10 May 2023

Air Filter Selection Guide

ISO 16890 Air Filter Test Standard

When it comes to selecting HVAC air filters, there are several factors to consider to ensure that you choose the right options for your application:


1. Filter Efficiency
The first selection consideration is the efficiency rating, or the capability of the filter to capture particulate. The higher the efficiency, the more effective the filter will be in capturing smaller particles. You can read more about filter efficiency here.


2. Airflow Resistance
Resistance to airflow is crucial factor to consider when selecting any air filter. Higher efficiency filters generally have a greater resistance to airflow, which brings with it increased energy consumption. Filter selection should also be considered in the context of the HVAC system as a whole, to ensure that the fan and other components can deliver sufficient quantities of air, allowing for the resistance to airflow that the filter(s) present.

The ideal filter selection should deliver a low resistance to airflow to minimise energy costs. A filter that can maintain low resistance for a long period of time, will deliver the lowest costs of operation. You can read more about minimising life cycle costs by clicking here.

3. Particle Size
The size of the particulate that the filters will be exposed to should also be considered when selecting air filters – different filters are designed to capture specific particle sizes. In many cases a multi-stage approach is preferred, with coarse pre-filters removing large particulate and higher efficiency secondary filters positioned downstream to remove finer particulate.

4. Environmental Factors
Local environmental factors, such as the concentration of particulates and proximity to sources of air contamination should also be considered when selecting an air filter. It is important to remember that these factors are variable and will be influenced by factors such as seasonal changes, nearby construction works, time of day, etc.  This should be considered when selecting filtration and planning appropriate maintenance regimes.


Taking these factors into account demonstrates that appropriate filter selection is vital for achieving and maintaining appropriate air quality and optimal system performance. Consideration of filter efficiency, airflow resistance, particulate size and environmental conditions will all be important. The correct selections in the balance of these considerations will ensure that your systems can operate efficiently and effectively to recover lost revenues, reduce costs and deliver improved efficiencies. 

Contact Westbury today to arrange for a FREE of charge site survey to assess how your systems can be optimised.

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