Air filtration and laboratory technology use precise terminology. This glossary from explains the key terms used across our products, testing services, and standards to help you better understand clean air performance.
Air Changes per Hour (ACH)
The number of times the total volume of air within a space is replaced in one hour. ACH is a critical factor in ventilation design, particularly in cleanrooms, laboratories, and healthcare environments.
Airflow Resistance (Pressure Drop)
The reduction in air pressure as air passes through a filter or system component. Higher resistance increases fan energy consumption and operating costs.
Arrestance
A measure of a filter’s ability to remove large, coarse particles from the air, typically expressed as a percentage by weight. Arrestance is commonly used for pre-filters and coarse filtration stages.
Biosafety Cabinet (BSC)
A ventilated enclosure designed to protect laboratory personnel, the environment, and samples from exposure to biological agents. Biosafety cabinets are tested and certified to Australian and international safety standards.
Bypass Leakage
Air that passes around a filter rather than through the filter media, reducing overall filtration effectiveness. Proper sealing and installation are essential to prevent bypass leakage.
Cleanroom
A controlled environment designed to limit airborne particulate contamination to specified levels. Cleanrooms are classified according to ISO standards and require validated filtration and airflow control.
Contaminant Load
The concentration of airborne particles present in a given volume of air, typically measured by mass (mg/m³) or particle count.
Diffusion
A filtration mechanism that captures very small particles (typically below 0.1 microns) as they move randomly due to Brownian motion and collide with filter fibres.
Dust-Holding Capacity
The amount of particulate matter a filter can retain before reaching its final resistance and requiring replacement. High dust-holding capacity extends filter life and reduces maintenance frequency.
Efficiency (Filter Efficiency)
The percentage of airborne particles removed by a filter under standardised test conditions. Efficiency may be measured using gravimetric, opacity, or particle-counting methods depending on the applicable standard.
Electrostatic Filter
A filter that uses static electrical charge to attract and capture airborne particles, often achieving high efficiency with relatively low airflow resistance.
Face Velocity
The speed of air passing through the face of a filter, usually measured in metres per second (m/s). Face velocity affects filter efficiency, resistance, and service life.
Final Resistance
The maximum allowable pressure drop across a filter at the end of its service life, as defined by the manufacturer or applicable standard.
Gravimetric Efficiency
A method of measuring filter performance based on the weight of dust collected by the filter during testing.
HEPA Filter (High Efficiency Particulate Air)
A high-performance air filter capable of removing at least 99.97% of particles measuring 0.3 microns in diameter.
HVAC (Heating, Ventilation and Air Conditioning)
Systems designed to regulate temperature, humidity, and air quality within buildings.
Impaction (Inertial Impaction)
A filtration mechanism where larger particles are unable to follow airflow around filter fibres and collide directly with the media, becoming trapped.
Integrity Testing (Leak Testing)
A test method used to verify that a high-efficiency filter has no leaks or bypass paths around the media, frame, or gasket. Integrity testing typically involves scanning the filter face and perimeter using an aerosol challenge and particle detection equipment.
ISO Cleanroom Classification
An international system (ISO 14644) used to classify cleanrooms based on airborne particle concentration levels.
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Laminar Flow
A uniform, unidirectional airflow pattern used in cleanrooms and laboratories to minimise turbulence and contamination.
Metal Viscous Oil Filter
A reusable filter constructed from metal mesh coated with oil. Particles adhere to the oily surface as air passes through. These filters are commonly used in harsh industrial environments.
MPPS (Most Penetrating Particle Size)
The particle size that is most difficult for a filter to capture, typically around 0.1–0.3 microns for HEPA filters.
NATA (National Association of Testing Authorities, Australia)
Australia’s national accreditation body for laboratories. NATA accreditation confirms that testing is conducted competently and in accordance with ISO/IEC 17025.
Opacity Efficiency (Dust Spot Efficiency)
A measure of how effectively a filter reduces the transmission of light through dust-laden air, commonly used to assess fine filter performance.
Particle Counter
An instrument used to measure the number and size of airborne particles in real time, commonly used in cleanroom validation and filter testing.
Penetration
The percentage of particles that pass through a filter. Penetration is the inverse of efficiency.
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Resistance (Pressure Drop)
The energy required to move air through a filter. Resistance increases as filters load with dust.
Secondary Filter
A filter stage positioned after a pre-filter to remove finer particles and improve overall air quality.
Synthetic Filter Media
Man-made fibres used in modern filters to provide consistent performance, high dust-holding capacity, and controlled airflow resistance.
Type Testing
A form of performance testing conducted on a representative filter sample rather than on every individual filter. Type testing provides general performance data but does not verify the integrity or efficiency of each installed filter.
ULPA Filter (Ultra-Low Penetration Air)
A filter with even higher efficiency than HEPA, typically removing 99.9995% of particles at the MPPS. Used in the most critical contamination-controlled environments.
Ventilation Rate
The volume of air supplied to or removed from a space over a given period, often expressed in litres per second (L/s) or cubic metres per hour (m³/h).
Washable Filter
A filter designed to be cleaned and reused, such as metal viscous oil or certain electrostatic filters.
We don’t currently have any glossary entries for this letter. Check back as we continue to expand this resource.
We don’t currently have any glossary entries for this letter. Check back as we continue to expand this resource.
We don’t currently have any glossary entries for this letter. Check back as we continue to expand this resource.