Preventing Odour Carryover in Veterinary and Pharmacy Buildings with Better Filtration

Odour complaints in veterinary clinics and pharmacies often start with airflow, not with the odour source itself. When air moves from treatment rooms, stores, dispensary spaces or waste holding areas into public areas, unwanted smells can travel with it if the building is not set up to control pressure and filtration properly.

The good news is that many odour carryover problems can be improved without major disruption. By looking at airflow paths, pressure relationships and filter selection together, operators and facility managers can reduce the chance of odour migration between back-of-house and customer-facing areas.

Why odour carryover happens

Odour moves with air. If a room is under-ventilated, if doors are frequently opened, or if supply and exhaust air are not balanced, air can drift into adjoining spaces instead of staying where it should.

In veterinary and pharmacy buildings, common sources include:

• •animal holding and treatment areas
• •waste storage and cleaning rooms
• •compounding or dispensary back rooms
• •loading areas and delivery entry points
• •bathrooms and staff amenity spaces

Even when the source room is kept clean, odours can still be noticeable if there is a pressure imbalance. For example, if a back room is slightly positive relative to a corridor, air may leak out through door gaps and transfer grilles. If a room is too negative, it can pull air in from wherever it can, which may disrupt the intended airflow pattern.

A well-planned system helps keep air moving in the right direction. That usually means controlling where supply air enters, where return or exhaust air leaves, and how filtered air is distributed across the building.

Airflow design is the first line of control

Filtration matters, but it works best when the overall ventilation layout supports it. In practical terms, that means the mechanical services design should create clear airflow from cleaner areas to less sensitive areas, or contain odorous spaces so they do not influence public zones.

Pressure relationships matter

A common approach is to keep public-facing areas slightly separate from odour-generating spaces. That may involve:

• •supplying conditioned air to customer areas in a controlled way
• •exhausting air from treatment, waste or preparation rooms
• •reducing uncontrolled leakage around doors, penetrations and service openings
• •checking that return air paths do not short-circuit the intended air movement

For veterinary buildings, this may include ensuring air from animal handling or cleaning rooms is not drifting into waiting rooms, consult rooms or reception. For pharmacies, it may mean separating dispensary or storage areas from the front counter and public waiting area.

Doors, seals and building leakage

Better filter selection will not compensate for poor air leakage control. Gaps around doors, unsealed service penetrations and open transfer paths can all allow odour to migrate.

Facility managers should look at:

• •door closers and automatic seals
• •whether doors are held open for long periods
• •penetrations around pipework and cabling
• •the condition of ceiling spaces and access hatches
• •whether there are unintended air paths between rooms

When airflow is controlled, filters have a better chance of doing their job because the system is moving air where it is intended to go rather than letting it leak uncontrolled through the building.

Choosing filters for odour-related applications

Filters do not remove odour by themselves unless the filter media is designed for that purpose. Standard particulate filters are important because they capture airborne dust and other particles, which can carry or hold onto smells. For odour control, some systems also use carbon or other adsorptive media.

The right choice depends on the application, equipment and air handling arrangement.

Particulate filtration still matters

A good particulate filter can help keep supply air cleaner and protect ductwork and components from dust build-up. In odour-sensitive buildings, that is useful because a cleaner system is generally easier to maintain and less likely to recirculate dust and debris.

Depending on the system, you may see filter grades described using older EN 779 classes such as G3, G4 or F5 to F9, or by ISO 16890 classifications. These rating systems do not convert directly, so selection should be made on the basis of the equipment specifications and the performance needed for the site.

Carbon and specialised media filters

If odour is a key issue, ask whether the system can accommodate a filter stage with activated carbon or another adsorptive media. These are commonly used where the goal is to reduce nuisance odours from incoming or recirculated air.

Useful points to check include:

• •the available filter box depth
• •the pressure drop of the selected filter stage
• •whether the housing seals properly
• •whether the fan and system can handle the added resistance
• •whether the media is intended for odour control or just particle capture

Where high-efficiency particle removal is required, HEPA filters may be specified in some systems. If that applies, H13 filters are at least 99.95% efficient at the most penetrating particle size under EN 1822, and H14 filters are at least 99.995% efficient at MPPS. These are specialised products and should only be used where the system is designed for them.

Maintenance and monitoring make a real difference

Even a well-designed system can lose performance if filters are left in too long or if the housing is not sealed correctly. Over time, loaded filters increase resistance, which can alter airflow balance and affect how odours move through the building.

Inspection frequency depends on the system, site conditions and dust load. Follow the filter and equipment manufacturer instructions, and monitor pressure drop where gauges are fitted.

What to check during routine inspections

• •visible dust build-up on filter faces or around the housing
• •pressure drop across the filter bank
• •signs of bypass around the gasket or frame
• •damaged retaining clips, frames or seals
• •odour complaints that appear during peak use periods
• •whether air is still moving in the intended direction

Some filters are designed to be washable - check the product instructions. If a washable product is being used, make sure the cleaning method matches the manufacturer guidance, because improper washing can damage the media or reduce performance.

For sites that rely on regular servicing, it can help to schedule checks alongside broader filter servicing or commercial filter servicing work, so airflow issues are picked up before they become noticeable to staff or customers.

Planning upgrades for existing buildings

Older veterinary clinics and pharmacies often have limited plantroom space, mixed-use tenant fit-outs and ductwork that was not originally designed for tight odour control. In those cases, practical upgrades usually start with a system review rather than a full rebuild.

A mechanical services engineer or building owner should confirm site requirements, including how the ventilation system aligns with AS 1668.2:2024 and any project-specific constraints. From there, the following options may be worth considering:

• •improving the seal of existing filter frames and housings
• •adding or upgrading a carbon stage where odour control is needed
• •checking whether return air should be rerouted or reduced in sensitive areas
• •improving exhaust from source rooms
• •specifying custom sizes to suit non-standard filter racks

If you are unsure what size or style your system needs, you can use how to measure an air filter as a starting point, or talk through the options for custom air filters if the existing equipment is non-standard.

The practical takeaway for operators and contractors

Odour carryover is usually best addressed as a system issue. The most effective approach is to combine sensible airflow design, sound pressure control and the right filter media for the application.

For veterinary and pharmacy buildings, that often means:

• •separating odour sources from public areas as much as the layout allows
• •checking pressure relationships between rooms
• •choosing filters that suit both particulate loading and odour-related needs
• •maintaining housings and seals so air does not bypass the filter
• •reviewing the system when odour complaints increase or room use changes

If the existing setup is struggling, a filter review is often a practical place to start before larger duct or fan changes are considered.

Talk to Total Air Filtration

Total Air Filtration is a family-owned air filter manufacturer and supplier based in Hillcrest, Brisbane QLD, and we can help you choose or make the right filters for your site.

Call 07 3800 3448 or request a quote. You can also contact us or view our products if you are planning a replacement or upgrade.