What to Specify for Spray Booth Make-Up Air in Panel Shops

Spray booth make-up air is easy to overlook until finish quality, airflow balance or dust build-up starts causing problems. In panel shops, the make-up air unit does more than bring air back into the building — it helps set the standard for how clean, stable and dependable the spray environment will be.

If you are specifying filters for a spray booth make-up air unit, the main goals are straightforward: supply clean air, keep overspray and shop dust away from sensitive components, and maintain consistent airflow through the booth and surrounding work area.

Start with the air quality the booth actually needs

The first step is to match filtration to the job being done in the shop. A panel shop may have grinding, sanding, body preparation and spray application all happening in the same facility, but the make-up air system should not be treated as a one-size-fits-all setup.

What matters most is the condition of the air entering the booth or the booth supply system. If incoming air carries dust, lint or other airborne particles, those particles can affect finish consistency and create more maintenance on the spray equipment and ductwork.

When specifying filters for make-up air units, consider:

• •The sensitivity of the spray process
• •Whether the unit supplies general workshop air, booth air, or both
• •How much dust is present in the wider workshop
• •Whether the site has nearby outdoor dust sources, traffic or construction activity
• •The space available for pre-filtration and final filtration stages

A staged approach is often the most practical. Coarser filters can be used to remove larger airborne debris first, followed by finer filters where cleaner supply air is needed. This helps protect downstream components and keeps the system easier to manage.

Protect the make-up air unit from overspray and workshop dust

Make-up air systems serving spray booths are exposed to more than just outdoor air. In panel shops, overspray, sanding dust and general workshop contamination can all affect filter loading and airflow.

This is why filter selection should not stop at the intake grille. The full air path needs to be considered, especially where the make-up air unit sits close to spray operations or where recirculated workshop air may be part of the broader ventilation arrangement.

Useful protection measures include:

• •A robust pre-filter stage to catch larger airborne particles before they reach finer filters
• •A final filter stage where cleaner supply air is required for the booth or finishing area
• •Proper filter sealing so air does not bypass the filter media
• •Filter access that supports safe inspection and changeout

Overspray can rapidly load filters if the intake position is poorly chosen. Where possible, locate air intakes away from spray discharge paths, sanding stations and doors that open onto dusty external areas. If that is not possible, the filter arrangement needs to be selected with that contamination in mind.

Some filters are designed to be washable - check the product instructions. In other cases, disposable filters are the better choice because they provide predictable airflow and simpler servicing.

Keep airflow stable, not just clean

A spray booth needs airflow that is steady and predictable. Even if the air is clean, the system still has to move enough of it without large pressure swings that upset booth balance or strain fans.

Filters influence this balance directly. As filters load with dust, resistance rises and airflow can drop. If the filter selection is too restrictive from the start, or if the unit has insufficient filter area, the system may struggle to maintain consistent air delivery.

To help keep airflow stable:

• •Choose filters with enough surface area for the duty
• •Match the filter grade to the actual contamination level, not just the most demanding assumption
• •Check that the fan and motor selection suit the total resistance of the filter bank
• •Use pressure gauges or monitoring points where fitted so loading can be observed
• •Review how filter condition changes after sanding, spraying and general workshop use

If the booth feels harder to balance over time, the cause is often not the spray equipment itself but the condition of the make-up air filters. A filter setup that is too light on pre-filtration may clog quickly. A filter setup that is too restrictive may reduce airflow before the filters are even heavily loaded.

Choose filter stages that suit the site layout

Different panel shops need different make-up air arrangements. Some have compact booth rooms with limited plant space. Others have larger workshops with separate prep areas, spray zones and drying bays. The filter arrangement should suit the physical layout as well as the air quality target.

Common considerations include:

• •Intake filtration for outdoor air entering the make-up air unit
• •Pre-filtration to protect downstream filters and coils
• •Fine filtration where cleaner supply air is required for finishing areas
• •Filter access for safe inspection and replacement
• •Cabinet fit and seal quality to reduce bypass

If the unit also supports cooling or heating coils, filter choice becomes even more important. Dust build-up on coils can affect performance and increase maintenance effort. Good filtration upstream helps protect those components.

For jobs where the booth or make-up air equipment has unusual dimensions, custom air filters may be the simplest way to get the right fit and avoid air bypass around the frame.

Know when standards and site rules need to be checked

AS 1668.2:2024 is relevant when considering ventilation and indoor air management, but the right make-up air setup still depends on the specific site, the booth design and the mechanical services requirements. Confirm site requirements with the mechanical services engineer or building owner before finalising filter selections.

If you are comparing filter types, keep in mind that MERV, EN 779 and ISO 16890 ratings do not convert directly. In Australian projects, you may still hear older EN 779 classes such as G3, G4 and F5 to F9, even though ISO 16890 is now widely referenced. The safest approach is to select based on the actual operating conditions, the equipment specification and the pressure drop the system can support.

If you are unsure what is already installed, it can help to review the current filter size and configuration before ordering replacements. Our guide on how to measure an air filter can help with that.

Plan for servicing, not just installation

A spray booth make-up air system is only as good as its upkeep. Filters should be inspected according to the system, site conditions and dust load, and you should follow the filter and equipment manufacturer instructions. Where gauges are fitted, monitor pressure drop so you can see when the filters are loading.

Good servicing practice includes:

• •Checking seals and frame fit during every inspection
• •Looking for dust tracking around the filter edges
• •Watching for unusual fan noise or reduced airflow
• •Confirming that filters are installed in the correct direction
• •Replacing or cleaning filters only in line with product instructions

For businesses managing more than one unit, filter servicing or commercial filter servicing can help keep maintenance organised.

What to specify before you order

When you are putting together the order for a spray booth make-up air system, gather the details that affect fit and performance:

• •The unit make and model, if known
• •Filter dimensions and frame style
• •The number of stages required
• •The expected dust load in the shop
• •Whether the air is for general makeup or finishing-grade supply
• •Any space limits around the filter bank
• •The current pressure drop reading, where available

If the project is still in design, it helps to talk through the layout before the filters are ordered. That way, the filter type, size and access arrangement can be matched to the booth and the wider workshop rather than chosen in isolation.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier in Hillcrest, Brisbane QLD, and we can help you specify the right filters for spray booth make-up air units in panel shops. Whether you need standard sizes or a custom solution, we can supply or make the right filters for the job.

Call 07 3800 3448 or request a quote. You can also view our products or contact us for help with your next project.