ePM1, ePM2.5 and ePM10: Which ISO 16890 Class Suits Your Building?

Choosing an ISO 16890 filter class is not just about selecting the finest filter available. The right choice depends on what is in the air, who uses the building, and what your HVAC system can handle without creating unnecessary resistance.

For facility managers, mechanical contractors and industrial buyers, the key question is simple: which class gives you the air cleaning you need while still fitting the equipment, maintenance plan and site conditions?

What ISO 16890 classes mean in practice

ISO 16890 groups air filters by how well they capture airborne particles in three broad size ranges: ePM1, ePM2.5 and ePM10. In practical terms, the class you choose should reflect the type of dust you are trying to control.

• •ePM1 is used where finer particles are the main concern.
• •ePM2.5 suits applications that need a balance between finer particle capture and manageable airflow resistance.
• •ePM10 is generally selected where the load is mainly coarse dust, lint, fibres or larger outdoor particles.

These classes do not directly convert from MERV, EN 779 or older naming systems. If your building still uses G3, G4 or F5-F9 language, that may help you understand the existing setup, but the best replacement should be selected against the actual duty, not by a simple one-to-one conversion.

Match the filter class to the dust source

Start by identifying where the dust is coming from. A filter that works well for one site may be too restrictive or too coarse for another.

When ePM10 may be enough

ePM10 is often considered where the air stream carries larger particles and visible dust rather than fine airborne contamination. Examples can include:

• •warehouses with general dust and packaging debris
• •loading areas with frequent door openings
• •some industrial or service spaces where coarse debris is the main issue
• •pre-filtration stages before finer filters downstream

If the site has a lot of lint, fibrous material or outdoor dust entering the system, ePM10 can be a practical starting point, especially where the HVAC plant is not designed for higher resistance.

When ePM2.5 is a sensible middle ground

ePM2.5 suits many commercial buildings because it can offer a better balance between air cleanliness and system pressure drop than finer-grade options. It may be appropriate for:

• •offices and retail tenancies
• •education facilities
• •healthcare-adjacent spaces that are not subject to specialised filtration requirements
• •mixed-use buildings with moderate occupant density

If the building sits near traffic, construction activity or other sources of finer dust, ePM2.5 may be a better fit than ePM10.

When ePM1 is the better option

ePM1 is generally chosen when finer particle capture is the priority. That can include:

• •buildings with higher occupancy and recirculated air
• •spaces where indoor cleanliness expectations are higher
• •HVAC systems with staged filtration and adequate fan capacity
• •applications where downstream equipment needs better protection from finer dust

If you are dealing with very fine airborne dust, a stricter filtration stage may be worth considering, but only if the system can maintain acceptable airflow and the maintenance plan supports it.

Occupancy should shape the decision

The number of people in a building affects how hard the ventilation system works and how quickly filters load up with dust and debris. More occupants usually means more indoor particle generation from movement, clothing fibres, paper dust and general activity.

For a lightly occupied building, a coarser class may be enough if the outside air is relatively clean and the internal dust load is modest. In busier areas, finer filtration is often more appropriate, particularly where the building is operated for longer hours or has variable occupancy patterns.

It also helps to think about the space itself:

• •Open-plan offices may benefit from finer filtration if the HVAC system can support it.
• •Schools and training centres often need a practical balance because occupancy changes through the day.
• •Industrial spaces may need a tougher pre-filter arrangement to handle coarse loading before finer stages do the finishing work.
• •Retail and hospitality areas can need closer attention to odour, dust and appearance, depending on the tenancy and air distribution.

If people with health concerns are involved, discuss their needs with an appropriate medical professional rather than relying on filtration alone.

HVAC constraints often decide the final answer

Even if a finer class looks attractive on paper, the HVAC system still has to move air through it. That is where many projects succeed or fail.

A filter with too much resistance for the fan and duct system can lead to poor airflow, unbalanced spaces and maintenance headaches. Before changing class, check:

• •available fan capacity
• •filter face area and housing size
• •existing pressure drop across the current arrangement
• •whether the system uses a single stage or pre-filter plus final filter arrangement
• •space for deeper or larger filters

If the system has limited margin, a stepped filtration approach can work well. For example, a coarser pre-filter can take the heavier dust load, with a finer final filter downstream. That can help protect the final stage and make servicing more manageable, subject to the equipment design.

Pressure drop matters

The best way to judge service timing is by monitoring pressure drop where gauges are fitted. Inspection frequency will depend on the system, the site conditions and the dust load, so follow the filter and equipment manufacturer instructions rather than using a fixed calendar schedule.

If a building is prone to seasonal dust, nearby construction, or changing occupancy, the maintenance plan should reflect that reality. For help with ongoing maintenance, see filter servicing or commercial filter servicing.

Don’t ignore the rest of the filter system

Selecting the right ISO 16890 class is only one part of the job. The filter frame, media depth, fitment and seal are all important.

A good filter choice can still underperform if:

• •the filter does not fit correctly in the holding frame
• •air bypasses the media due to poor sealing
• •the system has not been measured properly before ordering replacements
• •a coarse filter is used where a finer second stage is needed

If you are replacing existing filters, it is worth confirming the exact dimensions before ordering. Our guide on how to measure an air filter can help avoid sizing mistakes.

Some filters are designed to be washable - check the product instructions before assuming a unit can be reused. Where replacement is the right path, custom sizing may be the simplest option for older plant or non-standard housings. See custom air filters if you need a made-to-order solution.

Where standards fit into the decision

For occupied buildings, ventilation requirements should be considered alongside the relevant project brief and site conditions. AS 1668.2:2024 is often part of that conversation, but the final requirement should be confirmed with the mechanical services engineer or building owner.

If you are comparing ISO 16890 classes with older EN 779 terms or with MERV, keep in mind that these systems measure and report performance differently. The safest approach is to look at the actual dust profile, the fan capability and the intended use of the space rather than relying on a conversion chart.

For some projects, HEPA is discussed as a separate category entirely. If that comes up, note that H13 is at least 99.95% efficient and H14 is at least 99.995% efficient at the most penetrating particle size under EN 1822. Those grades are only suitable where the application genuinely calls for them.

Choosing the right class for your site

A practical selection process usually looks like this:

• •identify the main dust type: coarse debris, mixed dust or fine airborne particles
• •assess occupancy and how much indoor particle load the space creates
• •check the HVAC system’s resistance margin and filter housing size
• •decide whether a single-stage or staged approach makes more sense
• •confirm the maintenance plan and inspection method

If you are unsure, start with the building’s dust source and system limits, then work backwards to the filter class. In many cases, the right answer is not the highest-rated filter, but the one that fits the application and can be maintained properly.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, established in 2009. If you need help selecting the right ISO 16890 class, we can supply standard options or make the right filters for your system.

Call 07 3800 3448 or request a quote. You can also explore our products or contact us for direct assistance.