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The filtration compass

Dr Iyad Al-Attar warns us of the abyss of truth we confront when we deviate from the roadmap for providing clean air and take the fast track to filtration bankruptcy.

| | Mar 8, 2014 | 10:13 am
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If there are people that still question the need for air filtration in our daily lives, then we should remind them of irritation of the nasal passages caused by pollen, dust and its soiling effects, and consider their unpleasant manifestations, such as hay fever and asthma, experienced by many.mar2014-airfiltration01

Truth be told, the case against dust and air pollution is not confined to mere irritation or mild unpleasantness. Silicosis, caused by inhalation of minute particles of silica, and other forms of pneumoconiosis caused by inhalation of dust including, for example, asbestos, coal, metallic particles, decaying organic matter from vegetation or bird droppings, are serious pulmonary diseases. In short, many airborne particles are the source of disabling or fatal illnesses.

Fair cost of filtration

Conducting textbook air filtration can improve the health of human occupants that would, in turn, reduce the loss of productivity [1]. If some argue that improved air filtration incurs additional cost, I invite them to read studies by Fisk and Rosenfeld, where they have estimated that financial benefits resulting from enhancing air quality by virtue of utilising more efficient filtration, may exceed the costs of filtration by a factor of 20 [2]. While highly efficient filters have higher-pressure drop, consequently signifying higher energy costs, the additional cost may be deemed negligible when compared to salaries, rent or health insurance costs [3].

Here, it is important to highlight the positive impact of enhanced air quality on protection of different HVAC and gas turbine segments. Furthermore, the reduction in productivity losses and employee absenteeism due to improved Indoor Air Quality (IAQ) are not to be underestimated. Some other studies [4] have considered filtration economics and highlighted several costs associated with enhancing IAQ via air filtration. A few of them are:

  • Filters
  • Installation frames, racks and housings
  • Appropriate air handling unit upgrades to accommodate increased static pressure as a result of additional filtration stages and/or improved filter class
  • Energy and maintenance

Value versus price

mar2014-airfiltration02It appears to me that we have lost our sense of value in appreciating what is indispensable to humanity. The evidence of climate change owing to human activity is overwhelming. The signs are all around us: Rising temperatures, melting ice, rising sea levels, more droughts, fires, floods and severe storms. If we don’t change our course of action swiftly and sharply, the consequences are going to be terrible. Simply put, what is the price tag for clean atmosphere, air, water, the environment and the sea? We are always ready to pay more for a fashion item. But when it comes to innovation that may not necessarily be visible, yet enhances our quality of life, such as advanced filtration technologies, we tend to regard them as unnecessary. We look down upon filters as expensive items with a simple cleaning function to remove pollutants. Our minds cease to grant air filter the “value” it deserves. We miscalculate the cost by equating price to value, and overlook intellectual properties, technological know-how, research time and capital investments. By doing so, we reinforce the view that filter craftsmanship, quality and performance are peripheral to the selection criteria. We, thus bluntly declare that such critical factors are on the wrong side of our balance sheet. Perhaps, Oscar Wilde was right when he said, “Nowadays people know the price of everything and the value of nothing.”

Filtration bankruptcy

Cost of filters is admittedly not getting any lower, with filter media and frame material, whether metal or otherwise, are increasingly becoming more expensive. The only reduction in price, then, is to perhaps rely on altering performance parameters or extending the lifetime of the filter by any means. When I say any means, it includes doing the unthinkable and washing the disposable filter, as shown in Figure 1, where a pocket filter is left to reach filtration bankruptcy.

Figure 2 shows collapsed pockets, as they were unable to sustain the flow rate (on right side of the figure) compared to reinforced pockets (on the left side of the figure). When pockets are not fully exposed to the air stream, their permeability reduces and the pressure drop of the filter rises accordingly.

Figures 3 and 4 show different stages of dust-loaded fibrous filters in an air handling unit, where in the latter, the fibrous media can barely be seen. In fact, certain studies have shown that dust-loaded filters can be a source of potential re-introduction of particles/pollutants, which negatively impact filtration performance and IAQ [5-9].

Lack of communication – designing in isolation

I get very excited when I hear people talking about “Green” buildings and the advanced methodologies used to optimally achieve it. But how can we achieve such superior objectives when dust and other pollutants are invading our buildings from different directions? Are designers from different departments communicating effectively with each other or are they at all communicating? Are they granting each design parameter its full consideration relative to the others? Who pays for the damage caused due to lack of communication? Why is it difficult for all designers to sit around one table?

If the yardstick to measure success matches the physical reality of design to its process, shouldn’t architects, engineers and consultants work jointly to provide designs that are more accommodating to occupants? It is essential to realise that every building element influences the performance of others is an inescapable fashion. No one is suggesting placing either more or less emphasis on architectural design, engineering fundamentals and/or material selection. They are all equally important. However, the integration of various design parameters is also critically important.10 This requires careful examination of the implications for HVAC equipment selection, ventilation, lighting, thermal control, energy and IAQ. Early considerations of the following parameters are keys to providing a healthy indoor environment and play a significant role in saving capital and operating costs:

  1. Physical and chemical characteristics of the outdoor air
  2. Indoor polluting sources
  3. Appropriate filter selection

I do not blame building owners if they panic when surprises are sprung upon them at the commissioning stage of their building. Now, everybody is forced to sit around the table with blaming fingers ready to point at each other. In the midst of all this, imagine the number of design conflicts and tedious revisions that need to be addressed. And just imagine, in such a stressful discussion environment, how many designers are willing to address whether or not the pre-designed air filtration requirements have been met and what would be the air quality inside the building.

Typically, it seems there is no room in the priority list of such a meeting to accommodate air filter requirements. The only practice that is well rehearsed is conducting meetings to fiercely discuss substantial discounts for filter acquisition. But when considering an air conditioned indoor environment that we spend most of our time in, we all strive for thermal comfort, regardless of the air quality, unless of course, it triggers lung irritation. Therefore, I urge all individuals concerned that before they conduct that “Green Building” meeting, they ought to pay a visit to the air handling units of the concerned building and have their cameras ready, because quite simply, a dusty building cannot be “Green”, can it?

Now, let’s confront the truth, shall we? How can we be morally obligated to prevent people suffering from air pollution when air filters are left to reach the stage of filtration bankruptcy? How can we allow dust to reach air diffusers, human occupants, operating theatres and incubators, and still claim that we have done our filtration homework? How can we wash disposable filters (pockets, minipleat and absolute) and re-install them to attempt to save costs, where we should actually be saving lives? All of the aforementioned symptoms are indicators that we have not only deviated from the roadmap to provide clean air but have also lost our filtration compass.

Dr Iyad Al-Attar is an Air Filtration Consultant. He can be contacted at: iyad@iyadalattar.com

1 – Dockery DW, Pope III CA, Xu X, Spengler JD, Ware JH, Fay ME, et al. An association between air pollution and mortality in six US cities. New England Journal of Medicine 1993; 329(24):1753–9.
2 – Fisk WJ, Rosenfeld AH. Estimates of improved productivity and health from better indoor environments. Indoor Air 1997; 7:158–72.
3 – Fisk WJ, Faulkner D, Palonen J, Seppänen O. Performance and costs of particle air filtration technologies. Indoor Air 2002; 12:223–34.
4 – Bekö G, Clausen G, Weschler CJ. Is the use of particle air filtration justified? Costs and benefits of filtration with regard to health effects, building cleaning and occupant productivity. Building and Environment, Volume 43, Issue 10, October 2008, Pages 1647–1657
5 – Pasanen P, Teijonsalo J, Seppänen O, Ruuskanen J, Kalliokoski P. Increase in perceived odor emissions with loading of ventilation filters. Indoor Air 1994; 4:106–13.
6 – Pasanen P. Emissions from filters and hygiene of air ducts in the ventilation systems of office buildings. Doctoral dissertation, Kuopio University Publications C. Natural and Environmental Sciences, vol. 80; 1998. Pages 1–77.
7 – Clausen G. Ventilation filters and indoor air quality: a review of research from the International Centre for Indoor Environment and Energy. Indoor Air 2004; 14(S7): 202–7.
8 – Bekö G, Halás O. Clausen G, Weschler CJ. Initial studies of oxidation processes on filter surfaces and their impact on perceived air quality. Indoor Air 2006; 16:56–64.
9 – Hyttinen M, Pasanen P, Björkroth M, Kalliokoski P. Odors and volatile organic compounds released from the ventilation filters. Atmospheric Environment 2007; 41(19):4029–39.
10 – ASHRAE, 2009. “Indoor Air Quality Guide, Best Practices for Design, Construction, and Commissioning” ISBN: 978-1-933742-59-5

NOTE: Unless otherwise referenced, the images used in this article are copyright of the author.

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