Filters can help ensure the wellbeing of a company’s workforce by removing harmful pollutants and protect the planet by saving energy. TROX UK’s Nick Shackleton explains:

The quality of the air we breathe has a profound impact on the quality of our lives and yet it is something we tend to take for granted. This is surprising given that we spend up to 90 per cent of our lives indoors.

The health effects from indoor air pollutants can include irritation of the eyes, nose, and throat; headaches; dizziness and fatigue, and exposure to poor indoor air quality can result in more serious conditions such as asthma, hypersensitivity pneumonitis, and humidifier fever.

The main barrier to these pollutants and the primary guardian of indoor air quality is the humble air filter.

There are essentially two types:

• Particle air filters: These coarse and fine dust filters are for general applications in air conditioning and ventilation as well as in process technology.
  Testing and classification is according to EN779, which gauges "arrestance" (a measure of a filters' ability to capture and retain a known weight of synthetic dust, fed into the filter at a specific rate to a final differential pressure drop of the filter) and efficiency (using the "atmospheric dust spot efficiency test" which compares the discolouration of a high efficiency filter disc, one upstream and one downstream of the test filter).

• Particulate air filters: HEPA (high efficiency particulate air) and ULPA (ultra low penetration air) filters are high-quality air filters that separate aerosols, toxic dusts, bacteria, etc. and are recommended for areas requiring maximum air purity such as clean rooms.
  Testing and classification is according to EN1882 which lays down a method for testing the filtration efficiency on the basis of particle counting using a liquid test aerosol. This allows uniform classification of the particulate air filters according to the filtration efficiency.
  

Eighty-five per cent of the costs generated by an air filter arise from the energy used during operation of the ventilation system. Acquisition, maintenance and disposal costs make up just 15 per cent of the financial outlay.

That is why it makes sense to focus on the quality of the filter media used in ventilation systems – some are better than others. For example, TROX has developed various classes of bag filters, fine dust filters and high-performance particulate filters which reduce the rise in pressure differentials and so reduce the resistance in the system (see Box 1). This allows TROX filter media to cut energy consumption of some ventilation systems in half compared with traditional filter media.

This is made possible by a manufacturing technique in which variable pleating heights and pleat spacing are made in millimetre steps. This enables us to optimise the filter media to the customer's precise technical requirements in terms of filtering performance, quantity of air and pressure loss. Consequently, the fan output can be reduced, thus saving energy.

So filters do not only contribute to the health of employees; they also contribute to the health of the planet. And that makes them worth serious consideration.

BOX 1

Air filter grades

Grade Arrestance
G1 <65
G2 65<80
G3 80<90
G4 >90

Arrestance is the measure of a filter’s ability to capture and retain a known weight of synthetic dust, fed into the filter at a specific rate to a final differential pressure drop of the filter. Results are expressed as a "by weight" arrestance. Filters in these grades are designed to prevent mechanical system fouling and as pre-filters to secondary and semi-HEPA range.

Grade Efficiency %
F5 40<60
F6 60<80
F7 80<90
F8 90<95
F9 >95

The efficiency test for air filters, referred to as the "atmospheric dust spot efficiency test" in EN779, is carried out using atmospheric air only, and comparing the discolouration of a high efficiency filter disc, one upstream and one downstream of the test filter. Filters in these grades are designed to keep buildings and process spaces clean and free from airborne pollution.

Grade MPPS* %
H10 85
H11 95
H12 99.5
H13 99.95
H14 99.995
* MPPS – Most Penetrating Particle Size

Higher efficiency grades are also available, but these are generally for specialist applications.

How TROX clears the air

TROX UK has launched an air filter division and has appointed as filter development manager Nick Shackleton, who has more than 10 years’ experience in the air filter industry.

He says: “As a direct result of investment in our manufacturing facilities, we are able to offer the customer a selection of filters that maintain the highly engineered standards one would expect from a company such as TROX, but at a competitive price. From lowly G4 panels to the highest grade of ULPA filter, TROX has something to offer customers for every application. When coupled with the range of housings and other air movement products that we manufacture, we feel we have one of the most comprehensive catalogues in the market.”

TROX is a Eurovent-certified manufacturer of fine filters in accordance with EN779. Its products include:

• TROX KSF Safe Change units designed to separate particles and aerosol, and protect maintenance personnel from contaminants from toxic or radioactive systems. The access opening in the filter housing is tightly sealed by a cover plate and uses star knob clamping screws for easy servicing. Effective operational safety is provided as the cover plate can only be replaced when the clamping device is closed and the filter cell correctly positioned. The units can be arranged in a combination of designs to allow for different air volumes or space limitations.
  
• The F654 high efficiency terminal filter with airtight shut-off damper conforming to DIN EN1751 for installation in air conditioning plant where high standards of hygiene are required. The integrated shut-off damper offers significant advantages in terms of project planning, plant operation and maintenance. For example, regular decontamination of the dirty side of the system can easily be carried out with the installed filter cell isolated, and filter changing or other servicing can be carried out without interrupting plant operation.
  
• The F620 pharmaceutical clean air diffuser which has dispensed with the need for a fluid sealing frame to retain the minipleat filter panel. Instead, the minipleat filter panel is manufactured with a new frame profile. The filter housing sealing frame protrudes into the fluid seal ensuring an absolutely tight seal for the minipleat filter panel.
  
• F730 bag filter inserts of synthetic fibre media used in ventilation and air conditioning systems as prefilters or main filters, depending on the filter type, for the extraction of fine dust particles. In order to suit a range of specific requirements, they are available in various efficiency levels and filter surface areas. The filters consist of a front plastic frame (or metal on request) and the individual filter bags made of synthetic fibre media with spun fibre scrim covers.

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