Cleanroom Air Filtration a Necessity


Cleanroom Air Filtration the key to an aseptic environment

Cleanroom Air Filtration for cleanrooms is a necessity to business continuity in an aseptic environment. Hepa and Ulpa Cleanroom Air Filtration are used to decrease the amount of particulate in the air. Clean room air filters are characterized and categorized by their anti particulate abilities and their air flow rates. For all cleanrooms that require class 100 or below, it is recommended that the controlled environment utilizes HEPA filtration units for the entire space.

HEPA is an acronym for “High Efficiency Particulate Air” or “High Efficiency Particulate Arrestance.” This acronym refers to a filter that is manufactured, tested, certified, and labeled in accordance with current HEPA filter standards. The minimum HEPA category requires the filter to capture 99.97% of the 0.3-micron (0.000012-inch) particles in the air passing through the filter. Most HEPA Cleanroom Air Filtration units become more efficient as they become dirtier.

Most cleanrooms environments use either HEPA filtration units or ULPA filtration units. HEPA and ULPA Cleanroom Air Filtration remove sub-micron particles from the air, which are too small to see but create BIG problems in many critical manufacturing operations. Read about filter capability and airflow resistance testing.

HEPA and ULPA filtration units capture contaminants that degrade particle-sensitive samples and they also remove bacteria and many viruses and mold spores that contribute to a host of infections. HEPA- or ULPA-based Fan/Filter Units (FFUs) thus can play an important in infection prevention in surgical theaters, ICUs and other medical settings.

High efficiency particulate air (HEPA): High efficiency particulate air (HEPA) clean room air filters are designed to screen particles larger than 0.3 µm with an efficiency of 99.99%. HEPA clean room air filters are used in many industries including, pharmaceutical manufacturing, Bio-Tech, Bio-Electronics, Aerospace, Hospitals, and more. Standard HEPA, High Capacity HEPA, Panel Filters, and High temperature filters are several styles available.

Ultra low penetration air (ULPA): Ultra low particulate air (ULPA) filters are 99.9995% efficient in removing particles 0.12 µm and larger. ULPA filters are used in air filtration and purification systems to control airborne particulate levels and to stop the spread of toxic agents and infectious diseases.

Cleanroom Air Filtration

All air-handling systems serving clean room areas are provided with pre-filters to remove gross contamination and protect the cooling coil and final filter from environmental conditions. The prefilters have a lower efficiency than the one they protect. System employing outside air and return air should have an additional filter of 95% (ASHARE) minimum efficiency. 100% make up air systems supplying air to clean areas should have HEPA clean room air filters on the fan discharge and 95% bag filters on the inlet.

Cleanroom Air Filtration – Filter Effectiveness

The ability of a filter to remove particles from the air is reflected by its efficiency rating. The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) has developed a standard for measuring filter effectiveness. The standard describes test procedures to classify filters in terms of arrestance and efficiency. Two terms are commonly used.

  • Arrestance is the amount of dust removed by the filter, usually represented as a percentage. Since large particles make up most of the weight in an air sample, a filter could remove a fairly high percentage of those particles while having no effect on the numerous small particles in the sample. Thus, filters with an arrestance of 90 percent have little application in clean rooms.
  • Efficiency measures the ability of the filter to remove the fine particles. ASHRAE efficiencies of between 10 percent and 40 percent should remove 20 percent to 40 percent of the 1-micron particles in the air, but hardly any of the 0.3 to 0.5-micron particles. ASHRAE efficiencies of 80 percent to 95 percent can remove 50 percent to 70 percent of the 0.3-micron particles. The text information for instance on the efficiency @ 99.97% and 99.997% of HEPA filters look similar but in reality the difference is not insignificant. A 99.97% efficient filter has a fractional penetration of 0.0003; while a 99.99% filter’s fractional penetration is 0.0001. This means that a 99.99% filter is three times more efficient in removing 0.3- micron particles.

Filter Testing

Absolute filter testing has evolved over the years to accommodate the needs of the various applications in which they are used. Typically the filters are shop tested and only provide the quality certification for required efficiency to the end user.

The efficiency of Cleanroom Air Filtration is of paramount importance and must be measured in an appropriate way: The common five method of filter testing include: