Do air filters remove odors?

It is true that air filters for odors can get rid of odor, but only if it is purposed to trap the gas rather than the particles. A regular HEPA filter is incapable of getting rid of the huge majority of odors because they are in gases. In order to effectively get rid of odor you need to use some adsorption material that would catch the gas molecules while the air is moving through the filter.

Although many people ask "do air filters remove odors," it is necessary to state that the answer to such a question is not simple. The process of odor removal requires the gas phase filtration which involves matching the specific filter media with the gas molecule chemistry; a question about air filters for odors is therefore a question about media selection.

In this article, the principles of the process will be explained as well as comparison of the various types of filters will be given along with practical tips on how to select, install and maintain an activated carbon air filter.

Short answer: some air filters remove odors, but only those built to trap gases rather than particles. A regular HEPA filter alone cannot remove the huge majority of smells, because odorous compounds are gases. Effective odor removal needs an adsorption medium, most commonly activated carbon, that catches gas molecules as air passes through.

_9fjc_dIm3s

How odor removal works in air filters

The principle of odor removal in air filtration is different when compared to the principle of particle capturing. Odor comes from the volatile substances which are gases and vapors, meaning that their dimensions are so small that it is impossible to catch them mechanically, so particle media alone never act as an air purifier for smells.

For example, the size of one molecule of hydrogen sulfide is about 0.00036 microns; on the other hand, the smallest size of the particle that can be collected by a HEPA filter is 0.3 microns.

The difference in sizes explains why HEPA filter odor removal does not work when used on its own. The HEPA filter is effective in the removal of the particles, but in this case gas molecules pass through the fibrous structure.

As a result, there is a necessity to find the filter which would provide the contact between gas molecules and the adsorbent surface. These filters operate through the process of absorption or adsorption, which allows them to capture odors in any HVAC odor removal or industrial air filtration application. The effectiveness of odor filtering relies on all of the following factors: contaminant type, chosen media, contact time and concentration of the odor source.

How filters capture odor-causing gases

Adsorption is the main process used by most of the odor-filtration media. The molecules of the gas will stick to the surface of the material instead of dissolving into the bulk of it. For example, activated carbon is the most common adsorbent because 1 gram of activated carbon has more than 1000 square meters of the area to adsorb gas [2], which is why an activated carbon air filter is the default choice for odour duties.

Gas absorption is absolutely different: it means that the gas molecules will be inside the volume of the material in the same way water dissolves sugar. However, some kinds of filters work by combining absorption and adsorption by the use of chemically impregnated media, and that is the distinction which HEPA filter odor removal claims usually blur.

If odorous air passes through the carbon bed, the molecules of gases diffuse inside the pores and stick to the surface due to the van der Waals forces. The cleaned air is released from the filter, and the odor level decreases. The process goes on until the adsorption sites are saturated, which is called breakthrough, the point that sizing for industrial air filtration must anticipate.

Why odor source and airflow affect performance

Identifying the source of the odor is essential when choosing any kind of odor-removing device. Different odor sources produce different chemicals, and media that can remove one type of pollutant will not work with another one. For instance, virgin carbon has a great capacity to adsorb various VOCs but it will require impregnation to neutralize ammonia effectively [4]. That single mismatch is the most common reason an air filter for chemical odors fails in service.

The air flow determines the volume of air that carries odor in a determined amount of time through the treatment system. In highly variable levels of air flow, the effective contact time reduces and consequently the capture efficiency, which is why an HVAC odor removal duty is always sized on peak flow rather than average flow.

For example, if the air flows through 2,000 m³/h of shallow carbon, the odors cannot be eliminated completely. In contrast, the same volume of air that is treated in a deep bed will yield a much more effective system.

Exposure assessment, in turn, is done after the identification of the source of odor. When air flow volume and concentration of odors are identified, engineers calculate the size of the system to be used. The requirements of a workshop using solvents intermittently are different from those of facilities that handle sewage continuously, and both cases call for a documented industrial air filtration calculation.

Filter types for odor control

Different types of filters have different efficiencies. The type of filter determines which impurities will be removed and how long it can operate before needing replacement. The activated carbon air filter is the most commonly used solution; however, there are many other types of filters available for specific situations.

The table below contrasts the most popular types of filters that are currently used for odor removal in residential, commercial and industrial applications. EACH type of filter has its advantages and disadvantages, therefore one should take into consideration the specifications of their use rather than simply look for the cheapest one available. The same logic applies whether the duty is a domestic air purifier for smells or a large cleanroom odor control system.

Table 1: Analysis of various filter types for odor management

Activated carbon and other gas-phase media

The activated carbon filter is the most efficient in combating odors due to its exceptional surface area and exceptional compatibility to different varieties of odors. One gram of activated carbon can give a surface area of 800 to 1500 m², thanks to the activation of pure coconut shell, coal, and wood using steam or chemicals [2]. That surface area is what makes an activated carbon air filter so effective against organic odours.

Different media are picked based on the contaminant. Pure activated carbon can be used for organic vapors and plenty of VOCs. Acid-treated activated carbon can be used to deal with ammonia and amines while basic activated carbon can work against the likes of H₂S and SO₂ [4].

A thin carbon filter can control odors over several days, while a deep bed with 25 mm or more of media can last months. Results from EPA testing of carbon filters showed rapid breakthrough at typical indoor concentrations, which is why the depth of the bed must be matched to the contaminant load [4]. A shallow panel can look adequate on a datasheet yet behave quite differently in HVAC odor removal service.

HEPA filter odor removal and particle control

HEPA filters are built to capture particles, rated to capture 99.97% of particles at 0.3 microns for H13 and at an efficiency of 99.995% for H14 according to the EN 1822 test standard [3]. HEPA filtration is a critical component in cleanrooms, hospitals, in pharmaceutical facilities, and in any environment where controlled particulate contamination must be managed.

However, to clarify odors generated with HEPA filtration is a myth; odor molecules are typically 1,000-10,000 times smaller than any type of particle captured by HEPA media and pass through the media without ever being intercepted. A HEPA stage approach to removing smells will result in disappointed building occupants, and it is the single most common misconception surrounding HEPA filter odor removal.

Nonetheless, this doesn't completely diminish the relevance of HEPA for odor problems. Particulate matter that can carry adsorbed odors, such as dust, smoke particles, and some bioaerosols, will still be removed. Therefore, for complete odor control, use a HEPA stage for particles, and a gas-phase stage for gases. That pairing is what actually delivers cleanroom odor control without weakening the particle classification.

Chemical odors and contaminant-specific filtration

Chemical odors are more challenging to manage than the general household smell, as they typically fall into the category of reactive or toxic compounds. The air filter for chemical odors must be carefully selected based on chemical characteristics of the contaminant, not merely based on the strength or odor smell.

Ammonia constitutes a small and polar molecule, therefore unable to be adsorbed onto virgin carbon; thereby necessitating the use of acid-impregnated carbon. Hydrogen sulfide requires base-impregnated carbon and potassium permanganate. Potassium permanganate as well as specially treated carbon are utilized for formaldehyde removal by means of filtration. Where several compounds are present at once, a single air filter for chemical odors is rarely sufficient.

Table 2: Specific Guidance for Filtration Media Compatibility to Contaminant Class

Matching filter media to chemical odors

The above media compatibility process starts with an analytical identification of contaminants present. Use of gas chromatography or colorimetric tubes enables determination of contaminants in a given environment. The preliminary identification inhibits error in specifying virgin carbon as the media for sediments it cannot properly capture.

A common mistake involves the thinking that one media type is applicable for handling all chemical odors. For instance, use of virgin carbon for low molecular weight compounds will often lead to quick breakthrough. At Deiiang, we encourage that the gas chromatography scan should be conducted on real-time industrial environments. This is necessary because moisture levels in the industrial processes can alter the adsorption capacity of every impregnated media, a point that industrial air filtration designs often miss.

Finally, the capacity calculations follow. The relevant formula entails that the contaminant mass rate is used to determine the required media quantity when a certain airflow is applied in the filtration system. Typically, the carbon capacity is 10%–40% of the media's weight [4]. For example, to treat 1 kg/h of VOCs with a capacity of 0.20 kg/kg requires 5 kg of carbon per hour of operation.

Safety limits and mixed contaminant streams

Odor problems in the real world virtually never have a single compound. The emissions from industrial processes involve mixtures of the organic and inorganic gases, which have different adsorption behaviors. Thus, selecting the technology to treat a mixed stream is complicated by the fact that one compound may affect the activity of another in three ways—displace it, modify its adsorption characteristics, and/or react with the adsorbent, so industrial air filtration systems often need a full media test.

The breakthrough of one component can occur before the carbon is saturated with the others. Therefore, single-component data cannot be used directly for mixed streams unless it is confirmed through actual testing or conservative design margins are built into the sizing calculation.

Worker exposure limits should be independently assessed from those for odor thresholds. Specifically, a compound could potentially be detected by smell at a significantly lower or higher concentration than its occupational exposure limit in the workplace. For instance, hydrogen sulfide may deaden a person's sense of smell at elevated concentrations; thus, equipment should be used for monitoring rather than the nose during industrial air filtration commissioning.

HVAC odor removal in buildings

HVAC odor removal addresses building-wide problems by integrating gas-phase filtration into the central air handling system. It is usually more efficient than deploying a portable air purifier for smells in every room, provided the odor source sits inside the building.

Retrofit options depend on system type and available space. Table 3 offers HVAC integration choices for odor elimination and their maintenance implications, and each row can be read as a checklist for HVAC odor removal.

Table 3: HVAC integration options for odor removal

Deiiang catalogue data lists a V-bank combined activated carbon medium filter rated at 3,700 m³/h, suitable for central air handling units. The combined design places particle pre-filtration ahead of the carbon stage, extending media life by removing dust that would otherwise blind the adsorbent surface [5].

Integrating odor filters into HVAC systems

The location of your filter will establish its level of efficiency and accessibility for maintenance purposes. The ideal location would be post-particulate pre-filter but pre-supply fan as this results in the cleanest air, meaning it has the best chance of efficient gas-phase filtration, and the least chance of media shedding into the HVAC odor removal stage.

The amount of air leaking past rather than through the filter is also an important consideration. That is from its own leaks through the frame, 5% leakage will result in 5% less removal efficiency. More importantly though is the quality of the gasketing and frame rigidity being equally important as the filtration media itself.

The energy costs of the fan must also be kept in mind given the resistance created by the carbon. Data from the Deiiang catalog indicate that pre-filters with average efficiency become operational from 50 Pa for F5 and for F8 from 100 Pa. This mechanism helps in keeping the energy consumption of the system low [5]. Fan power therefore always belongs in an HVAC odor removal specification.

Air purifier for smells versus central filtration

While selecting between a portable air treatment system and a central filtration system, the extent of the problem and the existing structures of the building have to be kept in mind. Portable air treatment comes with lower initial costs and flexibility, but it can treat only the area covered by the appliance, which is why an air purifier for smells rarely matches a ducted solution across a whole building.

Portable systems have limitations on areas treated while central systems treat the entire building but need ducts and fan capacity. A portable unit that has a capacity of 300 m³/h can clean an area of 30 m² at normal height. A central system with a capacity of 20,000 m³/h can be used for cleaning all the rooms.

The energy consumed is also different among the two appliances. The portable appliance uses between 30 to 80 W of energy. A central system with the additional load of 1,000 m³/h will affect the power consumed by the fan by 0.5 to 2 kW based on the efficiency. Central systems are normally more efficient in terms of energy consumption per cubic meter treated.

Cleanroom odor control and contamination requirements

Cleanroom odor control is governed by certain specifications that do not apply to other types of ventilation systems. Cleanrooms are categorized based on particle content (iso 14644-1), which has nine classifications [6]. While the particle class is qualified for cleanroom processes, unpleasant smells may be emitted, which is why cleanroom odor control is treated as a separate discipline.

Therefore, measures taken for odor control must not affect the cleanliness of the rooms. Introducing media in gas phase into cleanrooms brings several issues like media shedding, pressure drop and compatibility with classification. Since ISO 14644-1 cannot define chemical nature of particles in air, it means that odor and cleanliness of particles should be treated as separate issues, even though both feed into the same cleanroom odor control strategy.

Balancing odor control with cleanroom classification

Therefore, balancing between odor control and cleanroom classification becomes a challenge of keeping conditions clean and process requirements at the same time. Media made in gas phase that may shed particles cannot be installed downstream the last HEPA filter. Pre-filtration stages or specific exhaust treatment have safer locations for media for odor removal. That compromise is what cleanroom odor control usually looks like once a strict particle class has to be protected.

In this case, the Deiiang DOP Integrated Filter (H13/H14, EN 1822) is designed for cleanrooms with limited height of civil works. The box shape of the filter includes an air inlet pipe with diameters of 250, 300 or 350 mm, as well as an adjustment valve and a port for DOP tests which is closed with rubber.

Dust-holding capacities in this range start from approximately 680 g and go to about 1500 g. For work in semiconductor and ultra-clean areas, the Deiiang Super High Efficiency Baffle Filter (U15/U16/U17) has very high efficiency rates (99.9999% to 99.999995%) for particles of 0.12 micron. The model with size of 610×610×50 mm has been catalogue-rated for flows of 450 m³/h.

Cleanroom materials, process sources, and project evidence

Process sources usually dominate odor generation in cleanrooms. Solvent vapors from wafer cleaning, formaldehyde from disinfectants, and ammonia from photolithography all produce odors that particle filtration does not address. Materials selection and process containment help decrease the burden on the filter and keep cleanroom odor control within the capacity of the installed stages.

A report concerning a project observed that the cleanroom for pharmaceutical packaging which was designed for class 1000 / iso 6 required both particle control along with the elimination of odors. The facility contained massive amounts of particles present in the air yet had a minimal height of the plenum as well as stringent limits on the drop in pressure therefore stabilizing the laminar flow.

Deiiang executed the provision of a low-profile filter H14 consisting of high-efficiency filters sealed with silicone-free gaskets and F7 pre-filters. Each unit passed DOP scan testing.

Project reports show that the number of particles reduced from iso 7 to ISO 6 resulting in savings in energy which were possible due to minimal drop of pressure present in the design of the cleanroom setup. However, project outcomes do not guarantee that the same outcome will be achieved.

Industrial odor-control system design

In industrial air filtration dedicated to the elimination of odors the systematic design should be adopted due to the high levels of contamination present in the air which is accompanied by the need for adhering to regulations. Generally, industrial systems operate on airflows between 5,000 and 100,000 m³/h guaranteeing efficiency, and that range is why industrial air filtration is designed as a system rather than as a single filter.

For design purposes, it is important to characterize the source, proceed with selection of filters, and determine the operating equipment. Design assumptions should be documented so that future troubleshooting has a clear baseline.

Relevant test standards include EN 1822 and ISO 29463 for high-efficiency classification, and ASHRAE 52.2 for general ventilation efficiency [1][3][7]. No single international standard covers every gas-phase adsorbent, so manufacturer data plus site-specific testing forms the sizing basis for any industrial air filtration project.

Sizing industrial filtration for airflow and contaminant load

The sizing has begun with the flow rate and contaminant load. The airflow is the value which allows to set the face velocity and the contact time, while the contaminant load determines the amount of media that is needed. Both of the values need to be measured or accurately estimated before ordering the equipment, as the price for retrofitting is way higher than for design time corrections.

The formula for the calculations is: mass of the media (kg) is equal to contaminant generation rate (kg/h) times service life (h) divided by the capacity of the media (kg/kg). Thus, for a process producing 2 kg/h of VOCs with a target of 2,000 hours and 0.15 kg/kg of media capacity, we get 2 × 2,000 ÷ 0.15 = 26,667 kg of media.

Contact time is the second critical parameter since normal designs are made for the time from 0.1 to 0.5 seconds. For example, in the case of having a flow rate of 10,000 m³/h through one square meter of the cross-section, the established face velocity is equal to 2.78 m/s, which indicates that there should be a depth of a bed equal to 2.78 × 0.2 = 0.556 m.

Selecting equipment for industrial applications

Equipment selection is based on the requirement or duty of usage and constraints. The combined activated carbon medium filter from Deiiang's V-bank has a catalogue rating of 3,700 m³/h for which it can be used in moderate duty industrial applications. For heavier loads, multiple units can be joined in parallel to achieve the required capacity without a heavy drop in pressure [5].

Recently, we used our V-bank filters to ｒｅｐｌａｃｅ a traditional carbon panel system in a project involving a client operating a municipal wastewater treatment plant. The conversion resulted in a 40% greater time spent filtering, while extending the lifespan of the medium from 3 months to 8 months, thereby leading to a reduction in the customer's operating costs.

The context of installation also has an effect on the outcome. Rooftop installations are subject to weather and temperature variations, while installations within plants experience issues with noise and vibration as well as limited access. Thus, determining the specific enclosure as well as the access approach needs to be done thoughtfully for the result to be successful, in addition to taking into account the type of medium used.

Choosing an odor filter and specifying performance

The choice of odor filter should involve expressing the measurable requirements for the filter instead of vague claims regarding performance. The specifications should address key information like the specific contaminants targeted; the efficiency of removal desired; the airflow rate; the maximum pressure drop, the type and quantity of medium used and the expected working life. A specification written this way turns a general air purifier for smells into a verifiable duty.

Deiiang's catalogue information provides information on reliable specifications for making a choice when a domestic air purifier for smells has to be replaced by a specified unit.

The Combined High Efficiency Filter (H13/H14, EN 1822) is designed in 5 different sizes, the smallest one measuring 287×287×292 mm operating at 550 m³/h with a surface area of 4.63 m² and the largest one measuring 592×592×292 mm operating at 2,500 m³/h with 20.04 m² and around 1,200 g dust capacity.

The design of the medium uses ultrafine glass fiber paper with no separator and thermoplastic materials for the support and the sealing. The maximum operating conditions are 70 degrees Celsius with 80 percent relative humidity.

Odor Filtration Specification Checklist

In the case of pre-filtration, Deiiang's medium efficiency bag filter operates at between F5 (45 percent efficiency) and F9 (95 percent efficiency) for 0.5 microns. The 592 x 592 x 381 mm six-bag model has a catalogue rating of 2,050 m³/h and 3.18 m² of media, with initial resistance less than 50 Pa at F5 and below 100 Pa at F8 [5].

Comparing filter specifications and media options

A comparison demonstrates that the selected filter is suitable for the physical constraints and performance. Deiiang's DOP Integrated Filter series allows for compact designs for installations with height constraints where standard depth beds cannot fit in.

The catalogue sizes in the series range from 610 x 610 x 120 mm at 1,000 m³/h with 11.32 m² of media and approximately 680 grams of dust capacity to 1,170 x 570 x 150 mm with a capacity of 2,200 m³/h, 24.74 m² of media and approximately 1,500 grams of dust capacity.

The Super High Efficiency Baffle-Free Filter series may provide ultra-high purity performance (U15 to U17) with 99.999% to 99.999995% efficiency for particles that are 0.12 microns and less. There are various sizes in the system ranging from 320 x 320 x 50 mm with a capacity of 150 m³/h to 915 x 610 x 50 mm with 650 m³/h.

Standards, testing, and supplier documentation

Documentation from suppliers must refer to all applicable standards and provide test results for the specific product supplied. Requesting test documents for each unit instead of generic literature is the quickest way to verify that the stated efficiency class applies to your order.

ASHRAE 52.2 has an established rating system for MERV ratings with cleanroom HEPA and ULPA rated at MERV 17 to MERV 20 [1] and EN 1822 has established the EPA, HEPA and ULPA classification system [3]. ISO 29463 is an international standard [7]. IEST-RP-CC001 covers HEPA/ULPA filtration testing for cleanroom applications [8].

MIL-STD-282 governs DOP testing for high-efficiency filters [9]. The most current standard for general ventilation is ISO 16890 which provides classification of filters based on ePM1, ePM2.5, ePM10 [10]. The previously used EN 779 is no longer in activity and has been replaced by ISO 16890 [11].

Engineers must follow ISO 16890 for new systems, using EN 779 for evaluating and retrofitting older systems that were put in before the change of standards. Mixing both standard systems in one specification can lead to complications in compliance and bid comparisons.

Commissioning, maintenance, and verifying odor reduction

Commissioning verifies that the system in place is working as planned. Odor contamination complaints may still occur despite large capital expenditure if commissioning does not occur. The commission verifies that baseline conditions are recorded onsite to allow performance measurements through time, which is the only way to prove that the specified cleanroom odor control has actually been delivered.

Replacements, if necessary, should be anticipated during commissioning, instead of waiting until there is a failure and having to deal with it during a complaint situation. There is an expectation of transparent reporting.

If the system achieves only 85% odor removal as opposed to the specified 95%, the results should be reported so that immediate remedial actions can be undertaken and/or adjustments made, and not hidden behind a statement of success.

Commissioning and odor-removal verification

All verification begins with a baseline measurement. Before the new odor filtration system is run, the concentrations of odorants in the air stream, air flow velocities, temperature, and humidity are recorded at representative locations in the facility. This baseline will be used as the reference point to compare subsequent performance against, whether the system serves a single air purifier for smells or a full central plant.

After completing the commissioning process, all of the same measurements are again taken under the exact same conditions. The method to calculate removal efficiency is: efficiency (%) = (C_baseline − C_after) ÷ C_baseline × 100. If an odorant is measured at 200 ppb before filtration and at 20 ppb after filtration, then efficiency = (200 − 20) ÷ 200 × 100 = 90%.

Verification visits at 30 days and 90 days after commissioning are used to ensure that there has been no significant change in performance or premature breakthrough. If any efficiency drop exceeds 10 percentage points prior to the next service interval, then an inspection of the media should take place before the next service interval.

Maintenance, breakthrough, and replacement planning

The best indicator of filter condition is the pressure drop trend. A gradual increase in pressure drop indicates that the pre-filter is loading with particles, whereas a sudden change could mean either filter media loss of capacity or bypassing. Use of odor-related indicators, whether instrumental or purely sensory, ensures that loss of contaminant removal capacity is detected before odour complaints recur in an HVAC odor removal installation.

Deiiang filters designate the final resistance values which indicate when the filters need to be replaced. The Combined High Efficiency Filter has a final resistance of between 400 and 600 Pa according to the brand. The final resistances of pre-filters are between 250 and 400 Pa. Exceeding either of these values will simply increase energy consumption without providing any improvement in terms of filtration.

Replacement planning should include the procurement lead time. The delivery of industrial carbon filters may take as long as four to eight weeks on average. The set replacement cycle based on operating hours (instead of waiting for the occurrence of breakthrough) will prevent unpleasant odor occasions and emergency buying, a discipline that matters most in industrial air filtration.

Frequently Asked Questions

The answers provided contain the questions mostly asked by the buyers regarding odor filtration. Every answer herein has been provided in such a way as to differentiate gas-phase odor capture and particle capture as confusion between them is the root cause of failures in the odor filtration sector.

Do air filters remove odors?

Some air filters are capable of eliminating odor, but only the ones using gas-phase media such as activated carbon. Ordinary HEPA filters will be unable to remove odor because they work exclusively with the capture of particles rather than gases.

In order to succeed in removing the odor effectively one should provide the air filter using activated carbon and the filtration stage which corresponds with the contaminants that cause the odor, which is how an activated carbon air filter earns its place.

Which air filters for odors work best?

This will depend on the source of the odor. The standard activated carbon will suit perfectly the majority of organic odors and VOCs, while we need acid-impregnated carbon to remove ammonia and base-impregnated carbon to deal with hydrogen sulfide. The first step consists in determining the nature of the contaminant and only thereafter one must choose the appropriate media accordingly.

Does a HEPA filter remove smells?

No. HEPA filters are 99.97% efficient at 0.3 microns in terms of particulate matter capture but have no efficiency in terms of gaseous odors. This means that HEPA filter odor removal is only helpful when combined with a gas-phase filtration method.

Is an activated carbon air filter effective for chemical odors?

The answer is yes if the carbon type and grade is appropriate for the contaminant. Virgin carbon works well for VOCs and organic vapors but needs impregnated carbons for ammonia and hydrogen sulfide treatments. The specific application, flow rate, and thus capacity also determine actual effectiveness in practice and not just the name of the product.

Can HVAC odor removal solve a persistent building smell?

HVAC odor removal will work as long as the source of the odor is inside the confines of the building (source identification is critical) and the system has sufficient filtration capability to treat the air stream. Persistent odors sometimes need source control alongside filtration; HVAC odor removal is never a substitute for removing the source itself.

How often should odor filters be replaced?

Refer to the manufacturer's stated final resistance for replacement criteria. For high-efficiency models, the final pressure drop should be between 400 and 600 Pa and for pre-filters, the final resistance should be between 250 and 400 Pa. Regular checking of carbon media or scheduled replacement based on hours of use is recommended for the best results, especially where cleanroom odor control depends on a single gas stage.

References

• [1] ASHRAE Standard 52.2 - Method of Testing General Ventilation Air-Cleaning Devices for Removal Efficiency by Particle Size. ASHRAE, Atlanta.
• [2] Carbon Adsorption Fundamentals for Air Treatment Applications. Technical paper on adsorbent surface area and capacity, SAE International.
• [3] EN 1822-1 - High Efficiency Air Filters (EPA, HEPA and ULPA) - Part 1 - Classification, Performance Testing, Marking. CEN, Brussels.
• [4] U.S. EPA - Residential Air Cleaning Devices: A Summary of Available Information. EPA 402-F-09-002.
• [5] Deiiang Cleanroom & Air Filter Product Catalogue - Medium-Efficiency and High-Efficiency Filter Ranges. Deiiang, cleanroomequips.com. Product designer: Jason.peng.
• [6] iso 14644-1:2015 - Cleanrooms and Associated Controlled Environments - Part 1 - Classification of Air Cleanliness by Particle Concentration. ISO, Geneva.
• [7] ISO 29463-1 - High-Efficiency Filters and Filter Media for Removing Particles in Air - Part 1 - Classification, Performance Testing and Marking. ISO, Geneva.
• [8] IEST-RP-CC001 - HEPA and ULPA Filters. Institute of Environmental Sciences and Technology.
• [9] MIL-STD-282 - Filter Units, Protective Clothing, Gas-Mask Components and Related Products: Performance Test Methods. U.S. Department of Defense.
• [10] ISO 16890 - Air Filters for General Ventilation. ISO, Geneva.
• [11] EN 779 - Particulate Air Filters for General Ventilation: Determination of the Filtration Performance. CEN, Brussels. Superseded by ISO 16890.