NO. 2 2 0 1 3
Molecular man DAZED BY HAZE IN SINGAPORE CHALLENGES OF MOLECULAR FILTRATION HOW AIR FILTERS FUNCTION Chris Ecob, Camfil’s Global Business Manager for Molecular Filtration.
CAMFIL – Clean Air Solutions
E d ito r i a l – M a g n us Yn g en EXHIBITIONS 2014 January 22
Taking care of every
filtration need As the new President and CEO of Camfil, it gives me great pleasure to welcome you to AirMail. In this issue, we are making a landing in the world of molecular filtration – one of several clean air solutions offered by our company globally. We are highlighting molecular filtration in light of the growing awareness of poor indoor air quality, especially the presence of gas molecules and their impact on human health. These molecules are much smaller than the finest particles and can quickly penetrate into the bloodstream through the lungs and reach all parts of the body. This is why organizations like WHO are now advising limits for nitrogen oxide, ozone and sulphur dioxide. Our “City” family of filters, and new CamCleaner City air purifiers, are solutions that effectively prevent the spread of harmful molecules and particles through ventilation systems and buildings. We also have molecular filtration solutions for nuclear power stations, industrial manufacturers, waste processors and museums, including vertical deep bed filters to control the release of toxic gases. All of these solutions represent a strategic part of Camfil’s overall range, and in combination with our particle filters – the most comprehensive assortment on the market – we can meet any customer need for clean air. I only hope that more governments and regulators will jump on the bandwagon and understand that good and affordable filtration solutions exist to mitigate the risk to health caused by injurious gases and particles. The overall benefits are improved indoor air quality, a healthier work environment, reduced sick rates and higher productivity.
11-13
CFIA (Food Industry), Rennes, France
16-20
Siemens 501 Users Conference, Palm Springs, CA, U.S.
24-26
HRSG Users Group, Las Vegas, NV, U.S.
26
Expovent, Jönköping, Sweden
March 18-21
Mostra Convegno Expocomfort, Milan, Italy
23-26
Western Turbine Users Conference, Palm Beach, CA, U.S.
27/3-1/4 ACREX India, New Delhi, India April 1-4
Nordbygg, Stockholmsmässan, Sweden
6-10
CTOTF Turbine Forum Trade Show, Palm Springs, CA, U.S.
May 5-7
PowerGen India & Central Asia, New Delhi, India
7-10 ISK-SODEX 2014, Istanbul, Turkey June 3-5 Lounges 2014, Stuttgart, Germany 3-7
PowerGen Europe, Cologne, Germany
16-20
ASME Turbo Expo, Düsseldorf, Germany
17-19
Energy & Environment Expo 2014, London, U.K.
10-12 REVAC’14, Kuala Lumpur, Malaysia 23-26 Frame 6 Users Group, Fort Myers, FL, U.S.
Camfil AirMail is a world-wide p ublication for Camfil customers. Available in nine languages. Published by: Camfil AB, Sveavägen 56E SE-111 34 STOCKHOLM, Sweden Tel +46 8 545 12 500. Fax +46 8 24 96 50 E-mail: info@camfil.se www.camfil.com Publisher: Alain Bérard Senior VP Sales & Marketing Editor: Liza Braaw/Magnus Jerräng Tel +46 8 545 12 513. Fax +46 8 24 96 50 Text: Camfil/Thorn PR Sweden AB Artwork: Kaigan AB
Always customer-centric
When I joined Camfil’s management team in September, I came to a company with a strong heritage as a technology leader and customerfocused company. We aim to preserve and continue this tradition.
Magnus Yngen President and CEO
2 AirMail No. 2 2013
For example, we have strengthened our technology resources by recently ramping up laboratory and test facilities in a number of countries, including Sweden, the U.S., Malaysia and France. These important investments will ensure continuing cutting-edge filter development, long-term product quality and the best solutions for customers. These facilities also enable us to move our know-how as close as possible to customers and markets. As an example, you can read about our test rig for turbine filters. We also aim to remain a customer-centric organization to nurture and develop our relationships and offer new and expanded services. Several customer cases in this issue illustrate our customer focus: how we develop and supply clean air solutions to deal with particle pollution, odour nuisances and potentially hazardous emissions; how we save energy and clean up the work environment for customers. These are just a few examples of how Camfil aims to remain your best clean-air solutions company and partner, wherever you operate, and whatever your filtration need.
Expovent, Gothenburg, Sweden
February
Want to know more? For further information please contact the Camfil s ubs idiary or agent closest to you, or phone, write or fax to Camfil headq uarters. Head Office Camfil AB, Sveavägen 56E, SE-111 34 STOCKHOLM, Sweden. Tel +46 8 545 12 500. Fax +46 8 24 96 50
Dazed by haze in Singapore How do you deal with severe smell and particle pollution from fires when it penetrates homes, hospitals, offices and other commercial buildings, causing concern and discomfort? Or when it affects production at microelectronic plants? For several days in 2013, smoke haze from Indonesia was so bad in Singapore that it prompted action by Camfil and the local environment agency. To the rescue: CamCleaner, the new CamCleaner City, CityPleat™ and Gigapleat™. In late June 2013, Singapore experienced the worst haze in its history, when fires to clear forests and bush in Indonesia produced a huge cloud of ash and gas that pushed over the country and the Malaysian mainland. The record-high level of haze was the result of several contributing factors: very dry weather, wind blowing constantly in the same direction, and a large concentration of fires in a limited area. Haze particles like those experienced in Singapore are generally difficult to remove as they are tiny (like all combustion particles) and usually come in very high concentrations. In situations like these, air handling units (AHUs) in a building ventilation system need particle filters with a high dust-loading capacity, such as glass-fibre Hi-Flo™ bag filters. For example, if AHUs are equipped with poorly designed particle filters with synthetic media and a small media area, the supply air will not be filtered effectively because of the low dust-holding capacity of the filters. As a result, pressure drop will increase rapidly and the filters will eventually lose their electrostatic charge, creating an inefficient system and poorer indoor air quality.
lets, hospitals, offices, schools and nursing homes that sought solutions for the smell and health risks. To help resolve the problem, several CamCleaner City air purifiers with particle and molecular filters were rushed in from Camfil France and immediately delivered upon arrival to customers. Other implemented solutions included the replacement of particle pre-filters with CityPleat combination filters for smell removal at the fresh air inlet of air handling units, while upgrading secondary-stage synthetic filters with high-efficiency glass-fibre pocket filters. Camfil also offers other options like CityFlo™ filters using a combination of glass fibre and activated carbon when the AHU allows only one filter stage. Camfil also teamed up with the Singaporean National Environment Agency and listed its recommended filtration solutions for haze on the agency’s website.
advanced manufacturing companies, especially in the microelectronics industry. Sulphur dioxide is corrosive and creates yield issues in integrated circuit manufacturing. During the June haze craze, Gigapleat Molecular filters for SO2 removal were also delivered on short notice from Camfil’s nearby factory in Malaysia to successfully protect the most sensitive cleanroom applications. Planning proactively
Haze problems increase awareness about the need for effective filtration solutions and standards to maintain high indoor air quality. Today, many building owners, developers and government offices in Singapore are considering the possibility of incorporating Camfil’s haze solutions in their facility provision to prepare for the next haze alert.
Gigapleat protects cleanrooms
Although concentrations of SO2 did not reach dangerous levels for health in Singapore, the sharp increase resulted in some problems for the most
Rapid response effort
On the worst days of haze in June, Camfil’s Singapore office was flooded with phone calls from retail out-
CAMCLEANER REDUCES PARTICLE COUNT SHARPLY Air purifiers like the CamCleaner series are used in all types of indoor spaces. The product comes in a number of sizes for air purification in industrial premises, offices, homes, schools and public environments. Depending on the application, different models and configurations are available for mobile or stationary installation, and for mounting on walls and ceilings (see Camfil’s product catalogue for further information). See also article on page 13. The air purifier’s high particle removal efficiency, combined with molecular filters in the CamCleaner City version, allows efficient removal of all con taminants usually observed during haze, including combustion particles, sulphur dioxide smells, organic smells and nitrogen dioxide. For particle collection, the units recently installed in Singapore clearly demonstrated their capacity. When the haze was worst, CamCleaners reduced the indoor particle count almost five-fold for fine particles and ten-fold for coarse particles, as measured in tests in Camfil’s office space.
AirMail No. 2 2013 3
Protecting artefacts and cultural heritage in museums and art galleries is one of the many applications of molecular filtration.
Molecular filtration – challenges and opportunities By Dr Chris Ecob, Global Business Manager for Molecular Filtration, Camfil Group
The leading organisation respons ible for cataloguing chemicals – the CAS Registry (Chemical Abstract Service) – has more than 73 million unique chemicals in their database and is adding new items at the rate of 15,000 every day. Many of these chemicals never pre-existed in nature and have been created by man in the industrial era. Some chemicals only exist as gases in the air. However, all chemicals, including those that are normally liquids or solids, have to varying degrees the ability to evaporate and become airborne in their molecular form. It is an inescapable fact therefore that all around the globe, there are more chemicals in the air than ever before. Categorising molecules by impact
Airborne molecules may be categorised according to their impact on humans and our world. Responsibility for smell or odour is perhaps the most obvious. The receptor cells in the nose and the human brain are capable of 4 AirMail No. 2 2013
detecting and characterising many different odour types. Some molecules are classified as irritants. In addition to creating an odour response, they stimulate an involuntary and negative reaction from the body. The classic example is activation of the tear ducts when chopping onions. In extreme cases, airborne molecules can be toxic, indeed fatal at a certain concentration if breathed in. Molecules are very small and mobile. Once they enter the nose or mouth they can be easily transported through the respiratory system, pass through the lungs and are transported in the blood to all parts of the body. For this very reason, chemical weapons agents are normally delivered in the molecular form, rather than as particles. The fourth category is corrosive agents and their impact is not on the human body. Rather they are responsible for failure of sensitive electronic equipment and impaired yields from manufacturing processes.
Camfil’s experience and resources
For 50 years, Camfil has been producing effective molecular filtration solutions that eliminate customer problems and enhance human wellbeing. These have included diverse and critical applications such as nuclear power generation, uranium enrichment, airports, conservation of cultural heritage, waste disposal, destruction of chemical weapons and the oil and gas industry. With so many new chemicals entering our world and the inevitable sensitivities that result, new and exciting opportunities for molecular filtration emerge continuously. Camfil operates the industry-leading molecular filtration test laboratory in the Technical Center located in Trosa, Sweden. In this unique facility, molecular filters and filtration medias can be challenged with a huge range of molecules under application in real conditions and their performance monitored using extremely sensitive gas detectors. Camfil is very well equipped and
staffed to meet future molecular filtration challenges. Studies show impact on health
Despite the dynamic nature of the molecular filtration business, one of the greatest opportunities in terms of human health is already known. The presence of airborne molecules and their negative impact on human health is widely recognised. New scientific studies that support the link are published frequently. Authoritative bodies such as the World Health Organization (WHO) and the European Committee for Standardization (CEN) have published guidance on exposure levels to airborne pollutants and mitigation methods. In fact the European Standard EN 13779 references the use of gas (molecular) filters to achieve the highest levels of indoor air quality for buildings in polluted cities. Eliminating three harmful gases
The negative health effects of longtime exposure to particulate pollution
have been well documented in recent years (see page 15 and 16) and particle air filters, such as those in Camfil’s Hi-Flo™ series, effectively remove the most harmful particulate pollutants in ventilation systems to improve indoor air quality in buildings. However, interest is also being focused today on three gases in particular – nitrogen dioxide (NO2), ozone (O3) and sulphur dioxide (SO2). These gases are recognised as being widely present in the environment and for their irritant behaviour on the human respiratory system, leading to negative health effects and having a short-term impact on work performance. Here, it is interesting to note an article titled “Effects of indoor environment on performance”, recently re-published by David P. Wyon and Pawel Wargocki in the journal and website of the Federation of European Heating, Ventilation and Air-condi-
tioning Associations (REHVA). Wyon and Wargocki point out that humans are the most important asset in a building and HVAC engineers have learnt to argue that the costs of thermal and air quality control in a commercial building are outweighed 100 times by the economic value of their positive effects on occupant performance. They also mention that when poor air quality is present, studies have shown that reduced productivity by workers is due to the presence of gases, not particles. For example, a study by Wargocki found that the short-term effects of poor air quality on the performance of school work remained after airborne dust had been removed, so the negative effects observed were attributed to gas-phase air pollutants. The two researchers state that gas-phase pollutants indoors are an underlying mechanism that needs to be investigated further.
The solutions are available
A proven effective molecular filtration solution exists for the three gases noted above. They could be virtually eliminated from the internal environment and millions of people around the world in city centre buildings would experience positive health effects through the application of molecular filtration. This would not be an investment without payback for building owners and occupiers. Human resource is the primary asset in most companies and numerous studies confirm improved indoor air quality will result in productivity enhancement and reduced absenteeism. Perhaps the greatest challenge therefore is to educate governments, regulatory and advisory bodies that effective and affordable solutions to the negative health issues associated with nitrogen dioxide and ozone are readily available and easy to deploy.
Molecular Filtration Solutions
How molecular filters work
Customer applications and the Camfil molecular filtration solutions fall into four broad categories, which may be classified as light, moderate or heavy duty:
Molecular filters rely on the principle of adsorption. In simple terms, this means sticking a molecule onto the surface of another material (the adsorbent).
1. Indoor Air Quality or Comfort applications. The Camfil City family of products p rovides effective control of nitrogen dioxide, ozone and sulphur dioxide, and the broad spectrum adsorbents also provide control of the numerous internal source pollutants such as volatile organic compounds (VOCs) that are unavoidably outgassed by materials used in building construction and finish. 2. Light process applications. In some cases there are defined pollutants that arise from a source associated with the customer activity, or there may be a particular sensitivity (human or process) to the presence of a particular gas. In these situations a solution is provided that focusses on the specific problem. Examples include airports, IVF clinics, protection of cultural heritage and laboratories. The Camfil CamCarb™ range of products provides reliable control of defined molecular pollutants in these situations. 3. Industrial applications. Many industrial processes are heavily regulated to protect the e nvironment. Camfil applies extremely high-efficiency molecular filtration systems that eliminate toxic chemicals from exhaust airstreams to ensure customer operations are compliant with o perating permits. Typical solutions will be the ProCarb range of Vertical Deep Bed (VDBe) filters. User industries include nuclear fuel production, waste reprocessing and food production. 4. Corrosion control. Some heavy industries rely on expensive electronic and electrical equipment to control their processes. This equipment is extremely sensitive to the presence of acidic gases generated by the process. Molecular filtration is applied in the supply air systems to control rooms to prevent deterioration of the equipment and eliminate unplanned shutdown of the customer plant. Typical solutions will be the ProCarb range of Vertical Deep Bed (VDBe) filters. User industries include oil and gas, pulp and paper, metal refining and waste water treatment.
Adsorbents are characterised as being porous; whilst they appear to be solid materials, at the microscopic level their entire structure is actually a complex array of variously sized and inter-linked fissures and holes called pores. The internal surface of the small diameter pores is extremely large and it is in these pores that adsorption processes mainly occur. To reach the fine pores, the con taminant molecules diffuse from the external air through the larger “transport” pores. Broad spectrum behaviour Many adsorbents have an affinity to adsorb a wide range of different molecules and this is referred to as “broad spectrum” behaviour. Some difficult molecules cannot be controlled using standard adsorbents and in these cases the surface properties of the adsorbent may be chemically manipulated to provide very specific or “targeted” adsorption. There are very many commercially available adsorbents, they are typically made from activated carbon or activated alumina. Every one will behave differently towards each of the different molecules in the air. A successful molecular filtration solution will always be fundamentally dependent on the selection of the most appropriate adsorbent. The expert staff in the Camfil molecular filtration test laboratory ensure correct selections are always made.
PORTRAIT – C h r i s eco b
Bryt inte ordet molecular.
Molecular man Not many air filtration companies have a PhD chemist managing their molecular filters. Camfil does and his name is Chris Ecob. AirMail talked to him in Shanghai, China – via video link – where he was working on the international road map for Camfil’s molecular filtration business. Chris Ecob grew up in Bolton, 30 km northwest of Manchester, UK. His childhood interests were influenced by his father, a biology lecturer, who introduced him to the scientific world and nature. This sowed a seed that grew into a passion for chemistry and the great outdoors in adult life. After graduating with a BSc in Chemistry from Durham in 1979, he spent four years at Salford University (1979-83), studying for a PhD degree. He was introduced to molecular filtration and industry through his research project on the use of activated carbon to capture radioactive iodine emissions from nuclear power plants. The carbon manufacturing company sponsoring the programme and lab facilities was a leader in this field at the time. “It was a highly specialised project with many practical aspects – very hands-on. I modified the existing test equipment to facilitate my new area of research. I decided to take a break from my thesis writing when I was offered two attractive positions with the company in R&D and sales. I chose to work as a sales engineer, something which had never really crossed my mind before,” says Chris Ecob.
6 AirMail No. 2 2013
First ozone filter project
This early exposure to nuclear applications and marketing led him to Automet Filtration in 1984, where he immediately took on his first ozone filter case in a rather stressful situation. “I was called in as technical advisor to develop an ozone filter for use in photocopiers produced by a major customer. The project trials had been a failure up to then. Using important knowledge from my PhD studies, I identified the right grade of carbon for the application. Automet sealed a substantial filter supply deal with one of the largest photocopier producers in the world.” This initial contract gave birth to a brandnew product line of activated carbon filters at Automet. “It officially launched my molecular filtration career. I got a good appetite for it,” says Chris Ecob. His Automet career took off quickly and Chris Ecob joined the company’s management. “But I had four years of doctoral research gathering dust and wanted to finish my thesis. I worked for Automet during the day and wrote my thesis during evenings and weekends. I succeeded in getting my PhD in
adsorption processes and molecular filtration from Salford in 1989.”
Road to Camfil
Camfil acquired Automet in 1997. “I was familiar with Camfil and the type of top-end products they produced. The prospect of joining Camfil was exciting and a great opportunity. With Camfil as our owner, we could invest in a new factory – ours was filled to capacity – and the acquisition gave us the flexibility to build the business. Camfil also had experience from molecular filtration, successfully selling filters like CamCarb™.” New owner, new plant and new opportunities: what happened next? “I was fortunate because my background and ‘chemical skillset’ were recognised by Camfil, who had at that time identified the strategic importance of molecular filtration. In fact they had already started to invest in a very high- level test lab for molecular filtration at the Tech Center in Sweden. This lab was opened in 1999 and initially it provided extensive support to our business in the semiconductor industry. Gigasorb®, a licensed product, was a top seller. It later became a proprietary product called Gigapleat™.” Start of an international career
Still based in England, Chris Ecob’s responsi-
PORTRAIT – C h r i s eco b bilities for molecular filtration business grew with the task. As Camfil’s resident molecular filtration “guru”, he started to sell large special projects all around the world. International business travel is now a rigorous routine. “It’s fantastic to travel like this – to take on new challenges, work with my Camfil colleagues and experience new cultures and countries,” he says. His travels take him to Camfil’s markets and the company’s centres of expertise for molecular filtration including Sweden, England, Malaysia and the United States. Typical customers include nuclear power stations, industrial manufacturers, waste processors and museums. Big-selling products include GigaPleat, the City family, CamCarb™ and ProCarb. The latter include increasing international sales of VDBe (vertical deep bed) molecular filter systems to control the release of toxic gases such as toluene diisocyanate (TDI) from processes. “Customers come to us with their technical problems. For example, a pharmaceutical producer might be using a newly created and unique molecule with a very strong and unpleasant odour signature. Our task is to eliminate the smell nuisance to the plant’s neighbours. We are often faced with groundbreaking challenges,” says Chris Ecob. Growing the business
Chris Ecob is currently stationed in the US at Camfil Inc. in New Jersey. His mission is to develop Camfil’s molecular filtration marketing strategy and grow the business profitably all around the world, while maintaining the product portfolio in a healthy condition. “It’s a very demanding job being Global Business Manager, but I love it,” he says. One of the principal influences driving the business is a growing awareness of poor in-
door air quality, especially the presence of molecules and their impact on human health. Simply described, molecules are much smaller than the finest particles and can quickly penetrate into the bloodstream through the lungs and reach all parts of the body. “The health guidance notes published by organisations, such as WHO, are now taking this into account more and more, advising exposure limits for nitrogen dioxide, ozone and sulphur dioxide. When ambient concentrations exceed these limits they recommend that asthmatic children do not exercise outdoors because nitrogen dioxide and ozone can trigger or aggravate asthma. One of the biggest sources of harmful pollutants is diesel combustion,” says Chris Ecob (see his article on molecular filtration on page 4-5). The solutions exist
“I would like government agencies and regulators to really take up the message and understand that good and affordable solutions exist to mitigate the risk to health caused by harmful gases,” Chris Ecob continues. “These filtration solutions exist for any type of building, commercial or public. We know that employees are the No. 1 asset of many companies and organisations. With effective particle and molecular filtration, the immediate payback is higher indoor air quality, which creates a healthier work environment, reduces sick rates and boosts productivity. Many scientific studies have documented this effect, such as David Wyon’s research (see page 5). Other trends helping to grow the molecular filtration business include stricter environmental legislation and the fact that new chemicals are invented every day. New applications are surfacing almost daily. “Camfil has the experience and resources to address all molecular filtration markets and
needs. We are definitely the leading company in terms of sales, R&D capability and product range. We’ve been doing it since the start of Camfil, 50 years ago.” International mountain biker
Chris Ecob is an outdoor man. He prefers the outdoors and enjoys fresh air and a good workout. Mountain biking is an excellent way to do both, he says. “I have several bikes to get off-road to see things you can’t see from a car. You can explore a lot on a bike. I’ve been in the Himalayas, crossed Jordan and Iceland, the High Atlas Mountains in Morocco and the Baja in Mexico.” Asian food is one of his favourites, particularly Indian and Malay cuisine. He reads a lot, picking up a thriller or novel now and then for relief from his tough technical day. “One of the best books I’ve read recently was about Griffith Pugh, the scientist who researched the climbing conditions for Mount Everest in 1953. He pointed out the need for water and an oxygen supply to prevent dehydration and altitude sickness. His science got Sir Edmund Hillary and others to the top of Everest, but he has been virtually forgotten until now,” says Chris Ecob. Will his team keep Camfil at the top of molecular filtration? “Absolutely. I might be the Global Business Manager in charge of this mission, but Camfil’s molecular filtration business is never a oneman show. I work with a team of dedicated and highly qualified people, located throughout our organisation, including three other PhD chemists. I feel honoured and rewarded to have this job,” he ends.
Chris Ecob Nationality: British Age: 55 Position: Global Business Manager for Molecular Products, Camfil Group. Residence: Lives in England. Currently stationed in the US at Camfil in Riverdale, New Jersey. Interests: Outdoor life and mountain biking. “You can explore quite a lot on a bike. I’ve been in the Himalayas, c rossed Jordan and Iceland, the High Atlas Mountains in Morocco and the Baja in Mexico.” On working for Camfil: “I don’t think there is any employee of Camfil who would question that we are the leader in molecular filtration. As Global Business Manager, I consider myself very fortunate to use my PhD qualifications on a daily basis.”
AirMail No. 2 2013 7
C A M FIL FILTE R S c h o o l: M O D U LE 2
How air filters function This is the second module of eight in Camfil’s Filter School series about the world of air filtration technology. The first module (see AirMail No. 1, 2013) described air pollutants and why we need clean air. Module 2 describes the mechanisms and principles of air filtration.
With the Filter School series, you can learn some fundamentals of filtration, get some extra education or just bring yourself up-to-date. Or if you are new to filtration, the articles will give you a “crash course” on the subject. The modules are very general in nature and just teach the basics. The subjects are described in rather popular terms for easy understanding. Let’s get started with Module 2.
The following modules will be offered in future issues of AirMail: Module 1: Airborne Pollutants – Why We Need Clean Air Module 2: How Air Filters Function (featured in this issue) Module 3: Test Methods and Fundamental Concepts Module 4: Fans, Airflows and Energy Calculations Module 5: Certification Systems Module 6: Environmental and Energy Aspects Module 7: Choosing the Right Filter and Filter Class Module 8: Filter Replacement and Service
8 AirMail No. 2 2013
Particles and particle filters
Filter mechanisms and principles
The atmosphere contains a complex mixture of air pollutants ranging from solid substances (particulate matter), gases and fumes, to substances in liquid form (haze, fog, droplets) and radiation (see Module 1). Depending on what is to be protected, filtration is needed to remove some pollutants before the air can be used. The composition and size of atmospheric particles vary considerably. The size varies from a few nanometres (nm) to hundreds of micrometres (μm), making filtration a challenge because of the wide range of particle sizes to deal with. Soot particles, for example, are much smaller than pollen particles. To get a better understanding of the different sizes, let’s pretend that we take one of the smallest particles – soot, for example – and enlarge it to 10 millimetres. In the particle world, bigger particles, such as pollen, would have a diameter of about 100 metres and be as large as the London Eye, if placed next to soot. Or imagine putting a roulette wheel ball next to the Globe Arena in Stockholm. Visually, this illustrates the wide range of particle sizes that a particle filter must capture. Keep also in mind that particles come in different shapes and have varying properties. A filter’s ability to collect particles depends on various physical phenomena, both mechanical and electrical. So how does an air filter function? The following is a brief description of the mechanisms and filtration principles that make it possible to capture a particle or gas.
Different types of filters employ a variety of mechanisms to trap particles. One ordinary type of filter uses filter material (“media”) made of fibre. The most common use fibreglass or polymer fibres. The polymer fibre version is often electrostatically charged. There are quite a few theoretical and experimental studies on air filtration with fibrous media. A filter comprised of fibres utilises several mechanisms to collect particles, which are described in this article. The overall filtration process – the sum of several different mechanisms – is very complicated. A simplified model is often used to calculate the theoretical particle efficiency of a single fibre (the “single-fibre efficiency theory”).
Gravitational settling Large particles clearly tend to fall to the ground: the bigger the particle, the faster it falls. In the context of filtration, this means that large particles precipitate toward the floor and horizontal surfaces. Most particles trapped by gravitational settling are collected before the filter. Gravitational settling functions in all filters and removes coarse particles.
C A M FIL FILTE R S c h o o l: M O D U LE 2
Straining
Total particle efficiency
Straining collects particles with a diameter larger than the d istance between two fibres. The particles cannot pass through the gap. The straining effect is present in all filters and removes coarse particles. The effect depends on the d ensity of the fibre material. Filtering atmospheric particles by straining has a minimum effect because most particulate matter is smaller than 0.1 μm.
Particle
Media
Airstream
Inertial impaction Particles with a mass (weight) and certain speed have momentum that is a measurement of how difficult it is to change an object’s inertia. Particles tend to move uniformly in a straight line. This implies, in p ractice, that large particles cannot manage to follow the stream-lines around the fibre and collide with the fibre instead. Collecting particles by means of inertial impaction increases when the air velocity increases, and when the size or mass of the particle is larger. The thicker the filter material, the bigger the chance the particle will strike a fibre and be c ollected.
Interception
Diffusion
Small particles follow the stream-lines around fibres but are captured when the surface of the particle touches the fibre’s surface. The particle is bound to the fibre by means of an intermolecular force (Van der Waals force*). The finer the fibres, the better the particles are collected with the interception mechanism. Interception is the only mechanism that is not affected by air velocity.
The random movement of air molecules (Brownian movements or motion**) affects particles smaller than 1 μm. When particles move, there is a greater chance they will strike a fibre in a filter. The smaller the particles, the greater the diffusion effect, which also increases as the air velocity slows through the filter, and when a larger number of finer fibres are utilised.
Particle efficiency is therefore the total result of the various filtration mechanisms. Gravitational settling, straining and inertial impaction will have a greater effect on large particles, while the diffusion effect increases with smaller particles. As a consequence, it is most difficult to filter a specific particle size. Depending on the air velocity and filter media, the particle size 0.1-0.3 μm is the most difficult to collect in a filter. This is called MPPS, standing for Most Penetrating Particle Size. An interesting detail: with the exception of electrostatic attraction, filtration to remove the standard reference particle in Europe according to EN 779 – 0.4 μm – is not affected by air velocity because interception is the main mechanism for collecting this size of particle. Filtration becomes more effective as the velocity increases for particles larger than 0.4 μm, but increases at lower velocities when collecting particles smaller than 0.4 μm. Gases and molecular filters
We are fascinated by airborne particles and we can basically remove all atmospheric particles from the air, regardless of their number, size, shape and properties. But gases and molecules pass right through the very best air filters. Molecules are 1,000 to 10,000 times smaller than particles and usually exist in much higher concentrations. How can we remove these incredibly tiny molecules? – by simply using the laws that govern the behaviour of gas molecules. For example, gas molecules do not tolerate being in different concentrations in the same space – they try to even out the concentration. When gas molecules strike an adsorbent, such as activated carbon, which has a very large surface, the gas molecules will diffuse (even out the gas concentration) by seeking out the carbon and fastening to its surface (for more detail, see article on molecular filtration, page 4-5).
Electrostatic attraction Polymer fibres are electrostatically charged. Coarse electrostatic fibres are charged during production. Filters made of this material use an electrostatic mechanism instead of the mechanical principles d escribed above. The electrostatic effect, which is dependent on the charge of the fibres and particles, will increase at reduced air velocity. Aerosols in the atmosphere (fine solid particles, liquid droplets or gases) will quickly impair electrostatic deposition, and because the fibres are coarse, their efficiency can drop sharply. Several studies have shown that the ability of these air filters to remove particles declines quickly in real operating conditions.
*) Van der Waals force is the sum of the attractive or repulsive forces between molecules. **) Brownian motion is a mathematical model used to describe how particles collide with other particles and move in different velocities, in different random directions.
AirMail No. 2 2013 9
N EW S BRIEFS
Air care
for safety at sea
The Finnish Border Guard has taken safety at sea to a new level by installing Camfil’s air filters on board the “Turva”, a specially designed coast guard vessel that will patrol the Baltic. The main mission of the filters is to ensure safe, clean air for crew during potentially hazardous missions. The northern part of the Baltic has become a busy shipping region in recent years. Every day, some 60 tankers and cargo ships operate in the area, primarily between St. Petersburg and Europe. About 40 passenger vessels also cruise the waters, mainly between Tallinn, Helsinki and Stockholm. To keep the seas secure, the Finnish Border Guard is deploying the Turva (Finnish for “safe”) at the end of year 2013 for heavy-duty open-sea patrol. The ship will be used for a variety of duties, including oil and chemical recovery, search and rescue, emergency towing, research projects and underwater assignments. Requirements for environmental friendliness, sea worthiness, energy efficiency and safe operation in accident situations have all been taken extensively into account when designing this environmentally friendly vessel – from the choice of fuel and machinery, to the selection of air filters to eliminate harmful contaminants and pollutants that could be spread through the Turva’s ventilation system. Customized filtration solution
Camfil has delivered the filter units used to protect ventilation functions in chemical accidents and during oil recovery missions. All filter housings are made of stainless steel in one body.
10 AirMail No. 2 2013
Four-stage filtration is employed: air is pre-filtered in Hi-Flo™ F9 bag filters – rated ATEX class II 2 GD IIB – to remove particles, dust, fumes and mists. The second and third stages are deep cell-type molecular filters using mainly broadspectrum activated carbon. Sophisticated equipment is used to monitor and analyse ambient air quality and these filters can be activated quickly, depending on the type of molecular contamination outside the vessel. Final filtration takes place in ATEX II 2 GD IIB-rated HEPA filters with a very large effective filter media area, class H14. Extensive engineering and testing
STX Finland designed this highly advanced vessel (96 metres long and 17 metres wide) in association with the Finnish Border Guard and Finnish government agencies. It was built at the company’s Rauma shipyard. Camfil’s molecular filter specialists around Europe engineered the filter units in close co-operation with the Guard, the STX Rauma shipyard and SYKE (Finnish Environment Institute). Due to their strict Germanischer Lloyd (GL) classification for quality and safety, these critical system components went through very specific testing procedures (vibration and gas tests) at third-party laboratories, including VTT Expert Services Oy, Finland.
High marks for low-energy filters at Imperial College London
Ranked among the world’s best universities, Imperial College London is a science-based institution with a reputation for excellence in teaching and research. The university’s focus on excellence also applies to its CONCOM programme to optimise the efficiency of campus buildings in order to save energy, cut costs and reduce waste. Reducing the energy consumption of ventilation systems is a major area of focus. To investigate this, Imperial College London commissioned ABS Consulting and Camfil to conduct an air filter trial on the air handling units (AHUs) in the Sir Alexander Fleming and Biochemistry buildings. In the trial, existing air filters were replaced with Camfil’s energyefficient Hi-Flo™ M7 12 pocket bag with a higher surface area. The filter positioning arrangement was also changed. The trials were successful, realising a 7% savings in energy consumption while improving indoor air quality. Filter service life was also extended, reducing filter waste disposal. “Now we are rolling out the filter replacement process across campus and expect savings of about GBP 50,000 (EUR 60,000/USD 80,000) a year, or around 250 tonnes of CO2,” says Dimitra Diamantopolous, Director at ABS Consulting. Imperial College aims to reduce its carbon footprint by 20% in 2014 and the carbon emissions saved with Camfil’s energy-efficient filters will help the institution reach that goal. AirMail No. 2 2013 11
N EW S BRIEFS
Stress test for your turbine filter?
Bring it on! The advanced test facility at Camfil’s main research hub in Sweden – the Tech Center in Trosa – allows customers to test gas turbine (GT) filters in a specially designed rig under a wide variety of simulated conditions – from monsoons and desert storms, to humid and harsh conditions. Testing in advance documents filter operation and avoids possible disturbances later at the site. Tests also reveal opportunities for improving performance. Camfil’s rig for air intake system testing and inspection – nicknamed the “Stormbringer” – is the only one of its kind in the air filtration industry. Camfil Power Systems provides air intake, acoustic and damper systems for gas turbines and other turbomachinery used in the power generation, oil and gas industries. Thousands of these systems are installed around the world, where they operate around-the-clock in industrial, desert, offshore, rural and arctic environments, making reliability and efficient operation an unquestionable requirement. Air intake filters in these conditions are subjected to enormous stress, and if a filter should malfunction for some reason, it may result in expensive downtime for the turbine operator. This is where simulated tests play a vital role in filter design and optimization. Test rig
The rig, designed by Camfil, tests turbine air filters by simulating the tough climatic conditions where gas turbines are often installed. The rig allows the monitoring of key operating parameters, such as differential pressure, dust holding capacity, efficiency after different dust loading phases and average efficiency, salt removal efficiency, and testing with water spray. The device also allows rapid prototyping, product validation, evaluation of products in use and testing for R&D purposes.
“By simulating, we can study filter performance but also test the strength and long-term durability of GT filters in the roughest of ambient conditions.” Richard Ringström, Product Manager at Camfil Power Systems.
“While monitoring pressure drop and filter efficiency, we can also control relative humidity, change temperature, load with dust and spray with saltwater,” says Richard Ringström, Product Manager at Camfil Power Systems. “We can simulate all parameters. That’s why we have nicknamed the rig ‘The Stormbringer’ – it really ‘brings it on’.” 12 AirMail No. 2 2013
Fully automated tests
The filter test rig is designed with easily movable duct sections based on a universal filter holding system. The test procedure is fully automated for dust feeding, pressure drop, DEHS and salt aerosol generation to pre-set levels. Temperatures and humidity can also be varied, as well as pressure drop over a test filter and the particle size for measurement. “The automation of the test facility allows us to run standardized test procedures around the clock,” says Kenny Hedlund, Development Engineer for Camfil. “A filter is tested up to 50 hours and a test cycle can last up to nine days. As an example, we recently used the rig to optimize the filter class for each stage in a three-stage offshore filter system for one of our OEM customers.” Capacity
The test rig has a flow rate ranging from 1,700 to 30,000 m3/hour and a differential pressure from zero up to 12,000 Pa. The rig can simulate winds up to storm strength and subject turbine filters to pressure as high as 400 kg. Three static cassette filters can be tested – also in combination with a horizontal self-cleaning pulse module, or vertical pulse module. The rig also benefits customers in another important way: it allows Camfil Power Systems to quickly develop GT filter prototypes and new products to meet changing requirements and operating environments in an industry where high-performance gas turbines need protection from erosion and fouling for higher efficiency and production economy, and longer running times with lower emissions.
How to linish with a dust-free finish Aluminium linishing is a surface finishing process producing highly explosive dust. When a company on the west coast of Scotland experienced problems with its wet-type dust extractors, it turned to Russell Consulting Scotland Ltd and Camfil Air Pollution Control (APC) to find a solution that would deal effectively with the dust, improve the work environment and reduce maintenance costs. The end-customer, a leading global development partner in the avionics and automotive industry, is ranked among the top three systems suppliers worldwide for engine com ponents, including piston systems, cylinder components and valve trains. Their facility in Scotland manufactures precision bearings for the automotive industry. The wet-type dust extractors used to control dust from their aluminium linishing operations were noisy, inefficient and had to be cleaned out at least once a week. However, one of the biggest issues was that the extractors did
not comply with local Scottish emission regulations. Custom-designed solution
Russell Consulting, a specialist in local exhaust ventilation systems, contacted Camfil APC to find the best solution to meet the customer’s challenges. Camfil APC proposed a high-tech, custom-designed dust extraction system based on a Gold Series™ GS16 dust collector incorporating an integral drop-out section. With this arrangement, large volumes of aluminium dust are removed from the airstream before the air passes through the collector’s carbon-impregnated HemiPleat™ Gold Cone™ filter cartridges. The solution reduces dust loading on the cartridges and also extends filter life. On a weekly basis, more than 1,000 kg of collected material discharges from the collector via three rotary valves into one-cubic-metre flexible bags.
The outside installation of the Gold Series GS16 dust collector saves space, reduces noise and provides a cleaner work environment.
ATEX-compliant
The system, compliant with the EU directive (ATEX) for equipment in workplaces with an explosive atmosphere, included an access platform and an energy-saving variable speed drive controlled by a differential pressure monitor. Today, operators are protected from exposure to dust generated during the linishing process. The GS16 solution
Molecular goes mobile! The world’s first mobile air purifier with molecular filtration – CamCleaner City – was recently used to tackle some difficult indoor air quality (IAQ) situations in France. The two cases below briefly describe how the new CamCleaner City proved to be a simple, quick and powerful solution to eliminate troubling odours and molecular gas, improving the work environment considerably for building occupants – in one case by reducing an unhealthy concentration of formaldehyde on the premises. EADS (the European Aeronautic and Defence Company), a global leader in aerospace, defence and related services, has an office building in Suresnes, near Paris, where employees started to complain of odours and poor indoor quality. The source was the plumbing system in the building. In addition, there was a bad smell on the fourth floor of
the building from glue used during the renovation of the first floor. The odours negatively affected the efficiency of the staff and resulted in additional maintenance costs for extra cleaning of the building’s plumbing system. Camfil France investigated the situation and installed a new-generation CamCleaner City air purifier on the landing of the fourth floor stairway. Eliminating the smell with CamCleaner was beneficial in several ways: in addition to providing a better work environment and improved indoor air quality for staff, plumbing maintenance work was reduced for the facility management company. Filtering away formaldehyde
At the office building of the French national organization for veterans (ONAC) in Metz, employees complained of headaches during work
has created a better work environment, cut maintenance costs and enabled the customer to meet the emissions regulations of the Scottish Environment Protection Agency (SEPA). Unwanted downtime is also avoided: production no longer has to be shut down each week to clean the dust collector – the case with the former wet-type extractors.
CamCleaner City and CityCheck
hours. Camfil France tested the indoor air quality of five office spaces using Camfil’s CityCheck sampling kit. The results indicated poor IAQ in four offices, due to the presence of formaldehyde in a concentration of about 40 μg/m3 – four times the permitted limit value (10 μg/m3) stated in the health guidelines of the World Health Organization. Camfil France installed CamCleaner City with molecular filters targeting the formaldehyde molecules and H13 HEPA filters for particles. After installation, the formaldehyde concentration was reduced to a safe level and the solution eliminated the headaches and allergic symptoms of the employees, who also noticed a new “fresh air feeling” on the premises.
CamCleaner City is a mobile air purifier using a three-stage filtration system to remove particle and gaseous pollutants in indoor spaces. Due to its size and small footprint, the unit can be easily placed in most types of facilities and premises. CamCleaner City is the only air cleaner on the market that can filter any kind of pollutant, including inert particles, microorganisms, allergens, volatile organic compounds (VOCs) and small and large particles. CityCheck. This air analysis kit from Camfil is used to sample and check indoor air quality. A chemical lab analyses the samples taken with CityCheck and customers receive a detailed report with a full diagnosis of their indoor air quality that lets them know if gaseous pollutant concentrations are too high in the air they breathe. The report also serves as good documentation for implementing additional filtration measures.
AirMail No. 2 2013 13
N EW S BRIEFS
Watts draws line in sand for foundry dust and fumes
In the U.S., Watts® Technologies manufactures waterhandling components with low-lead materials and recently opened a new large state-of-the-art foundry in 2013 on their 42-acre (17 hectare) site in Franklin, New Hampshire. The site’s original foundry, opened in the 1970s, was equipped in 2009 with Camfil Air Pollution Control’s Gold Series™ GS96 dust collector installed on a core knockout system to remove sand from metal castings, a difficult application. A GS12 was also installed on powder paint lines where Watts had problems with other dust collection units. Ventilation Control Products, Inc. and Camfil APC engineered these successful installations and were also chosen to develop the air pollution control solutions for the new facility. Maintaining a clean work environment, facilitating employee safety, and allowing for efficient customer fulfillment were priorities for the new green sand foundry, whose processes include sand, pouring and finishing operations. Sand and clay are used to make castings, generating dust, and finishing on castings creates a lot of bronze
Scan here with your mobile device to see a film about the Watts case.
14 AirMail No. 2 2013
grinding dust. The facility’s melting furnaces also give off smoke and fumes that need to be collected. APC solution
Three Gold Series dust collectors were installed in the new foundry and are now integral to many of the operations at Watts, offering a variety of benefits to employee well-being and the manufacturing process in general. Using its experience from more rigorous applications in mining, Camfil APC installed a GS108 with a mining inlet to handle the large volume of green sand coming into the collector. This sand is difficult to handle because of its higher moisture and clay content and the collector completely eliminates airborne silicates and dust that could contaminate the workplace. For the metal melting system, a large GS96 was installed with a spark trap inlet to combat potential fire hazards. This unit serves different areas of the mill, saving additional energy. A third Gold Series unit, a GS72, was installed for finishing processes, specifically metal grinding and shot blasting, which produce very heavy dust. All Gold Series units installed at the new foundry have a system to modulate the fan speed and maintain constant, static pressure as filter pressure changes. This arrangement saves a great deal on energy and increases filter life. Bin level indicators and rotation sensors prevent downtime and make the units easier to maintain. Saving on heating costs
The HEPA filters on the GS72 and GS108 allow air to be brought into the foundry to save on heating costs during New Hampshire’s brutal winters. Each Gold Series unit moves 50,000 to 60,000 cubic feet (1,415-1,699 m3) per minute of air, which can be redirected back into the facility to heat the building. Watts saved not only the cost of makeup air handlers, but also the huge cost of energy associated with running them. The dust collectors have also created a clean work environment – no respirators are required in the sand handling area, making the workday more comfortable and enjoyable for Watts’s employees.
N EW S BRIEFS
Confirming the dangers of air pollution –
Benefits of lowenergy filtration
Research published in The Lancet and The Lancet Oncology journals in mid-2013 once again underscored the negative health effects of exposure to air pollution. A study of nine European countries concluded that air pollution increases the risk of lung cancer even at levels lower than those recommended by the European Union (25 μg/m3 (micrograms per cubic metre) for PM2.5 particles and 40 μg/m3 for PM10). The recommended limit in Europe is still higher than the World Health Organization’s guideline of 10 μg/m3 for total PM2.5. However, WHO has found no safe level of human exposure down to 8 μg/m3 or below.
The Camfil Group is featured in the 2013 edition of the Global Compact International Yearbook, a publication showcasing examples of businesses that are applying the principles of the UN Global Compact and advancing corporate sustainability. The Yearbook covers key sustainability issues and Camfil’s achievements in air filtration are described in the “Good Practices” section in “Buildings need effective air filters”, an article explaining the dual benefit of using energy-efficient air filtration to lower ventilation costs and improve indoor air quality in buildings.* “Effective air filtration is one of the easiest, cheapest and most readily available clean technologies to decrease the energy consumption of building ventilation systems and increase indoor air quality. Our main message is that Camfil’s eco-designed air filters can make a difference for conserving energy, protecting health and supporting global efforts to fight against climate change,” says Myriam Tryjefaczka, Group Sustainability Manager for Camfil.
again
Higher risk of lung cancer
The study looked at the effect of long-term exposure to nitrogen oxides and PM2.5 and PM10 particulate matter. The researchers found that for every increase of 5 μg/m3 of PM2.5 pollution, the risk of lung cancer rose by 18%. For every increase of 10 μg/m3 in PM10 pollution, the risk increased by 22%. Linked to heart failure
failure. Based on data on heart patients in 12 countries, the research focused on the effects of exposure to carbon monoxide, sulphur dioxide, nitrogen dioxide, ozone, and PM2.5 and PM10 particulate pollution. People with already weakened hearts – who are exposed to these gases and fine particles from vehicular exhaust fumes – are more susceptible to heart failure. These pollutants are particularly harmful, as they tend to penetrate into the lungs and enter the bloodstream. Filters for urban pollution Research confirms the need to “keep the city out” in urban centres for higher indoor air q uality. For this purpose Camfil has developed the “City” series of molecular filters – City-Flo XL™, CityCarb™, City-Flo™ and CitySorb™. These filters combine a high-performance particle filter and highly effective broad-spectrum carbon filter in a single product. They are highly effective against particulates, exhaust fumes and smells. Their highly activated carbon also removes a wide range of volatile organic compounds (VOCs) and even ozone.
explained in Global Compact Yearbook
*Camfil’s contribution is on page 112-113. You can download a free copy of the entire Yearbook from www.camfil.com or www.globalcompactyearbook.com.
The second study linked air pollution to heart
Keep processes clean and secure with ProSafe ™ Manufacturers in the Food & Beverage and Life Science industries have set new standards in product quality and require the cleanest of air because of the specific characteristics of their high-end production processes. Clean air is not only critical for their production – it is business-critical. Products like biopharmaceuticals and food have to be produced according to good manufacturing practices in strictly controlled environments, where very small and undesirable particles can be devastating and lead to contamination, product spoilage and high costs. To meet these stringent requirements for cleanliness and secure processes, Camfil offers the ProSafe range of products to satisfy the most demanding filtration needs, including requirements for safety, traceability, certification and audits. High efficiency and energy savings, combined with easy maintenance and installation, are other recognized benefits associated with ProSafe.
Products
The range includes Opakfil ProSafe, Hi-Cap ProSafe and Hi-Flo ProSafe. These air filters are all designed to meet specific safety requirements in air conditioning applications and cleanroom pre-filtration. For further information visit the dedicated ProSafe page on our website, www.camfil.com, where you can download PDFs of the ProSafe filter range brochure, product datasheets and product certificates. You can also scan the QR code below with a mobile device.
Scan here with your mobile device to find certificates for quality audits and technical information on all ProSafe filters.
AirMail No. 2 2013 15
App from Clean Air in London highlights d angers of PM 2.5 The main mission of Clean Air in London (CAL) is to achieve full compliance with World Health Organization (WHO) guidelines for air quality throughout London and elsewhere. Its immediate priority is to see that air quality laws are enforced rigorously in London in 2013 and beyond. To build public understanding of the dangers of air pollution – and address widespread ignorance of the health risks – CAL has developed a free App for iPhones and iPads that uses a new and innovative “Clean Air in Cities Index” to report the impact of long-term exposure to air pollution on the health of the British population. Users are offered four nearby locations and can choose others. The App displays the populationweighted annual average concen-
trations of dangerous airborne particles (total PM2.5)* for local areas, regions and England as a whole. It also reports the estimated percentage of deaths attributable to long-term exposure to humanmade PM2.5.
1 kg of food and drink 2 litres of liquid, but we breathe 25 kg of air. High quality air filters will ensure that the air you breathe within the workplace is as clear as the water you drink.”
Efficient filters available
After smoking, air pollution is the biggest risk factor for early death in the U.K. “It is vital people are warned about the dangers of air pollution and given advice about protecting themselves and reducing pollution for themselves and others. People
“Efficient filters can capture ultrafine particles (2.5 μm diameter and below), which are the most harmful because they can reach our lungs and diffuse via the bloodstream into vital and sensitive organs,” says Bill Wilkinson, Managing Director of Camfil UK. “Ninety percent of our time is spent indoors and indoor air can be up to 50 times more polluted than outdoor air. Every day we eat about
Building awareness
may be encouraged by this new index and App to consider reducing their day-to-day exposure to outdoor and indoor air pollution,” commented Simon Birkett, Founder and Director of CAL, in a statement when the App was launched. Birkett would like the European Environment Agency or World Health Organization to support the rollout of the App internationally. He believes the App and “Clean Air in Cities Index” are the first to report a long-term public health risk.
How can I try it? The App “Clean Air in Cities” can be downloaded from Apple’s App Store at http://itun.es/i6xj69k. CAL (www.cleanairinlondon.org) hopes to create a desktop version in the near future. Camfil is a Gold Sponsor of Clean Air in London and primarily supports its campaign to build public understanding of indoor air quality.
*The WHO guideline is currently 10 μg/m3 for total PM 2.5, although the organization has found no safe level of human exposure down to 8 μg/m3 or below.
www.camfil.com