ISO 16890 for Office Buildings: Choosing ePM1 vs ePM2.5 for Tenant Comfort

Office HVAC systems in Brisbane have to deal with dust from traffic, construction, occupants, and outdoor air intake conditions that change through the year. When it is time to choose a filter under ISO 16890, the decision often comes down to whether ePM1 or ePM2.5 is the better fit for tenant comfort, airflow and system pressure in the building.

For office managers and mechanical contractors, the right answer is not always the highest filtration grade. It is the filter that suits the system design, the dust load, and the building owner’s expectations for indoor conditions and maintenance.

What ISO 16890 means in an office building

ISO 16890 classifies air filters by the size of the particles they capture, using categories such as ePM1, ePM2.5 and ePM10. In simple terms, the rating tells you what portion of airborne particulate matter the filter is intended to capture at different particle sizes.

For offices, the most relevant classes are usually:

• •ePM1 for finer particles that can affect indoor dust levels and overall air cleanliness
• •ePM2.5 for fine particles while generally placing less demand on the fan and filter bank than a tighter filter choice
• •ePM10 when the aim is mainly coarse dust control at a lower resistance level

ISO 16890 replaced older rating systems, but in Australia you may still hear people talk about G3, G4 or F5 to F9 filters. Those older EN 779 classes do not convert directly to ISO 16890 classes, so it is better to select based on the actual performance data for the filter you are considering.

For buildings that must also align with ventilation design expectations, site requirements should be confirmed with the mechanical services engineer or building owner, and AS 1668.2:2024 may be relevant to the overall ventilation approach.

ePM1 vs ePM2.5: what changes in practice

The main difference between ePM1 and ePM2.5 is how much fine particulate matter the filter is designed to capture and how that choice affects resistance to airflow.

When ePM1 makes sense

ePM1 is often considered where the building has a higher expectation for fine dust control, or where occupants are sensitive to visible dust accumulation on desks, furniture and return air grilles.

It may be the better option when:

• •the office has a higher level of outdoor air exposure near busy roads or active construction
• •tenant presentation is important, especially in reception areas, boardrooms and premium office tenancies
• •the HVAC system has been designed with enough fan capacity to handle the added resistance
• •the maintenance team can monitor pressure drop and replace filters when the system indicates it is time

When ePM2.5 is a practical choice

ePM2.5 can be a balanced option where the building wants stronger fine dust capture than a coarse filter, but the HVAC system is sensitive to pressure rise.

It may suit situations such as:

• •older office plant with limited spare fan capacity
• •systems that are already operating close to their design pressure
• •multi-tenant buildings where keeping airflow steady is a priority
• •sites where the dust load is moderate rather than heavy

In many Brisbane office setups, ePM2.5 is a sensible middle ground between dust control and airflow management. It can improve air cleanliness without imposing as much resistance as a tighter filtration choice might in the same housing.

How airflow and pressure drop affect the decision

A filter is not just a dust capture device. It also adds resistance to the air moving through the HVAC system. If the resistance becomes too high for the fan and ductwork arrangement, airflow can drop and the system may become harder to balance.

That is why the best ISO 16890 class is the one that suits both the indoor environment and the equipment.

Points to review before upgrading filtration

• •Fan capacity: check whether the existing fan can handle the planned filter resistance
• •Filter frame depth and face velocity: the same ISO class can behave differently depending on filter size and loading
• •Return air conditions: higher dust levels can raise pressure drop more quickly
• •BMS or differential pressure gauges: use the readings where fitted rather than guessing by appearance alone
• •Access and maintenance space: a filter that is difficult to inspect often leads to delayed servicing

If a building has nuisance dust, poor intake location, or ongoing tenant complaints about visible dust, it can be tempting to choose the tightest filter available. But if that creates excess resistance, the system may no longer deliver the airflow it was designed to provide. In those cases, a carefully chosen ePM2.5 filter may outperform an over-specified ePM1 option in day-to-day operation.

Practical guidance for Brisbane office HVAC systems

Brisbane office buildings often face a mix of outdoor dust, humidity, and variable occupant loads. That means filtration decisions should be based on the actual site conditions rather than a one-size-fits-all rule.

A useful way to decide is to ask three questions:

• •What dust problem are we trying to solve?
• •What does the HVAC system tolerate without airflow issues?
• •What level of maintenance monitoring is realistic for this site?

If the main issue is fine dust on internal surfaces and the system can support it, ePM1 may be worth considering. If the main goal is to improve indoor cleanliness while protecting airflow and avoiding an early rise in pressure drop, ePM2.5 is often the more practical starting point.

For some buildings, a staged approach makes sense. Coarser pre-filters can take the heavier dust load first, with the final filter selected to suit the system and the tenant expectations. That can help extend the useful life of the final filter stage, but the exact arrangement should always suit the equipment and the filter manufacturer’s instructions.

Maintenance planning matters as much as rating

Even a well-chosen filter will not perform well if it is left in service beyond its useful condition. Inspection frequency depends on the system, site conditions and dust load, so there is no fixed replacement schedule that suits every office.

A good maintenance plan should include:

• •regular visual checks where access is available
• •pressure drop monitoring where gauges are fitted
• •replacement or servicing in line with the filter and equipment manufacturer instructions
• •attention to damaged seals, bypass leakage and poor fitment
• •review after any nearby construction, tenancy change or intake alteration

Some filters are designed to be washable - check the product instructions before deciding whether that is suitable for a particular application.

If you are unsure about fitment or dimensions, it helps to measure the existing filter accurately before ordering. Our guide on how to measure an air filter can help with that process.

Choosing the right option for the building, not just the brochure

The best filter choice for an office building is the one that balances particulate capture, airflow and pressure rise in the actual HVAC system. In some Brisbane offices, that will be ePM1. In others, ePM2.5 will be the more stable and practical option.

If you are comparing options for a new fitout, base building upgrade or routine filter change, consider the filter housing, fan capacity, tenant requirements and maintenance access together. If the building owner has a preferred maintenance program, keep that in mind as well.

For a broader look at what we supply, see our products and commercial filter servicing.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD, established 2009. We can help you choose or make the right filters for your office HVAC system, including standard and custom sizes.

Call 07 3800 3448 or request a quote. You can also contact us if you want help matching a filter to an existing frame, plant room setup or servicing plan.