What is a HEPA filter, anyway?

Many high-end air purifiers boast the acronym HEPA in their marketing materials. But why should we be looking out for this labelling in the first place? And what does it mean? In short, it’s a sign of quality and efficacy. HEPA stands for High-Efficiency Particulate Air, which described filters that can capture at least 99.97% of particles above 0.3 micrometres. Although this standard wasn’t established until the 1980s, HEPA filters were invented in the Second World War by American nuclear physicists.

How do HEPA filters work?

Modern HEPA filters are made of glass fibres knitted together into a web-like structure. When particles enter this web, they’re captured via one of four techniques. These are:

  • Direct Impact: Where large particles, like dust, mould and pollen collide with the fibre and stick to it.
  • Sieving: The particles become trapped in the filter in the same manner as rice in a kitchen sieve. 
  • Interception: The airflow reroutes around the fibre, but inertia carries the particles on the same course, sticking to the mesh. 
  • Diffusion: Ultrafine particles move more erratically in the atmosphere, making it more likely they’ll stick to the fibres.

The result is fresh, filtered air, free of contaminants like mould, pollen, bacteria, and viruses. This makes the air quality in the space far higher.

What’s the difference between HEPA-13 and HEPA-14?

In short, 0.025%. A HEPA-13 filter – which is the filter used on most consumer models – traps 99.97% of particles above 0.3 µm. Meanwhile, HEPA-14 filters are 0.025% more efficient, capturing 99.995% of particles. You may think this seems negligible; and really, it is. However, it is the difference between the air being very, very clean and totally sterile.

When you are selecting an air purifier, it isn’t merely a question of getting the highest possible efficacy rating. You have to be realistic about your needs. Although a HEPA-14 filter will make the air sterile, you have to ask yourself if this is necessary. Filters with HEPA-14 have much higher running costs and are far more expensive to replace. Therefore, you have to ask yourself if you want to keep your office fresh and healthy, or if you’re performing open-heart surgery. In reality, 99.97% efficacy is sufficient 99.97% of the time – anything more is overkill.

A final note – another thing to look out for when shopping for an air purifier is ‘HEPA true’ or ‘true HEPA’. It’s important to be aware that this is a marketing term that covers H10–H12 filters, which only capture 85-99.5% of particles. If you’re looking for a really effective air purifier, this is ‘under kill’, if you will.

Rejuvenair offers HEPA quality

Rejuvenair’s air purifiers are fitted with high-quality H-13 HEPA filters to keep the air in workplaces and public buildings fresh and healthy. Combined with UVC purifying technology, Rejuvenair units kill 99.9% of contaminants in rooms up to 60m2. Plus, this efficacy is balanced with appropriacy, ensuring that the unit is cost-effective as it is powerful. 

Our engineers maintain this level of service by monitoring the condition of the filter remotely, so you can organise replacements or repairs in a timely manner from the built-in app. All this, and Rejuvenair pride ourselves on offering one of the most environmentally friendly options available.