What are the requirements for ISO 8 filtration?

ISO 8 filtration refers to air filters that meet the ISO 8 classification for filtration efficiency. This classification sets stringent standards for removing particles from the air during ventilation and air conditioning operations. ISO 8 filters are essential components in cleanrooms, hospitals, industrial facilities, and other settings where air purity is critical.

What does ISO 8 filtration classify?

The ISO 8 classification specifies the minimum filtration efficiency that air filters must achieve to control different sized particles:

  • ISO 8 filters must remove at least 95% of particles with a size of 0.3 μm.
  • ISO 8 filters must remove at least 85% of particles with a size of 0.1 μm.

ISO 8 filters are designed to filter out fine particles that can easily bypass filters with larger pores. By capturing ultrafine particles down to 0.1 μm in size, ISO 8 filters prevent the spread of airborne microbes and keep processes free of contamination.

What standards apply to ISO 8 filters?

Manufacturers must test and certify ISO 8 filters according to recognized quality standards. The main standards governing ISO 8 filtration include:

  • ISO 16890-1: Establishes ISO air filter classifications based on particle filtration efficiency, including the ISO 8 rating.
  • EN 1822: European standard that specifies High Efficiency Particulate Air (HEPA) filter requirements.
  • IEST-RP-CC001: Institute of Environmental Sciences and Technology recommended practice covering HEPA and ULPA filter leak testing.
  • IEST-RP-CC007: Institute of Environmental Sciences and Technology recommended practice for filter system maintenance and installation.
  • IEST-RP-CC021: Institute of Environmental Sciences and Technology recommended practice for filter leak scanning and leak testing.

By verifying ISO 8 air filters against these rigorous quality standards, end users can be confident the filters will perform as rated when installed properly.

What are the operational requirements for ISO 8 filtration?

In addition to meeting particle capture efficiency standards during testing, ISO 8 air filters must be operated under suitable conditions to maintain performance:

  • Filters should be installed with proper sealing to prevent air bypass around the filter.
  • Air velocity through the filter should not exceed the maximum rated flow to avoid particulate penetration.
  • Filters should be replaced or maintained before the final pressure drop limit is reached.
  • ISO 8 filtered air systems require high quality filtration of supply air to avoid introducing new contaminants.
  • Filters must be scanned and leak tested after installation according to standards like IEST-RP-CC001 and IEST-RP-CC021.

Facility managers can maximize the useful life of ISO 8 filters by monitoring pressure drop and conducting scan or leak testing at scheduled intervals.

What types of ISO 8 filters are available?

ISO 8 filters are available in a wide range of physical configurations to suit different air handling equipment:

  • Panel filters: Disposable panel filters in standard sizes, ranging from coarse prefilters to fine particulate filters.
  • Rigid box filters: Deeper box-style filters constructed with moisture-resistant materials.
  • Bag filters: Available in header-style or envelope configurations, often with large filtration surface areas.
  • Compact filters: Smaller footprint filters for limited space installations.
  • HEPA/ULPA filters: Fully certified high efficiency and ultra low penetration air filters constructed with microglass or wet-laid paper.
  • Gas phase filters: Filters containing adsorbents like activated carbon to remove gases and odors.
  • Auto roll filters: Continuous media on a roll that advances incrementally as filter life is exhausted.

Certain specialty filter types like HEPA and ULPA filters may exceed ISO 8 particle capture requirements. The optimal filter configuration depends on the air handling equipment, flow rate, space constraints, and filtration goals.

What media is used in ISO 8 air filters?

The filter media is the material inside the filter that captures particles. ISO 8 filters use various media tailored to achieve high particle capture efficiency:

  • Fiberglass: Durable glass fibers with tightly controlled fiber diameter and density.
  • Synthetic media: Made from materials such as polyester with precision fiber engineering.
  • Wet laid microglass: Glass microfibers dispersed in water, then formed into paper-like sheets.
  • Membranes: Extremely fine fibers produce porous membrane structures.
  • Nanofibers: Fibers produced on a nanoscale using electrospinning methods.

Synthetic media and microglass are common in panel filters, while fiberglass and robust wet laid media are found in bag filters. Nanofiber and membrane media are newer developments that can potentially enhance filter efficiency and longevity.

What are the efficiency ranges for ISO 8 filters?

While ISO 8 is the minimum certification, filters are available in higher ISO classifications for more demanding controlled environments. The particle size efficiency ranges for fine filtration levels include:

Filter Class Efficiency for 0.4 μm Particles
ISO 8 ≥95%
ISO 9 ≥95%
ISO 10 ≥99.5%
ISO 11 ≥99.95%
ISO 12 ≥99.995%

The higher ISO classes target smaller particles, reaching efficiency levels over 99.99% at 0.1-0.2 μm particle sizes. Critical applications like pharmaceutical manufacturing and microelectronics fabrication employ ISO 14 (99.995% for MPPS) filters.

How is filter capacity determined and rated?

Filter capacity indicates the lifetime or loading ability of a filter before reaching its maximum pressure drop limit. Several methods evaluate capacity:

  • Dust holding capacity (DHC): Measures mass of test dust captured per unit media area before specified pressure drop limit.
  • Arrestance: Measures the fraction of challenge dust retained by the filter.
  • Dirt holding capacity (DIR): Amount of dirt fed to filter until pressure drop limit.
  • Lifetime testing: Filters run with actual air streams until terminal pressure drop is reached.

ISO 8 filters typically achieve capacity testing results in the 8-12 grams/square foot range for media dust holding capacity based on moderate dust loading conditions.

What factors influence filter lifespan?

Several factors affect the usable lifespan of ISO 8 air filters before requiring replacement:

  • Filtration capacity: Higher capacity media withstands more particle loading without clogging.
  • Flow rate: Higher air velocities decrease lifespan by more rapidly clogging filter media.
  • Particle concentrations: Heavy particle loading will plug filters faster than clean air.
  • Terminal pressure drop: Lifespan ends when filter reaches its maximum accepted pressure drop.
  • Filter maintenance: Filter scan testing and media cleaning can prolong filter lifetime.

ISO 8 filters for general ventilation may operate 6-12 months, while filters in demanding hospital or industrial air handling units may require replacement after just a few months.

What are typical pressure drop ranges for ISO 8 filters?

Pressure drop describes the resistance to airflow through the filter. Lower pressure drops save energy and fan power. ISO 8 filters exhibit the following typical initial pressure drop ranges:

Filter Type Typical Initial Resistance (Pa)
Panel filters 50-100 Pa
Compact filters 70-150 Pa
Bag filters 100-250 Pa
HEPA/ULPA 150-300 Pa

The initial resistance rises as filters load with particles over their lifetime. Pressure drop should be monitored and filters changed once terminal resistance (usually 350-500 Pa) is reached to prevent filter bypass.

What are the guidelines for filter installation and scan testing?

Proper installation is critical for ISO 8 filters to achieve rated efficiency and low leak potential. The main installation guidelines include:

  • Align filter carefully and ensure good fit and sealing in the holding frame to prevent bypass.
  • Install filter according to directional arrows marked on the frame to get proper airflow.
  • Use suitable filter gasketing materials on frames to seal in the media pack.
  • Avoid distortion, bending, or damage to media packs during handling and insertion.
  • Ensure sufficient clearance around filter banks for scan testing and media maintenance.

Installed filters should be scan tested per IEST-RP-CC001 and leak tested per standards like IEST-RP-CC021 at intervals of 6-12 months.

What safety measures apply to ISO 8 filter installation and maintenance?

ISO 8 filters collect hazardous submicron particles, requiring safe handling practices:

  • Allow particulate cake to settle before carefully removing filters to avoid exposure.
  • Wear proper PPE during filter handling, including eye protection, gloves, and respiratory protection.
  • Scan test filters in containment or with suitable exhaust ventilation.
  • Seal used filters in plastic immediately to contain dust and avoid leakage.
  • Dispose of used filters as hazardous waste according to applicable regulations.

Facility personnel handling ISO 8 filters should be properly trained on inhalation risks, filter testing equipment, and personal protective gear requirements.


ISO 8 air filtration provides critical control of submicron particles down to 0.1 μm in size. Robust filter testing standards, precision media materials, advanced nanofiber technology, and proper installation practices enable ISO 8 filters to achieve filtration efficiencies over 95% in real-world conditions. With careful maintenance and testing, ISO 8 filters ensure particulate-free air to protect products, processes, equipment, and people.