Reading a Filter Datasheet Against AS 1668.2:2024 Requirements

When a filter is nominated on a set of drawings, it is worth checking more than the nominal size. The datasheet should make sense against the building’s ventilation intent, the project specifications and the air handling unit’s operating limits before anything is ordered.

For mechanical contractors and engineers, the key questions are straightforward: does the filter rating suit the required indoor air quality intent, will the pressure drop fit the fan duty, and will the selected product physically fit and seal in the frame or housing? That is the sort of check that can avoid rework later.

Start with the project documents, not the datasheet

The first step is to read the filter schedule alongside the mechanical specification, the drawings and any room or system notes. A datasheet is useful, but it only tells you what a product is capable of under stated test conditions. It does not, by itself, tell you whether the product is the right choice for the system.

Look for the following in the project documentation:

• •the supply air and return air strategy for the space
• •whether the system is for general ventilation, higher filtration, or a process area with specific requirements
• •any stated particle capture level, filter class or preferred standard
• •the allowable initial and final pressure drop range for the plant
• •frame type, access constraints and installation orientation
• •whether the filter is for a pre-filter, final filter or a specialist application

If the documents are not clear, confirm the site requirements with the mechanical services engineer or building owner before you commit to a product.

Match the rating to the ventilation intent

AS 1668.2:2024 sets the ventilation framework, but the exact filter selection still depends on the project brief and the system design intent. A higher rated filter is not automatically the correct answer if the plant cannot handle the extra resistance or if the application calls for a different balance of filtration stages.

When you review the datasheet, check what rating system is being used and whether that matches the specification language. In Australia, you may still see older EN 779 references such as G3, G4 or F5 to F9, while ISO 16890 is now widely used on newer products. These systems do not convert directly, so avoid assuming one class is equivalent to another without checking the actual test data and the specified basis.

If the schedule refers to a particular standard or class, confirm that the product datasheet states the same basis rather than relying on a general description such as “good dust holding” or “high efficiency”. A meaningful comparison needs the actual rating method, test conditions and dust classification.

For HEPA or specialist filtration

If the project calls for HEPA filtration, check that the datasheet states the EN 1822 efficiency at the most penetrating particle size. H13 is at least 99.95% and H14 is at least 99.995% at MPPS.

For specialist applications, also check:

• •the filter leakage or scan test information where applicable
• •gasket type and frame sealing method
• •installation direction and access for safe change-out
• •whether the filter is meant for terminal use or as part of a staged system

Do not treat a high efficiency figure alone as proof of suitability. The whole assembly matters, not just the media rating.

Check pressure drop against the fan and the system

Pressure drop is one of the most important figures on a filter datasheet, because it affects how the system actually performs in the field. A filter may meet the rating requirement but still create more resistance than the fan, controls or plant arrangement can comfortably manage.

When comparing a proposed filter, check:

• •the initial pressure drop at the stated airflow
• •the recommended airflow range for the product
• •the final resistance or terminal pressure drop used for replacement planning
• •whether the pressure drop is for a clean filter or a loaded condition
• •whether the data is per panel, per module or per assembled bank

The airflow used on the datasheet should align with the project airflow. A pressure drop shown at a different flow rate can look acceptable on paper while telling you very little about the actual operating point. If the system is already tight on fan margin, even a small increase in resistance can matter.

Also check whether the fan selection, motor allowance and control strategy can tolerate a filter that loads more quickly than expected for the site conditions. Dusty or dirty environments may require closer attention to resistance growth, but the inspection frequency still depends on the system, site conditions and dust load.

Confirm the physical details, not just the rating

A filter can look right on a schedule and still fail the practical fit check. Before ordering, confirm the dimensions, seal arrangement and frame style against the housing or filter rack.

Useful points to verify include:

• •nominal and actual dimensions
• •depth, flange and lip details
• •gasket position and compression requirements
• •whether the product is rigid, pleated, bag, panel or cartridge style
• •orientation marks and airflow direction
• •access clearances for removal and replacement

If you are measuring a replacement filter, use the existing unit and the housing opening carefully rather than relying on memory. If needed, how to measure an air filter is a practical starting point before you request a replacement or custom size.

For non-standard openings, unusual housings or retrofits, a custom air filters option may be the better path than trying to force a near-match into a frame that was not designed for it.

Read the notes on media, construction and maintenance

The front page of a datasheet rarely tells the full story. Construction notes can affect suitability as much as the rating does.

Look for information on:

• •media type and whether it is synthetic, glass fibre or another construction
• •frame material and corrosion resistance for the site
• •separator or pleat spacing details
• •sealant type and temperature limits if relevant
• •whether the product is disposable or serviceable
• •whether some filters are designed to be washable - check the product instructions

If a washable product is being considered, do not assume all similar-looking filters can be cleaned and reused. The product instructions control that point.

For systems where ongoing attention matters, filter servicing or commercial filter servicing can help keep the change-out process aligned with the equipment manufacturer instructions and the site’s maintenance approach.

Build the final check around the system, not the brochure

A good filter selection process is less about picking the highest number on a datasheet and more about matching the whole assembly to the ventilation design. The best check is a simple one:

• •does the rating match the specified filtration intent?
• •does the pressure drop suit the fan and operating airflow?
• •does the size, seal and frame suit the housing?
• •does the product information align with the project documentation?
• •has the mechanical services engineer or building owner confirmed any site-specific requirements?

If any of those answers is uncertain, pause before ordering. A quick review at this stage is usually easier than dealing with an installation that does not fit the intent on site.

Need the right filter for the job?

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, established 2009. We can help supply or make the right filter for the application, whether you need a standard product or a custom fit.

Call 07 3800 3448 or request a quote. You can also contact us if you want to talk through the datasheet, the airflow requirements or the housing details before you order.