Air filters
Air filters are used to remove airborne particles and pollutants harmful to health and the environment. Within the filter frame there is a filter medium that captures particles as the air flows. The medium differs in type and efficiency class. Proper pleating of the medium increases filter surface area and reduces pressure drop.
Coarse air filters
Coarse filters, usually used as pre-filters or in the first stage of filtration, have an important role in maintaining optimal air quality and protecting valuable filtration equipment. By capturing larger particles, with a diameter of 10 μm and above, they prevent debris and pollutants from reaching sensitive components within HVAC systems.
Fine air filters
Fine filters are the most common type of filter in air cleaning, used as the second and/or third stage filtration. Fine filtration removes fine, small particles that you cannot see by eye, with particle diameters of 1-10 μm. Ventilation systems, with air handling units, are the main areas of use.
High efficiency air filters
Also known as absolute rated filters, these filters with extremely high particle holding capacity are used as the final stage of filtration, to capture pollutants with the smallest particle diameters. EPA, HEPA and ULPA filters can theoretically remove from 85 % (EPA) up to almost 100 % (ULPA) of dust, pollen, mold, bacteria, and any airborne particles with a size of 0.3 microns (µm).
Gas-phase filtration
Also known as molecular filtration, the gas-phase filtration is the process of using specialized filter media and chemical substances to remove gaseous pollutants from the air. In most gas-phase filtration systems, a substance called a sorbent is used to absorb chemical substances and remove them from indoor air.
Cleanroom Equipment
Laminar flow units and cabins, Safe change filter housing, Fan Filter Units (FFU), HEPA filter boxes and housings, and other cleanroom equipment, are designed and manufactured in accordance with the relevant standards to meet the requirements of process and have different working principles and features complementary to the system.
The importance of air filtration for human health
Air pollution is a cocktail of different particles and gases, both natural and manmade. A major ingredient in this cocktail is PM (aka particulate matter). PM is solid or liquid matter suspended in the air around us and is typically categorised according to its diameter. PM10 is particulate matter under 10 µm; PM2.5 is under 2.5 µm across; and PM1 is smaller than 1 µm.
Understanding the difference between these PM categories is important as they all have a varying level of impact on our health. Particles around 100 µm across are prevented from entering our bodies by our nasal hair. But smaller particles go further. PM10 is trapped in our throat; PM2.5 is caught in the lungs; and PM1 can get past everything to enter the bloodstream. It’s these smaller particles that can really have an adverse effect on our health..
The list of health complaints associated with PM is growing almost continually. PM has been linked with various lung diseases, heart attacks and is classified as a class 1 carcinogen. The World Health Organization ranks air pollution as the greatest environmental risk to human health – accounting for seven million deaths a year. So, the PM in the air around us is a big threat to our health. And that’s why air filtration is very important for human health. Our bodies have in-built defences to protect against particles bigger than PM10, but when it comes to particulate smaller than this, it’s the job of air filters to protect our health.
Types and kinds of air filters
Two basic types of air filters are filters for solid particles and filters for gaseous particles. All filters have the same objective, to capture airborne particles and thereby reduce their concentration in the air. Filters designed to remove solids use fibrous or porous materials which capture particulates such as smoke, dust, pollen, mould, bacteria and viruses. Filters containing an adsorbent or catalyst, such as activated carbon, may remove odours and gaseous pollutants such as volatile organic compounds, H2S, HCN, SO2, Cl2, NO2, NO, mercaptans, acidic gases, ozone. This type of filtration is also referred to as molecular filtration or chemical filtration. Sometimes air filters are designed to capture both solids and gaseous particles. When this is not the case, a particulate filter is highly recommended to be used as a prefilter to molecular filtration. Gaseous particles filters use activated carbon to capture molecules, gases and vapours through a physicochemical process. Depending on the field of application and targeted pollutant, different types of activated carbon may be used.
Particulate filters use synthetic and glass fibre materials, meshed or in a form of a paper, with fine or microscopic perforations to capture particles. This filter medium is often pleated, to get more medium surface available for filtration, and it is held within a frame that is installed in the air filter system. There are also metal mesh mediums, suitable for specific filtering applications. Kinds of filters based on their shape are panel, cassette, bag, rigid, V-Compact, V-Modul, duct and cylindrical. Frame materials are cardboard, wood, plastic, metal (galvanized, aluminium, stainless steel).
For potentially explosive (Ex) types of dust, the ATEX air filters or the IECEx air filters, suitable for explosion hazard zones, must be used. The filter medium must be electrically conductive, and the filter frame must be provided with a grounding cable.
ATEX comes from European laws, while IECEx is an international standard recognized globally and set by the International Electrotechnical Commission (IEC). Both standards employ an almost identical zoning system that categorizes hazardous areas based on the presence of gas or dust, and the level of risk. Either way, electrically dissipative air filters should be used in potentially explosive environments. To prove directive-compliant safety in hazardous zones, these filters should be ATEX-certified or IECEx-certified.
Air filter standards
International test standards classify the air filters. The current international test standard ISO 16890 for coarse and fine air filters, replaced on the 1st of July 2018 the earlier standard EN 779.
There are many standards for HEPA filters, the main two are EN 1822 and ISO 29463, both in use.
The EN 779 standard classifies filters into G1, G2, G3 and G4 for coarse class filters, M5 and M6 for medium efficient class filters, F7, F8 and F9 for fine class filters. The efficiency rating for M5-F9 was based on an average particle size of 0,4 µm (micrometers).
The ISO 16890 standard calculates the degree of filtration based on the particle mass in three different size fractions: PM1 (0,3-1,0 µm), PM2.5 (0,3-2,5 µm) and PM10 (0,3-10 µm). The filter is assigned a filter class in one of these three groups or is classified as a Coarse (coarse filter). So, there is no direct comparison or conversion of the filter classes for these two standards.
Cleanroom equipment
The most common cleanroom equipment are laminar flow units and cabins, Fan Filter Units (FFU), safe change filter housings, HEPA filter boxes and housings.
The laminar flow units and cabins are used for production, weighing, sampling and packaging processes. They consist of prefilters, fans (AC and EC), HEPA filters (H13/H14), lighting fixtures (ceiling or side wall mounted), electric and automatic control systems, PVC transparent curtains, wheels or parts for hanging from ceiling. According to the application, optional accessories like cooling coil, temperature and humidification monitoring can be supplied. These units are available in flexible dimension and in a variety of construction materials, including 304/316 stainless steel and epoxy coated carbon steel. Its design is suitable for use in explosive environments, and they provide safe working zones. Leakage test is made with test aerosol according to ISO 14644-3 for HEPA filters. Optionally safe change (Bag in – Bag out) solutions are available. Filter units achieve ISO Class 5 according to ISO 14644-1 with speed-controlled fans, pre-filter and HEPA filter (H14). Clean-air velocity is about 0,45 m/s (±%20) measured 15-20 cm under the air distributor. Laminar flow cabins with FFU supplies laminar flow achieving positive pressure in the cabin. These models are used for laminar flow purposes. They can be designed in any dimension according to the demand.
Fan filter unit (FFU) is a type of electro-motorized air filtering equipment. It is used to supply purified air by removing harmful airborne particles from recirculating air. The units are installed within the system’s ceiling or floor grid. Units often contain their own pre-filter, HEPA filter and internally controllable fan air distribution. Main characteristics are easy installation into cleanroom grids, snap-in prefilter for easy replacement and maintenance, guaranteed leak-free, self-contained ceiling fan filter unit, low operating cost, AC or EC fans optionally, silent operation (65 dBA), adjustable airflow with variable speed controller on request, differential pressure gauge available on request, replacement HEPA filter from room side or ceiling side, flexible dimensions, uniform air velocity.
Safe change filter housing is designed to capture particles and aerosols, and to protect service staff and environment against unsanitary conditions which may be toxic. Metal body of safe change filter housing has bisulcate flange connection. This structure provides a safe tightness. Filter change is carried out untouched by human hands. Service staff do not have to touch neither filter nor inner side of housing. A pre-filter option is available. Service covers are closed very tightly with spline sealed bolt and cross-slotted bolt. Pollution situation of filters can be monitored with differential pressure nozzles which are on the housing.
Air distribution in cleanrooms are generally made through the HEPA filter installed to its housing. Therefore, selection and assembling of the HEPA filter to its housing without leakage is very important. HEPA filter housing consists of 3 main parts, which are the box, filter and the diffuser. The box has a duct connection port for the air inlet at the top or at the sides. On the room side the diffuser can be selected either with special vanes adapted to cleanrooms or with a perforated plate. Filters can be chosen according to the room class from E10 to U17. All HEPA Filter boxes are tested for leakages with the test groove system. To track filter working conditions, HEPA boxes have nozzles for differential manometer connections. According to the EN 1882 standards, boxes have nozzles for supplying test aerosols (EMERY/DOP). Test grooves that face the HEPA filter gasket achieves air tightness according to DIN 1946 Part 4. Inside of the housing can be easily disinfected and will not be affected by disinfection chemicals.
Frequently asked questions aboutAir filters
What is an air filter?
An air filter is the main component of air filtering device, used to separate out contaminants from air.
How does a media (paper) filter work?
In most filters all these filtration effects are happening at once, giving an overall particle removal efficiency.
How important is clean air for human health?
Clean air is crucial for human health, supporting healthy lungs, brain function, and overall well-being. It helps prevent and reduce the severity of respiratory illnesses like asthma, lung cancer, and cardiovascular diseases. Air pollution can also lead to premature deaths and impact various organ systems, according to the American Lung Association and the World Health Organization (WHO). Every year, millions of adults and children die prematurely from poor air quality. Air pollution results in reduced businesses’ productivity and imposes a heavy economic burden. Cleaner air will help build stronger and more resilient economies.
What is indoor air quality?
Indoor Air Quality (IAQ) refers to the condition of the air within and around homes/buildings, especially as it relates to the health and comfort of the occupants. Good IAQ implies that the air is free from pollutants and contributes to a comfortable and safe living or working environment.
Why should you change your air filters regularly?
- Dirty air filters are top cause for HVAC system failure. A dirty filter prevents the proper airflow into your HVAC air handling system. Restricted airflow creates a strain on the fan motor and over time can lead to motor burnout and possible system failure. Filter replacement is the best option to extend life of the HVAC system.
- Clean air filter makes your fan motor run smoother and consumes less energy. One of the easiest and quickest ways to reduce your energy bill is to replace your air filter.
- Clean air filters improve indoor air quality. Poor air quality can aggravate allergies and asthma, and human health in general.
- Dirty air filters make your heating and air-conditioning systems dirty, and the ducts get dirty more quickly. This can lead to costly maintenance expenses or to a need to replace your units sooner than you expected.
Can air purifiers replace ventilation?
How often does the filter need to be changed?
There are many factors determining when an air filter should be changed, the three most important one are: total time the filter is used, air quality (particles load), humidity. Other factors can vary greatly from application to application. For most prefilters, it is usually recommended to change it every 2-3 months. In many commercial and industrial applications, a filter pressure drop can be monitored, and filters can be changed when they reach their recommended final pressure drop.Za većinu predfiltera, obično se preporučuje da se menjaju svaka 2-3 meseca. U mnogim komercijalnim i industrijskim primenama, pad pritiska filtera može se pratiti, a filteri se mogu menjati kada dostignu preporučeni konačni pad pritiska.