How Do Air Purifiers Work?

At a glance, an air purifier seems like a relatively simple piece of technology. It pulls in air from its surrounding environment, captures or destroys contaminants and then re-circulates the clean air.

However, have you ever stopped to wonder how it actually does that? After all, it’s removing contaminants smaller than we can see.

Therefore, it may come as a surprise that air purifiers take a lot of time and money to design and develop. They are dependant on advanced engineering and peak technology to be effective.

So, with that in mind, let’s look at how do they work and which type of purification is best.

Common air purification methods

Within air purifiers, there are many different methods of purification in active use. These vary between models and brands, and in many cases, multiple methods are combined for better results.

The most commonly seen methods in modern purifiers are:

  • Carbon filtration
  • Heat sterilisation
  • HEPA filtration
  • Particle filtration
  • Particle ionisation
  • Plasma sterilisation
  • UV sterilisation

These seven types of purification are the foundation of most high-quality air purifiers. Some are more effective than others, but ultimately they can all play a role in reducing levels of airborne contaminants.

Sterilisation vs filtration

As you can see from the above list, most air purifiers rely on either filtration or sterilisation as their primary purification method. So, what makes these two styles different to one another?

In short, filtration involves the use of a filter to capture and trap particles or odours. On the other hand, sterilisation typically refers to simply killing or destroying the particles.

Now, based on that description, you’d be forgiven for believing that sterilisation is the superior option. However, in reality, sterilisation methods are often more limited.

They are ideal for destroying organic particles or microorganisms such as bacteria and viruses. Yet, at the same time, they are typically ineffective against odours, and certain fine particles.

Instead, filtration methods, especially HEPA filters can deal with a vast majority of pollutants. Although, this comes at the price of higher maintenance costs, as the filters need replacing regularly.

What is HEPA filtration?

Now, when it comes to air purification, a term frequently tossed around is HEPA. It stands for High-Efficiency Particulate Air, and it is most easily defined as a standard for purification.

HEPA filters themselves, are typically made of fibreglass paper and are focused on removing contaminants sized 0.3 microns and above.

Therefore, a HEPA filter is essentially assured to be highly capable of removing a variety of pollutants. Additionally, that includes notoriously challenging particles such as PM2.5 and PM10.

HEPA filters also fall into sub-grades ranging from H10 to H14. The higher the number following “H”, the more efficient the filter is.

For example, a HEPA filter grade of H11 indicates 95% efficiency, where a grade of H13 indicates 99.95% efficiency. 

What about ionisation?

Now, out of the seven common purification methods, six are classed as either sterilisation or filtration. However, the seventh instead is known as particle ionisation.

Ionisation can work in a few ways, and some models use particular ions to neutralise bacteria and viruses. The most common application, though, is to release ions, which repel or attract contaminants.

Most ionisation air purifiers produce ions that attract contaminants towards them. Thus reducing their presence in the rest of the environment.

Other, smaller units sometimes release ions that repel contaminants, keeping the nearby space clean.

The former method is, therefore, best in larger spaces, where the latter is best suited to offices or more public spaces.

As with sterilisation, ionisation doesn’t impact odours and is the least effective at permanently reducing pollutant levels. However, it is certainly still a perfectly viable option, and will likely only improve with time.

Which purification method is best?

Ultimately, no single purification method can categorically be the best, as most specialise with different contaminant types. In reality, a combination of multiple will always be far superior to just one alone.

However, if you have to choose, an air purifier that uses HEPA particle filtration is best in most cases. As previously mentioned, HEPA filters target a vast majority of common contaminants and provide a lot of protection.

Alternative methods, such as heat or plasma sterilisation, can also be very effective. Certain heat sterilisation technologies, such as those used by Airfree, can even compete closely with HEPA filters in terms of efficacy.

Although, if you want the best results, a combination of HEPA and carbon filtration is ideal. Even better if they are then paired with a form of heat, UV or plasma sterilisation too.

Overall, the more purification methods in use, the better the quality of the air will be.