept away by cilia, or tiny hairs, that push the mucus into the stomach where it is neutralised. Our bodies can create up to one litre of mucus per day!² This is an incredibly clever adaptation to avoid contaminants from reaching our lungs.

Mouth-breathing

Unfortunately, when you have a cold or are performing vigorous exercise that causes you to breathe through the mouth (mouth-breathing), air bypasses our natural filtration and conditioning system. This allows the air to access the lungs directly, leading to damage of delicate tissues.

What does the nose filter?

The human nose can generally filter out particles larger than 0.5 µm. Particles greater than or equal to this size include some of the following:

•       Pollen
•       Pet dander
•       Human sneezes
•       Asbestos
•       Emissions from vehicles
•       Mould and spores
•       Some smoke*
•       Some dust*

*The reason why not all smoke nor all dust is filtered is because their sizes vary greatly. The same goes for bacteria: the nose may be capable of filtering some, but not all, bacteria, depending upon their size⁴.

Particles that are smaller than 0.5 µm (also known as fine particles, particulate matter, or PM) that are generally not filtered by the nose include cigarette smoke, smoke from natural sources such as forest fires, viruses like COVID-19, and products of combustion. These particles pass with ease through the airway and into the lungs⁵.

How can we protect our respiratory system from pollutants?

While you cannot control the contents of the air that enters your nasal passage, there are steps that you can take to maintain a healthy nose and to ensure it is working at maximum capacity to limit larger particles from reaching your lungs. For example, one of the best things you can do is to stay well hydrated. By drinking lots of water, you can keep mucus thin and fluid which will help your body send trapped pollutants to the stomach where they can be neutralised.

Here are some more regular habits you can follow to keep your nose healthy (these tips can even reduce the risk of asthma attacks for asthma sufferers):

• When it is cold outside, wear a scarf to protect your nose and mouth from the drying effects of cold air
• Use saltwater nasal washes to keep nasal pass ages moist if exposed to dry air or pollutants
• Avoid using too many decongestant sprays which can cause damage to the cilia in your nose
• Verify with your healthcare professional before taking any new medications that it will not lead to nasal problems (i.e. some blood pressure and anti-anxiety medications may cause nasal dryness)
• Wear a mask on planes to avoid breathing in dry cabin air
• Maintain a healthy diet and exercise
• Avoid first-hand, second-hand, and third-hand smoke
• Do not completely remove nose hairs: they are your body’s filters!
• Keep allergens low in your home by dusting and washing bed sheets regularly²

As previously mentioned, your nose cannot protect you from particles smaller than 0.5 microns. This includes cigarette smoke and particularly dangerous fine particles that, due to their small size, can enter the body through the respiratory system and gain easy access to the bloodstream, giving them a direct route to the rest of the organs in the body including the brain and heart which can have a serious impact on your lifespan. A method that works to protect yourself from fine particles is to wear an FFP2 mask, but as many of us know as a result of the COVID-19 pandemic, masks are uncomfortable and impractical to wear all day long. Fortuntately, there is another way you can protect yourself against particles of all sizes: equip your home and office with an air purifier.

Ensure better breathing with Eoleaf

Eoleaf’s air purifiers contain 8 different filtration technologies, including a HEPA (high efficiency particulate air)-certified filter. This filter removes, in a single pass, at least 99.97% of particles of a size greater than or equal to a diameter of 0.01 µm. Our air purifiers also contain activated carbon filters which are effective at filtering out volatile organic compounds (VOCs), another class of pollutants that may not be filtered out by the nose. With our products, you can ensure that you are breathing the freshest, pollutant-free air possible, protecting your health from the dangerous effeects of airborne contaminants.

Reach out to our team of air purification experts today to start breathing purer air thanks to an Eoleaf air purifier.

References

¹ NCI Dictionary of Cancer terms. National Cancer Institute. (2023). Retrieved February 20, 2023, from https://www.cancer.gov/publications/dictionaries/cancer-terms/def/nasal-cavity

² Your nose: The ultimate air cleaner. Allergy & Asthma Network. (2023). Retrieved February 20, 2023, from https://allergyasthmanetwork.org/news/your-nose-the-ultimate-air-cleaner/

³ Eccles, R. (2013). The nose and control of nasal airflow. Middleton’s Allergy, 640–651. https://www.sciencedirect.com/science/article/abs/pii/B9780323085939000413?via%3Dihub

⁴ How do we breathe?. Otrivine. (2022). https://www.otrivine.co.uk/nasal-health/how-do-we-breathe.html

⁵ What your amazing nose can filter! Breathing Retraining Center. (2023). Retrieved February 20, 2023, from https://breathingretrainingcenter.com/what-your-amazing-nose-can-filter/

⁶ Schwab, J.-A., & Zenkel, M. (1998). Filtration of particulates in the human nose. The Laryngoscope, 108(1), 120–124. https://onlinelibrary.wiley.com/doi/abs/10.1097/00005537-199801000-00023