Comparing Filter Options for Strata Common Areas With Frequent Door Openings

Strata lobbies and corridors with busy entry doors face a particular challenge: each opening can let in outdoor air, dust and odours while also disrupting the balance of conditioned air. That means the best filter is not always the one with the highest rating, but the one that suits the system, the airflow available and the amount of dust the space actually sees.

For strata managers, the goal is to choose a filter that protects the air handling equipment, supports comfortable common areas and can be maintained without creating avoidable pressure drop. The right choice depends on the building’s ventilation design, the door traffic pattern and the maintenance approach agreed with the mechanical services engineer or building owner.

Why frequent door openings change the filter decision

When entry doors open often, common areas can experience short bursts of outside air ingress. In a lobby, that may bring in street dust, pollen, lint, vehicle emissions and general fine particles. In a corridor, the effect is often less dramatic than at the main entry, but repeated door use can still alter the way the HVAC system performs.

This matters because the air filter is doing two jobs at once:

• •capturing airborne particles before they enter the fan coil, air handling unit or supply system
• •managing airflow resistance so the system can continue moving air properly

If a filter is too restrictive for the available fan capacity, the system may struggle to deliver the intended airflow. If it is too coarse, more particles may pass through and be deposited deeper in the system or on internal surfaces.

In practical terms, the best option is often a balanced filter grade that matches the contamination load and the equipment’s operating limits rather than simply choosing the finest filter available.

Start with the system, not just the filter rating

Before comparing products, confirm what the system was designed to take. In strata buildings, the existing filter frame, the fan strength, the available filter depth and the service access all affect which options are realistic.

Useful checks include:

• •the filter dimensions and installation depth currently in use
• •the type of system serving the lobby or corridor, such as a packaged unit, fan coil or air handling unit
• •whether the building has differential pressure gauges or other monitoring points
• •the manufacturer’s recommendations for allowable airflow resistance
• •whether the installation aligns with the intent of AS 1668.2:2024, noting that site requirements should be confirmed with the mechanical services engineer or building owner

If you are unsure about sizing or fit, how to measure an air filter is a good starting point. Getting the dimensions right is essential, because a poor fit can allow air to bypass the filter media altogether.

Comparing common filter options for strata common areas

Coarser pre-filters for heavy ingress

In some lobby systems, a coarser pre-filter is used to catch larger dust and lint before air reaches a finer final filter. This can be a practical approach where there is frequent door opening and visible loading from street air.

A coarser filter may be suitable when:

• •the system has limited fan capacity
• •the main concern is protecting equipment from heavier debris
• •the building wants to reduce how quickly the finer filter loads up

The trade-off is that coarse media will not capture as much fine particulate matter as a finer filter. It is often used as part of a staged setup rather than as the only filter in the system.

Medium filters for a balanced approach

For many strata common areas, a medium-efficiency filter is the practical middle ground. It offers better particle capture than a coarse pre-filter while usually remaining manageable for systems that are not designed for very high resistance.

These filters are often considered when the building has:

• •regular foot traffic through the main entrance
• •moderate dust from outside air ingress
• •a need to maintain airflow without overloading the fan

Where the system is running continuously or serving a prominent shared space, a medium filter can be a sensible compromise between capture and airflow.

Finer filters where the system can handle the load

If the HVAC equipment has enough capacity and the building wants more robust particle capture in the common area supply air, a finer filter may be appropriate. In Australia, people still often refer to the older EN 779 classes such as G3, G4 and F5 to F9, even though ISO 16890 is now the current rating framework.

That said, ratings do not convert directly from one standard to another, so it is better to compare the actual product data rather than rely on a rough equivalent. A finer filter can help capture smaller particles, but it also creates more resistance, which may affect airflow if the fan is already working hard.

For systems with clearly defined performance requirements, the final selection should be checked against the equipment design and site conditions.

When a higher-efficiency filter makes sense

A high-efficiency filter is not automatically the right answer for a lobby or corridor, but it can be useful in certain situations. For example, if the system is designed for a deeper filter bank and the common area sees strong outside air ingress, a higher-efficiency product may help improve particle capture before air is delivered back into the space.

If a building is considering HEPA-level filtration, it is important to understand the actual rating and the system implications. Under EN 1822, H13 filters are at least 99.95% efficient at the most penetrating particle size, and H14 filters are at least 99.995% efficient at MPPS. Those filters are typically used where the system design specifically calls for that level of performance, because they can impose substantial airflow resistance.

For most strata common areas, the question is not whether HEPA is “better”, but whether the system can support it without compromising airflow or maintenance practicality.

Maintenance matters as much as the media choice

A filter choice only works if it can be maintained properly. In a lobby with frequent door openings, the dust load may rise and fall with weather, construction nearby, traffic patterns and seasonal conditions. That means inspection frequency should be based on the site, not on a fixed calendar.

When assessing a filter program, consider:

• •visual inspection of the filter condition and surrounding housing
• •pressure drop monitoring where gauges are fitted
• •the manufacturer’s instructions for the filter and the equipment
• •whether the building has nearby construction, landscaping or other dust sources
• •whether the filter is in a pre-filter position or a final filter position

Some filters are designed to be washable - check the product instructions. Others are intended to be replaced when they reach their service limit. Using the right maintenance method matters, because the wrong cleaning approach can damage the media or reduce performance.

If you are managing a wider service program, commercial filter servicing can help keep the system on track. For buildings that prefer an ongoing maintenance plan, filter servicing is also worth reviewing.

Practical selection tips for strata managers

When comparing filter options for a busy common area, keep the decision anchored to the building’s actual conditions. The best choice is usually the one that balances airflow, capture and serviceability.

A useful shortlist is:

• •choose a filter that matches the existing frame and available depth
• •consider a staged setup if the system sees heavy outside air ingress
• •avoid selecting a filter solely on rating without checking airflow resistance
• •confirm any special requirements with the mechanical services engineer or building owner
• •monitor the filter after installation and adjust the maintenance approach based on real site conditions

If your lobby or corridor has ongoing dust issues, it may also be worth reviewing whether the current filter arrangement is the right fit for the building’s ventilation setup. In some cases, a custom size or a different media configuration is the cleanest solution. See custom air filters and our products for more options.

Need help choosing the right filter for your building?

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD, and we can help supply or make the right filters for strata common areas with frequent door openings.

Call 07 3800 3448 or request a quote if you would like help matching a filter to your lobby, corridor or other shared space. You can also contact us for practical advice on fit, servicing and product selection.