MERV, ISO or Custom Spec? Choosing Filters for Hospitality HVAC Systems

Restaurants, cafes and kitchen-adjacent HVAC systems can be hard on filters. Grease vapour, cooking odours, dust from loading areas and constant operation all affect how a filter performs, so the right specification is usually less about chasing the highest rating and more about matching the filter to the system and the space.

If you are weighing up MERV, ISO or a custom specification, the goal is to keep the selection practical. Start with what the air handling unit can take, what the site needs, and what the mechanical services engineer or building owner expects under the project documents and AS 1668.2:2024 where relevant.

Start with the job the filter has to do

Before comparing rating systems, define the role of the filter in the system. In hospitality settings, that role often changes depending on where the equipment sits and what it serves.

A pre-filter near kitchen-adjacent return air may be there to catch larger dust and lint before they load the final filter. A finer filter may be used where supply air quality matters more, such as dining areas, front-of-house spaces or mixed-use tenancies. In some projects, the focus is on protecting coils, fans and ductwork rather than chasing very fine particle capture.

Useful questions to ask early include:

• •Is the system handling general dining area air, kitchen-adjacent air, or both?
• •Is there grease-laden air nearby that may affect filter loading even if it is not passing through the filter directly?
• •Does the unit have room for a thicker filter or a deeper filter bank?
• •What pressure drop can the fan handle across a clean filter and as it loads?
• •Is there space for gauges or other monitoring so pressure drop can be checked?

If you need help identifying the correct size or style, how to measure an air filter is a practical place to start.

MERV, ISO and EN ratings: what they tell you

MERV and ISO 16890 are both used to describe filter performance, but they do not convert directly. That is one reason it is usually unhelpful to try to swap one system for another by looking for a neat equivalent number.

MERV is common in many HVAC conversations, especially when people are comparing general-purpose filters. ISO 16890 is the newer international approach and is widely referenced when discussing particulate fractions such as ePM1, ePM2.5 and ePM10. Both can help narrow the field, but neither replaces the need to look at the actual product, the airflow, and the system limits.

You may also still see older EN 779 classes such as G3, G4 and F5-F9 used in Australia. These are still familiar shorthand in the market even though EN 779 has been superseded by ISO 16890. That legacy language can be useful when speaking with contractors or sourcing replacement filters, as long as everyone understands it is not a direct one-to-one match with the newer rating systems.

For hospitality HVAC, a good approach is to treat the rating as a starting point rather than the answer.

• •Use the rating to narrow performance bands.
• •Check the filter’s dimensions, frame type and depth.
• •Confirm initial and loaded pressure drop are suitable for the unit.
• •Make sure replacement access is realistic for the site team.

When a standard rating is enough, and when it is not

A standard catalogue filter is often fine for straightforward applications. If the unit is a common size, the airflow is moderate and the site conditions are predictable, a standard MERV or ISO-rated option may be the simplest path.

However, hospitality sites are not always straightforward. Retrofitted tenancies, older plantrooms, awkward access, limited filter housings and mixed air conditions can quickly make a standard option less suitable.

A custom spec may be worth considering when:

• •the filter bank needs an unusual size or depth
• •the frame material needs to suit a specific housing or access arrangement
• •the system needs a staged setup with different filter layers
• •the project documents call for a particular configuration that is not readily available off the shelf
• •the site has recurring fitment issues with standard replacements

Custom does not automatically mean better. It simply means the filter is built to suit the plant and the application rather than forcing the plant to suit a standard product.

If the project involves a non-standard housing or difficult access, custom air filters can be a practical option to explore.

Hospitality-specific considerations that affect filter choice

Cooking environments load filters differently

Restaurants and cafes often sit close to sources of fine dust, grease film and odour. Even when grease extract systems are doing their own job, the surrounding HVAC may still see faster loading than a typical office or retail tenancy.

That means the better filter spec is usually the one that balances capture, airflow and maintenance practicality. A higher efficiency filter can be useful, but only if the fan and housing can handle the resistance and the maintenance team can replace it without difficulty.

Odour control is not just about the filter rating

A particle filter can capture airborne dust and other particulates, but odour control often requires a broader system approach. Depending on the site, that may involve ventilation design, source control and other treatment stages rather than simply selecting a finer filter.

This is where the mechanical services engineer’s input matters. The filter spec should fit the overall design intent, not replace it.

Access matters as much as performance

In busy venues, a filter that is hard to inspect often becomes a filter that is neglected. A simple, accessible filter arrangement is usually easier to keep in service.

Good maintenance planning includes:

• •checking the housing arrangement and access clearances
• •confirming the filter can be removed without damaging seals or frames
• •monitoring pressure drop where gauges are fitted
• •following the filter and equipment manufacturer instructions
• •adjusting inspection frequency to suit site conditions and dust load

Some filters are designed to be washable - check the product instructions before assuming a reusable option is suitable for the job.

What about HEPA?

HEPA is not the default answer for hospitality HVAC. It is a specialist filter type used where very fine particulate capture is required and where the system is designed for the associated resistance and sealing requirements.

If HEPA is part of the specification, the standard details matter. Under EN 1822, H13 filters are at least 99.95% efficient and H14 filters are at least 99.995% efficient at the most penetrating particle size (MPPS). Those figures are relevant only when the application genuinely calls for that level of performance.

For most restaurants and cafes, the more common decision is not whether to fit HEPA, but whether the system needs a standard coarse or fine filter, a staged arrangement, or a custom-sized replacement that matches the housing correctly.

Choosing the simplest spec that still fits the site

A good filter specification for hospitality is usually the one that is easiest to install, monitor and replace while still meeting the design intent.

In practical terms, that means:

• •choose the lightest specification that still suits the air quality and equipment needs
• •avoid over-specifying a filter that the fan or housing cannot support
• •prefer sizes and constructions that make replacement straightforward
• •keep the spec aligned with the project documentation and site constraints
• •use custom options when the site demands them, not as a default

If you are unsure whether to stay with a known MERV or ISO class, or move to a custom-built filter, it often helps to review the existing housing, the available pressure drop and the maintenance access before deciding.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD. We supply standard and custom solutions for commercial and hospitality HVAC systems, and we can help you match the filter to the application rather than forcing the application to fit the filter.

Call us on 07 3800 3448 or request a quote. You can also view our products or browse the industries we supply if you are planning a broader HVAC filter changeout.