The seven-layer air purifier filtration stack, explained

Key takeaways

• The stack starts with physical filtration stages that remove larger particles before finer filtration has to work as hard.
• H13 medical-grade HEPA sits at the core of the stack, capturing at least 99.95 percent of particles down to 0.1 micron.
• UV-C sterilisation and anion release add active elimination on top of HEPA's trapping, which is the key difference from a HEPA-only unit.
• Not every product in AIRE's range uses all seven layers, since compact and personal units are built around a smaller stage count for their size.

Layer one: aluminium pre-filter for larger particles

The first stage in the stack is a washable aluminium pre-filter, which catches larger particles like dust, hair and lint before air moves any further into the unit. This isn't where the meaningful filtration happens, but it matters because it protects the finer stages downstream from clogging prematurely with material that didn't need advanced filtration to catch in the first place.

Because it's washable rather than disposable, the pre-filter is also the stage a user maintains most often, typically rinsed periodically to keep airflow through the rest of the unit consistent.

Skipping this maintenance step doesn't stop the unit from running, but it does mean the finer stages further down the stack start working harder than they need to, which can shorten their useful life.

Layer two and three: cold catalyst and activated carbon

After the pre-filter, air passes through a cold catalyst stage and an activated carbon layer. These two work on gases and odours rather than particles: the cold catalyst helps break down certain volatile compounds, while activated carbon adsorbs odour molecules and some airborne chemicals, which is why these stages matter for renovation VOC concerns, cooking smells or clinical disinfectant odours.

Particle filtration alone doesn't address smell, so these gas-phase stages are what actually reduce the odour side of an air quality complaint, separate from the particle-capture work happening elsewhere in the stack.

This is worth knowing if a complaint is specifically about smell rather than dust or allergens, since it points to these two stages rather than the HEPA filter as the part doing the relevant work.

Layer four: the antibacterial layer

The antibacterial layer sits between the gas-phase stages and the HEPA filter, adding a further barrier against microbial growth building up within the filter media itself over time. This matters for any filter stack that runs continuously, since a filter that's constantly capturing biological material needs its own defence against that material multiplying inside the unit.

This stage supports the rest of the stack rather than being the primary line of defence, but it's part of why the overall system is described as more than a HEPA filter alone.

It's a good example of how the seven layers are designed to work together rather than as a simple list, each stage addressing a specific limitation of the stage before it.

Layer five: H13 medical-grade HEPA

H13 sits at the centre of the stack and does the heavy lifting on particle capture, rated to capture at least 99.95 percent of particles down to 0.1 micron. This is the medical, or True HEPA standard, distinct from the ordinary HEPA-type filters in the H10 to H12 range that capture less and aren't an equivalent standard.

It's worth being clear about what HEPA does and doesn't do: it traps particles physically, including viruses and bacteria attached to larger droplets, but trapping is not the same as eliminating. A captured pathogen sitting in a filter is still a live pathogen until something else deals with it, which is where the next stages come in.

All of AIRE's room purifiers use H13 as standard, so this stage is present across the range rather than reserved for a premium tier only.

Layers six and seven: UV-C sterilisation and anion release

The final two stages are where active elimination happens rather than passive trapping. A fully enclosed UV-C lamp targets pathogens with ultraviolet light as air passes through, while anion release adds an additional mechanism working on airborne particles and microorganisms. Together with copper-silver ion sterilisation used in some AIRE units, this is what allows active elimination of over 99.99 percent of airborne pathogens, including E. coli, Staphylococcus albus and Influenza A in testing, within around 60 minutes, compared with a passive HEPA-only unit that can take four hours and 23 minutes or more to reach a similar reduction through decay alone.

This active stage is the core distinction AIRE draws between a medical-grade unit and a general consumer purifier: trapping particles is only half the job, and these final layers are built to finish it.

Next step

See how these layers come together across AIRE's full range on the technology page, or check which model fits your space on the products page.

Frequently asked

What does each of the seven filtration layers do?

The stack runs from a washable aluminium pre-filter for larger particles, through a cold catalyst and activated carbon stage for gases and odours, an antibacterial layer, H13 medical-grade HEPA for fine particle capture, then UV-C sterilisation and anion release for active elimination. Each stage handles a different part of the air quality problem rather than duplicating the same function.

Why does the stack use both HEPA and UV-C together?

HEPA physically traps particles, including pathogens attached to larger droplets, but trapping alone doesn't eliminate what's captured. Adding UV-C sterilisation and ion-based technology allows the system to actively eliminate pathogens rather than leave them sitting live in the filter.

Does every product in the range use all seven layers?

No, the full seven-layer stack applies to AIRE's medical-grade room units such as the Classic 400S and Pro 800S. Compact and personal units, and the automotive range, are built around a smaller stage count suited to their size and use case.