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Selecting the Right Filtration to Protect Kitchens, Tenants, and Base-Building Assets

Commercial kitchen exhaust systems operate in one of the most aggressive environments in any building. Grease-laden air, high temperatures, and long operating hours place constant stress on hoods, ductwork, dampers, and exhaust fans.

The performance of the entire system is heavily influenced by a single component: the kitchen hood filter. Filter selection directly affects:

Grease accumulation in ducts and risers
Performance of tenant isolation and balancing dampers
Exhaust fan efficiency and reliability
AS 1851 inspection and cleaning frequency
Operational risk for kitchens and landlords

This article outlines the main types of kitchen hood filters, their limitations, and why Shepherd Filters, when installed as a pre-filter in front of baffle filters, are increasingly specified as a best-practice solution in modern commercial and multi-tenant buildings.

Why Kitchen Hood Filters Matter

Kitchen hood filters are the first and most critical line of defence in a kitchen exhaust system. Their role is to:

Capture grease aerosols at the hood
Reduce the amount of grease entering ductwork
Protect exhaust fans and shared risers
Limit downstream maintenance and risk

Once grease passes beyond the hood filters, it does not disappear. It deposits on:

Duct walls and risers
Tenant take-off points
Isolation, balancing, and backdraft dampers
Exhaust fan impellers and housings

This downstream contamination is the root cause of many long-term operational, maintenance, and landlord disputes.

Common Kitchen Hood Filter Types

Mesh Filters

Mesh filters rely on layered metal mesh to trap grease.

Limitations

Poor fine-grease capture
Rapid clogging
High grease carry-over into ducts

Outcome
Low upfront cost but high long-term cleaning and contamination risk.

Baffle Filters

Baffle filters force airflow to change direction, separating heavier grease particles.

Limitations

Fine grease aerosols still pass through
Progressive fouling of ducts and fans

Outcome
Common baseline solution, but inadequate for shared risers or high-use kitchens on their own.

Cyclone / Centrifugal Filters

Cyclone filters use centrifugal force to separate grease.

Limitations

Higher pressure drop
Performance dependent on cleaning discipline

Outcome
Improved grease removal, but inconsistent in real-world operation.

The Recommended Path: Shepherd Filters as a Pre-Filter Stage

Shepherd Filters are installed in front of standard baffle filters as a high-efficiency pre-filter stage.

In this configuration:

Shepherd Filters capture the majority of grease aerosols first
Baffle filters act as a secondary safety stage
Significantly less grease enters the duct system

This two-stage approach provides superior protection compared to baffle filters alone.

Key Advantages

High-efficiency capture of both coarse and fine grease aerosols
Dramatically reduced grease carry-over into ductwork
Cleaner exhaust fans and roof discharges
Reduced AS 1851 cleaning frequency and intensity
Improved long-term reliability of the exhaust system

By removing most grease before it reaches the baffle filters, Shepherd Filters extend the service life of all downstream components.

Importance in Multi-Tenant Exhaust Systems

In shopping centres, food courts, and mixed-use buildings, multiple kitchens often connect to a shared base-building exhaust riser. These systems typically include:

Tenant isolation dampers
Balancing or volume control dampers
Backdraft or non-return dampers

These devices rely on free mechanical movement to maintain:

Correct exhaust balance
Odour separation between tenancies
Isolation capability for maintenance

Impact of Grease on Tenant Dampers

When grease is not properly captured at the hood:

Damper blades become sticky or fouled
Bearings and pivots clog
Dampers seize or drift out of position

This leads to:

Loss of exhaust balance
Reduced hood capture in some kitchens
Odour and smoke complaints
Increased access and maintenance costs

Using Shepherd Filters as a pre-filter significantly reduces grease reaching these dampers, helping preserve system functionality and balance.

Landlord Impact When Grease Is Not Mitigated

In most buildings:

The tenant owns the hood and cooking equipment
The landlord owns the shared riser, tenant dampers, and exhaust fan

When grease bypasses hood filtration, landlords face:

Contamination of shared ductwork
Failure or seizure of tenant dampers
Costly access works for cleaning or replacement
Disputes over responsibility and back-charging
Reduced flexibility in leasing adjacent tenancies

These issues often arise years after tenancy commencement, well beyond defects liability periods.

Specifying Shepherd Filters as a pre-filter helps protect base-building assets and reduce long-term landlord exposure.

Benefits for the Kitchen Operator (Tenant)

Effective hood filtration also delivers direct benefits to the kitchen:

More stable exhaust performance
Reduced smoke and heat spill into the workspace
Fewer unplanned shutdowns for duct or fan cleaning
Lower internal fire risk
Fewer complaints from neighbouring tenants or centre management

For kitchen operators, stopping grease early improves uptime, safety, comfort, and business continuity.

Where to Specify Shepherd Filters in Project Documentation

The responsibility for grease mitigation should be clearly defined at the design and leasing stage to avoid downstream disputes and asset contamination.

1. When the Kitchen Hood Is Being Designed

(Consultant-led or D&C kitchen fitouts)

Where the project scope includes the design of the kitchen hood and exhaust system, Shepherd Filters should be:

Specified directly in the mechanical services design documentation
Shown on the hood schedule and detail drawings
Included in the mechanical specification as a pre-filter installed in front of baffle filters

This ensures:

The correct filtration system is installed from day one
Grease is controlled at the source
Base-building assets are protected

2. When Only the Base-Building Is Being Designed

(Landlord / shopping centre / shell-and-core projects)

Where the landlord designs only the shared exhaust riser and fan system, and the tenant designs the kitchen fitout later, Shepherd Filters should be:

Mandated in the Agreement to Lease (ATL)
Included in the Tenant Design Guidelines
Referenced in the Base-Building Mechanical Brief

Typical wording can require that:

All commercial kitchen hoods connected to the base-building exhaust system shall be fitted with high-efficiency grease pre-filters such as Shepherd Filters installed in front of baffle filters.

This approach:

Protects base-building ductwork, dampers, and exhaust fans
Reduces landlord exposure to grease-related defects
Sets clear expectations for all future tenants

Final Summary

Kitchen hood filters are not a minor accessory. They are a primary control point that determines how much grease enters the exhaust system and who ultimately bears the cost and risk.

Baffle filters alone allow grease to migrate downstream, impacting shared risers, tenant dampers, and exhaust fans.

Shepherd Filters, installed as a pre-filter in front of baffle filters, provide a best-practice solution by capturing grease early, protecting base-building assets, and delivering cleaner, safer, and more predictable outcomes over the life of the building.

Whether specified in the mechanical design or mandated through lease documentation, early inclusion of Shepherd Filters is a simple, low-risk decision that prevents long-term operational and compliance issues.