What a Mechanical Contractor Should Check on a Filter Certificate Before Ordering

When you are reordering filters for a plant room, office fitout or industrial site, the certificate or test report should tell you more than just the part name. The details on that document can confirm whether the replacement will fit, seal and perform the way the system expects, especially when you are matching an existing order or substituting a product that is no longer available.

A quick check before ordering can save time on site and reduce the risk of getting a filter that looks right on paper but is wrong in the cabinet. Use the checklist below to compare the certificate with the actual filter, the equipment schedule and any site-specific requirements.

Start with the identification details

The first thing to check is whether the certificate clearly identifies the exact product you are ordering.

Look for:

• •Manufacturer or supplier name
• •Product code, model number or part reference
• •Filter type description, such as panel, pleated, bag, compact, carbon or HEPA
• •Any variant details, such as depth, media type or sealing method
• •Batch or production reference, if supplied

If the certificate only gives a broad description, that may be fine for a general reference, but it is not enough if you need an exact repeat order. The product code should match the filter in the system, not just a similar-looking alternative.

If the original filter was a special size or built to suit a particular cabinet, check whether the document refers to a standard item or a custom air filters order.

Confirm the dimensions and fit data

Size is one of the most common reasons a replacement filter is rejected on site. The certificate should show the dimensions in a way that matches how the filter is measured and installed.

Check for:

• •Nominal size and actual size
• •Length, width and depth, or diameter for round filters
• •Insert depth or frame depth where relevant
• •Gasket or seal dimensions, if applicable
• •Tolerance notes, if the product is made to a specific fit

Do not assume a nominal size is enough. In many applications, the actual dimensions are what matter for clearance and sealing. If you are unsure how the size should be taken, compare the filter with the site method or use how to measure an air filter as a guide.

Also check whether the frame or holding system needs a specific style of edge, lip, flange or seal face. A filter can be the right size but still not sit correctly in the rack or housing.

Check the performance rating carefully

A certificate should state the filter’s rating in the same system used for the original selection or the equipment schedule. This is important because filter rating systems do not convert directly from one another.

Look for the rating standard used, such as:

• •MERV
• •EN 779 classes such as G3, G4 or F5 to F9, where still specified on older documents
• •ISO 16890 ratings
• •HEPA classification, where relevant

If the certificate refers to HEPA, make sure the class is clearly shown. H13 is at least 99.95% efficiency at the most penetrating particle size under EN 1822, and H14 is at least 99.995% under the same standard. That level of detail matters when the filter is being used in applications that need a defined high-efficiency classification.

For general HVAC work, do not try to translate one rating system into another by guesswork. Instead, match the certificate to the original specification, the equipment requirements and, where needed, the mechanical services engineer or building owner.

Review airflow, resistance and operating data

A filter may be the correct physical size but still be unsuitable if the airflow or pressure characteristics are wrong for the system.

On the certificate or report, check for:

• •Rated airflow range
• •Initial resistance or pressure drop
• •Final resistance or recommended change-out resistance, if listed
• •Face velocity limits, where applicable
• •Maximum operating temperature, if relevant to the site
• •Any notes about installation orientation or load direction

These figures help you compare the replacement with the existing unit and the fan or air handling system. If the new filter has a significantly different resistance profile, it may affect the system balance and the way the pressure drop behaves as dust loads build up.

Where gauges or monitoring devices are fitted, make sure the site team knows what readings they should watch. Inspection frequency depends on the system, site conditions and dust load, and you should follow the filter and equipment manufacturer instructions.

Confirm the media and construction details

The certificate should also tell you what the filter is made from and how it is built. That matters when the system sees heat, humidity, dust, odour or regular maintenance handling.

Look for details such as:

• •Filter media type, such as synthetic, fibreglass, carbon or other media
• •Frame material, such as cardboard, galvanised steel, aluminium or plastic
• •Separator or pleat support type
• •Sealant or potting compound, where used
• •Pleat count or media area, if listed
• •Reinforcement or mesh support, if relevant

These details can affect how the filter behaves in service and whether it suits the environment. For example, a filter for a commercial tenancy may need a different construction from one used in a dusty workshop or a process area.

Some filters are designed to be washable - check the product instructions before assuming a filter can be cleaned and reused. If the document does not clearly say the product is washable, treat it as a non-washable filter until the supplier confirms otherwise.

Look for installation and compliance notes

A certificate should also be checked for any notes that affect installation or system acceptance.

Useful items include:

• •Recommended airflow direction
• •Installation orientation
• •Seal requirements or gasket notes
• •Compatibility notes for specific housings or holding frames
• •Fire, temperature or material notes, if stated
• •Any reference to site-specific design criteria

If the project is tied to building ventilation requirements, confirm the site requirements with the mechanical services engineer or building owner. For ventilation work, AS 1668.2:2024 may be relevant, but the correct selection still depends on the actual project specification and the equipment being maintained.

If the certificate is for a specialist application, ask whether the filter is intended for standard HVAC service, prefiltration, fine filtration or a process duty. That helps prevent ordering a product that looks suitable but does not match the intended use.

When the certificate is not enough

Sometimes the document on hand is incomplete, outdated or written for another version of the filter. In that case, do not rely on assumptions.

You should verify the order if:

• •The part code has changed
• •The old filter was modified on site
• •The cabinet has been altered
• •The original supplier documentation is missing key data
• •A substitute product is being proposed
• •The filter is used in a critical or tight-fit installation

If you need to compare options across our range, see our products or industries we supply for the types of systems we regularly support. If the filter is no longer standard, a made-to-order solution may be the best path.

A quick checklist before you place the order

Before sending the order through, compare the certificate against the installed filter and the equipment schedule. Make sure you have:

• •The exact product code
• •The correct actual dimensions
• •The right rating system and class
• •Matching airflow and pressure data
• •Media and frame details that suit the application
• •Installation notes that fit the cabinet and site conditions

If any of those items are unclear, it is worth pausing and confirming them first. A few extra minutes on the paperwork can prevent an avoidable call-back.

Need a replacement filter checked or made to suit?

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD. If you want help matching a certificate to the right filter, or you need a substitute or custom order checked before production, call 07 3800 3448 or request a quote.

You can also contact us if you want to talk through an existing certificate, a site measurement or a repeat order that needs confirming before it goes in.