What does an M5 filter capture, and when is it enough? A practical guide to M5, ePM10, pollen, PM10, M5 vs G4 and F7, airflow and replacement.
An M5 filter is the middle ground between coarse G4 filtration and finer F7 filtration. In residential MVHR and heat-recovery systems, it can be a sensible choice when you want better control of pollen, dust and PM10-range particles without automatically moving to a finer F7 or ePM1 filter.
The key question is not whether M5 is “good” or “bad”, but whether the outdoor air around your home is mainly a PM10 problem or whether fine PM2.5 pollution from traffic, heating or smoke is the bigger concern.
Choose M5 if you are sensitive to pollen, outdoor PM10 pollution is elevated, and fine PM2.5 pollution is not the main problem where you live. Compared with G4, M5 provides much better protection against pollen and PM10-range particles that a coarse filter does not effectively capture. If there is no significant fine-particle pollution from solid-fuel heating, heavy road traffic or industrial emissions, M5 offers a strong balance between useful particle protection, low airflow resistance and practical service life.
M5 is a filter class from the older EN 779 system. It sat in the medium filtration range: finer than G4, but below F7. You will still see M5 in ventilation-unit manuals, replacement-filter catalogues and normal product searches.
The current ISO 16890 system classifies general-ventilation filters by particulate-matter efficiency, using groups such as ISO Coarse, ePM10, ePM2.5 and ePM1. That means an M5 label cannot be converted into one exact ISO percentage.
Reference: Eurovent Recommendation 4/23. ISO 16890 classifies general-ventilation filters by particulate-matter efficiency; see the ISO 16890-1 overview.
M5 is useful because it captures much more of the medium-size particle load than a coarse G4 filter while still sitting below fine F7 filtration. For a homeowner, that makes it most relevant to pollen, outdoor dust, mould spores and PM10-range pollution.
PollenUseful seasonal reduction of larger airborne pollen particles
Mould sporesCan reduce many larger airborne spores entering with outdoor air
Dust and sandOutdoor dust, road dust, soil and other larger particles
PM10 particlesA meaningful share when the specific filter carries an ePM10 ratingIllustrative photos: Soumalya Mandal, Sandy Millar, Devon Janse van Rensburg and Call Me Fred / Unsplash.
An M5 filter also catches insects, fibres and other larger debris. On the extract-air side it can help keep the heat exchanger and internal surfaces cleaner than a very coarse filter would.
M5 makes the most sense when the outdoor environment is relatively clean and the main reasons for filtration are pollen, dust and occasional PM10 episodes rather than persistent fine-particle pollution.
If local PM2.5 levels are usually low and there is no busy road or combustion source nearby, M5 can be a practical middle option for supply air where the unit allows it.
You do not automatically need F7 just because pollen is a concern. M5 can provide useful pollen reduction, while the exact result still depends on the specific filter and pollen size.
Dry weather, field work, construction dust or wind-blown mineral dust can raise PM10. A tested ePM10 filter is directly relevant to this particle range.
If your local air-quality data regularly shows elevated PM2.5, M5 is no longer the strong choice for incoming air. Fine combustion particles are common around heavy traffic, dense urban areas, winter wood or solid-fuel heating and smoke events.
Busy trafficFine traffic-related particulate pollution can make F7 more appropriate
Heating seasonWood and solid-fuel combustion can raise PM2.5 substantially
Smog or inversionsFine particles can remain trapped even away from a main road
Wildfire smokeSmoke is dominated by fine particles that call for finer filtration
Do not judge only by “city” or “countryside”. Check local PM2.5 and PM10 data. WHO notes that PM2.5 can penetrate deep into the lungs and enter the bloodstream, which is why persistent fine-particle pollution deserves more attention than larger dust alone. WHO: air-pollution health impacts.
There is no one universal position. Some ventilation units use M5 on both air paths; others pair an F7 supply-air filter with an M5 extract-air filter. Always follow the model diagram and the airflow arrows on the filters.
Some Vortice units use an M5 + M5 arrangement. This gives medium particle filtration on the outdoor-air side while also protecting the unit from dust carried by extracted indoor air.
Other units use a mixed F7 + M5 set. The finer filter handles incoming outdoor air while M5 is used on the other side for better component protection than a coarse filter. This arrangement appears in products such as Aerauliqa QR280 and bluMartin freeAir 100.
The three classes solve different problems. The best filter is the one that matches the air quality around the home and the ventilation unit’s permitted resistance.
| Filter | Main role | What it handles well | Fine PM2.5 / PM1 | Typical resistance |
|---|---|---|---|---|
| G4 / ISO Coarse | Basic unit protection | Large dust, lint, insects, coarse debris | Limited | Usually lowest |
| M5 / ePM10 range | Intermediate filtration | Pollen, dust, mould spores, meaningful PM10 fraction | Limited to moderate depending on the exact filter | Usually between G4 and F7 |
| F7 / often ePM1 or ePM2.5 range | Fine supply-air filtration | Pollen plus much more PM2.5 and PM1 | Much stronger | Usually highest of the three |
M5 is a real step up from G4 for incoming-air quality. It captures a substantially larger share of medium-size particles and is much more relevant when pollen and PM10 matter. The trade-off is higher airflow resistance than a typical coarse filter.
F7 provides much stronger filtration of fine PM2.5 and PM1 particles. That is useful around traffic, combustion and winter smog, but the finer medium often adds more resistance. If your air is generally clean and your main problem is pollen or PM10, M5 can be the more balanced choice.
Often yes, but not as a universal rule. A less fine filter commonly creates less resistance than a denser fine-particle filter of similar size, which can make it easier for the ventilation unit to maintain airflow. Eurovent also notes that filter resistance directly affects ventilation energy use.
That does not mean every M5 automatically saves energy or lasts longer than every F7. The real pressure drop depends on the filter media, pleat area, dimensions, airflow and how quickly dirt loads the filter.
If the filter creates less pressure drop, the fan has less work to do to maintain the same airflow.
A well-designed pleated F7 can sometimes outperform a poorly designed M5 on pressure drop. The filter material matters too. ZenAero uses modern EU-made low-resistance filter media in both its F7 and M5 filters to balance particle filtration with airflow performance. Compare the complete filter design and tested data where available, not the class label alone.
As dust accumulates, resistance rises. A clean higher-grade filter can perform better than a neglected lower-grade one.
Rooms feel stuffy, especially in the morning, or the system no longer seems to move the same amount of air.
The fans may run harder as filter resistance rises. A change in normal system noise is worth checking.
Heavy dust, darkened media or a unit filter warning are direct reasons to inspect and replace it.
These ZenAero compatible products contain M5 / ePM10 60% filtration either as an M5 + M5 set or paired with an F7 supply-air filter. Choose by the exact ventilation-unit model and dimensions.
Vortice HRI 200, Vortice VORT AVEL, Aerauliqa QR280 and bluMartin freeAir 100.
Available in selected options
Price range: 25.45 € through 86.45 €
Available in selected options
Price range: 26.95 € through 88.45 €
Available in selected options
Price range: 22.95 € through 77.95 €
Available in selected options
Price range: 15.95 € through 47.45 €Prices and availability in the product cards update from the live catalogue. Browse all ventilation-unit filters by make and model.
Send the MVHR model, a photo of the old label and the dimensions. We will check the correct filter set and class.
