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Filtration - Air

Filtration Media

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Air Filtration

Q:

Appliance: How can the right filter media influence the final performance of vacuum cleaner or room air cleaner?

A:

The filtration efficiency and air flow resistance of the media at a given test face velocity are of primary importance. Both vacuum cleaners and room air cleaners operate at very high face velocities putting higher demands on the performance of the media.

The size of the filter, the effective area, directly affects both the efficiency and the resistance of the filter. The larger the effective filter area, the lower the face velocity, which in turn lowers the resistance of the filter.

Q:

Appliance:  Why do appliances like vacuum cleaners and air purifiers require high performance filter media?

A:

Both filtration applications are driven by consumers who demand higher levels of Indoor Air Quality (IAQ) in the home. Vacuum cleaners must collect dirt while not dispersing these fine particles back into the air. Room air purifiers filter and remove fine particles from the air. For these tasks high levels of filtration, even HEPA or sub HEPA efficiency, with low air resistance is required. Low air resistance allows maximum suction for vacuums while using the least amount of energy and the smallest size of motor.  Similarly, room air cleaners benefit from low resistance media; air can pass through the filter as many times as possible. Both applications have limited space for the filter, so high performance media is needed to achieve the required efficiency and pressure drop.  

Q:

Appliance:  What standards govern filter media for appliance applications?

A:

Potable Room Air Cleaners

ANSI/AHAM AC-1-2006:

Vacuum Cleaners

ASTM 141

ASTM 1411 F2608

ASTM F1977-04 (2010)

Certified Asthma & Allergy friendly Certification Program

Q:

Appliance:  What types of media configurations deliver optimum results for appliances?

A:

Our synthetic pleatable and microfiber glass media are designed for use in a pleated configuration. Technostat media, with its very high efficiency and low air resistance, can be used in a flat sheet configuration as a prefilter or as a post/exhaust filter in vacuum cleaners. Technostat is also available with a pleatable mesh for pleatable configurations. Our meltblown media is often used as a liner in vacuum cleaner bags to increase the efficiency of cellulose paper or synthetic media.

Q:

Appliance:  Does H&V offer membrane media for vacuum cleaner exhaust filters?

A:

While H&V does not manufacture membranes, we offer our patented Nanoweb media made with nanofibers. These media have performance characteristics and pore structure similar to those of membranes and may be a significantly lower priced alternative to membranes in some applications in the micron range of 0.45 to 0.8 micron absolute.

Nanoweb is available in polypropylene and polyester, fiber size of 0.5 microns in both calendared and uncalendared versions.

Q:

Appliance:  Can H&V offer media with a scrim or reinforcing media to enhance durability and pleating characteristics?

 

A:

H&V offers media with scrims in both our glass and meltblown media product lines.

 

Q:

Cleanroom:  What do HEPA and ULPA stand for?

A:

HEPA = High Efficiency Particulate Air
ULPA = Ultra Low Penetration Air

 

Q:

Cleanroom: What standards govern HEPA / ULPA filtration?

A:

The major standard used is the EN1822; an ISO standard has been approved, ISO 29463. Both standards use MPPS as the criteria for the filter classification.

Q:

Cleanroom: What is MPPS?

A:

MPPS : Most Penetrating Particle Size
Looking at the fractional efficiency curve of a filter media (penetration as a function of particle size) a particle size exists that shows the lowest efficiency (highest penetration) under the given test conditions.
It is this minimum efficiency that is used in the classification under EN1822.

Q:

Cleanroom: What type of media can be used for HEPA and ULPA applications?

A:

Media type depends on the filter configuration. There are two major product types used in HEPA and ULPA filters: deep pleat and mini-pleat filters.  Both types of filters require thin and stiff media.

Q:

Cleanroom: Is electrostatically charged media required for HEPA and ULPA applications?

A:

The small particle retention improves when charged is applied to a filter media. As a result, more open structured-media can be used without sacrificing efficiency level.  Pressure drop of the filter will reduce.
However, this charge will naturally dissipate over time due to air contamination, temperature, and humidity.  The efficiency will drop below the initial efficiency level and the filter will not perform as needed.
The EN1822 standard specifies that a filter with a medium containing more than 20 synthetics by weight should be discharged prior testing.

Q:

HVAC: What standards govern HVAC filters and applications?

A:

The major standards used are  Ashrae 52.2 (US) and EN779 (Europe).

Q:

HVAC: Is there a correlation between the ratings assigned by Ashrae 52.2 and EN779?

A:

Although both standards work with similar equipment, the tests performed are different.
Nevertheless there it is possible to cross reference the standards:
EN779                    ASHRAE 52.2
M6                          MERV 11
F7                           MERV 12
F8                           MERV 14
F9                           MERV 15

Q:

HVAC: What type of media can be used for HVAC applications?

A:

Media requirements depend on the filter application. There are two major product types used in HVAC - pleated filters and pocket filters.  For pleated filters a thin, stiff media is needed while pocket filters require a lofty product.

Q:

HVAC: What is the effect of electrostatic charge on media performance?

A:

Electrostatic charge is a treatment given to synthetic media to enhance filtration performance on fine particles. Coarser fibers can be used to create a more open structure resulting in lower pressure drop. 

Typically, electrostatic charged synthetic material loses its charge over time which leads to a significant reduction in performance.  To achieve similar initial performance, mechanical media are made of finer fibers to guarantee a minimum filtration performance throughout the the life of the filter.

Q:

HVAC: Is charge decay considered in filter classification standards?

A:

North American standards do not consider charge decay in filter classification, but refer to a standard test method.  Ashrae 52.2 – Appendix J describes a method to discharge media using 0.03µm KCl particles.  The discharged efficiency obtained this way has no impact on the filter classification.


In Europe there are a number of standards that take discharged efficiency into account in the filter classification:
- P – Mark : a standard mainly used in Scandinavia
- SWKI : a Swiss filtration guideline
- EN779-2012 : the latest revised EN779 standard
- Eurovent 4/11 : an energy classification standard for filters

Q:

HVAC: How are H&V HVAC media rated?  What type of media would H&V recommend for pocket filter and pleated filter applications?

A:

According to North American Ashrae standard 52.2 H&V media performance is in the range of MERV 8 – 15. Following European standard EN779 H&V HVAC media is rated from F6 – F9.

We suggest charged meltblown media and mechanical meltblown media including NanoWave for pocket filter applications.

For pleated filters pleatable glass, pleatble synthetics are available.

Q:

Coalescer: Why does compressed air be purified?

A:

If compressed air is not pure the entering oil will reduce the life time and can can cause leakages. Adsorptive media will lose their adsorptive properties when saturated with oil.

Q:

Coalescer: Why glass media?

A:

The best results have been obtained with glass fiber media which are able to remove oil droplets in the range of less than 0,1µ up to more than 50µ: These are depth filters providing long life.

Q:

Cleanroom: How does coalescing work?

A:

There are mainly 3 physical effects contributing: a) gravity, b) impaction, c) diffusion.

Q:

Coalescer: How important is the air velocity?

A:

Surface area and fine fiber media, in combination with the air velocity will determine the efficiency of the element.

Q:

Engine Intake: Do I need to cure H&V Heavy Duty Air filter media?

A:

1. If your media uses acrylic based resins and is identified as “Low energy”, then the media is already cured sufficiently for the application it was designed for. Additional process warming, either through hot plates, IR heaters, or ovens may be used if desired to better optimize processing without harming the media.

2. If your media uses phenolic resins and is off white / brown in color, then some curing is required. Please contact your account manager for more information.

Q:

Engine Intake: What is a Wire Side mark?

A:

A wire side mark is a line that H&V puts on the downstream side of the media to indicate which side should be oriented to the ‘clean’ or downstream side of the air flow. The wire mark color and spacing is specific to an individual grade, but standard spacing is on 2 inch centers, and standard colors for the line mark are either black or blue ink.

Q:

Engine Intake: What is the usual test standard used to evaluate heavy Duty Air filter media?

A:

ISO 5011 is a globally accepted test standard for either flat sheet or element evaluation of automotive or heavy duty air filter media or filters.

Q:

Gas Turbine/Dust Collector: Do I need to cure H&V Gas Turbine Air filter media?

A:

If your media uses acrylic based resins and is identified as “Low energy”, then the media is already cured sufficiently for the application it was designed for. Additional process warming, either through hot plates, IR heaters, or ovens may be used if desired to better optimized processing without harming the media.

Q:

Gas Turbine/Dust Collector: What is the usual test standard used to evaluate Gas Turbine Air filter media?

A:

ASHRAE 52.2 and EN779 (2012) are the two globally accepted test standards for either flat sheet or element evaluation of HVAC and Gas Turbine air filter media or filters.

Q:

Gas Turbine/Dust Collector: Which grades are best for pulse cleaning gas turbine applications?

A:

H&V has developed the Nanoweb® range of filter media that is expressly made for pulsing applications. The Nanoweb layer is positioned on the dirty or upstream side of the cartridge where it promotes rapid dust cake formation. The rapid formation of the dust cake promotes a very complete pulse cleaning of the cake from the cartridge. This allows an optimized filter service interval and high MERV rating (13 to 15) or F rating (8 to 9) that cannot be obtained without use of nanofibers.

Q:

Medical Equipment: Are there any national or international standards that the media or the filter need to pass in order to be used?

A:

There is an ISO standard test method for testing of medical filter devices – ISO 23328-1. This is a standard TSI 8130 NaCl aerosol efficiency test conducted on the device following its exposure to moisture in a breathing simulator, set up dependent on its intended application. The standard defines only the test method, not any required filtration efficiency levels.

Q:

Medical Equipment: What can affect the final performance of a medical filter?

 

A:

Low breathing resistance is key for medical filtration applications. Technostat, with its low airflow resistance advantage, is widely used in filtration devices produced by leading medical filtration companies for various applications.

Q:

Medical Equipment: What is the advantage of Technostat Plus?

A:

Technostat achieves the same penetration level as standard Technostat with basis weight reduced by 20-25%.

Q:

Medical Equipment: What is the storage shelf life of Technostat media?

 

A:

Technostat is triboelectrically charged and is extremely stable when stored under normal storage conditions in the original package. We recommend storage at a minimum of -20 and a Maximum of 40 °C at less than 80% RH.

Shelf life testing up to 5 years on the efficiency under normal conditions can be provided upon request.

Q:

Molecular Filter Media: What is the difference between chemical filters and molecular filters?

A:

Molecular filters and what are referred to as chemical filters are one and the same. These filters are also called carbon filters, gas-phase filters or adsorptive filters.

Q:

Molecular Filter Media: What is adsorption?

A:

Adsorption is the process by which liquid or gaseous molecules adhere to the inner pore walls of an adsorbent, like activated carbon. This force is known as Van Der Waal force.  

Q:

Molecular Filter Media:  What do molecular filters do?

A:

Molecular filters remove and control odors, VOCs, irritants and toxic gases in indoor spaces.

Q:

Molecular Filter Media:  Can MFM remove oders and particulate in one system?

A:

H&V’s Molecular filter media combines molecular and particulate filtration in one material.

Q:

Molecular Filter Media:  Can I use a filter media with standard activated carbon to handle all molecular contaminants?

 

A:

MFM can be engineered to handle different molecular contaminants. The media choice will depend on if the molecular contaminant is and odor, VOC, acid or base gas.

Q:

Molecular Filter Media:  What are VOCs?

 

A:

Volatile organic compounds (VOCs), natural or synthetic, are emitted as gases from certain solids or liquids. There are millions of different compounds that can be classified as VOCs, some may have short and long term negative effects on your health.  VOCs can off-gas from many different products. Examples include: paints and lacquers, cleaning supplies, pesticides, building material and furnishings, office equipment such as copiers and printers, glues and adhesive, permanent markets.

Q:

Molecular Filter Media: What is the difference between molecular filtration and particulate filtration?

 

A:

 

Molecular Filters

Particulate Filters

Designed to filter gases

Designed to filter particles

Pressure drop remains the same, regardless of loading

Pressure drop gradually increases as filter loads

Filter efficiency decreases over time

Filter efficiency increases over time

Filtration is not visible

Filtration is visible

Standards and test procedures to rate filters still being developed

Existing standards and test procedures to rate filters

Q:

Respiratory Protection: Does H&V have NIOSH or other government approvals on respirator media?

 

A:

Finished facemasks and respirators are certified by NIOSH or government approvals such as EN 149 for disposable mask; the media is not approved.

H&V can make recommendations on the best media to select for a specified facemask or respirator based on filtration efficiency and resistance of the media at a specified test velocity. However it is the responsibility of the facemask manufacturer to certify the performance of their mask and obtain all required government certifications.

Q:

Respiratory Protection: What characteristics can affect the final performance of the mask or respirator?

 

 

A:

The efficiency and resistance of the media at a given test face velocity are of primary importance to the respirator media.

Size, configuration and processing of the media can also affect the final performance in the respirator. The effective filter area directly influences the efficiency and resistance of the facemask. The larger the effective filter area, the lower the face velocity of the air flow through the mask. This consequently increases efficiency and lowers the resistance of the filter.

The processing of the filter through molding, sealing or pleating operations can also affect the performance of the respirator.

Q:

Respiratory Protection: Can the media be molded, sealed, or pleated? 

 

A:

Both meltblown and Technostat can be molded. For molded mask production, H&V recommends 105 - 108 degrees centigrade for 6-8 seconds. These conditions tend not to affect the filtration characteristics of the meltblown or Technostat media, assuming an outer shell of protective nonwoven media is placed between the media and the heated die platens. Care should be taken not to stretch the media causing holes and breakage which will affect the efficiency of the media. Some final products require a sealing of the meltblown or Technostat media. This can be accomplished thermally or ultrasonically.

Our microfiber glass media can be pleated and is recommended for these applications. Technostat and meltblown can also be pleated if the media is supported by a pleating backing layer

Q:

Respiratory Protection: What is the storage shelf life of respirator media?

 

A:

Both our meltblown and Technostat media are electrostatically charged. The electrostatic charge of both media is very stable when stored under normal storage conditions in their original packaging. The media should be stored in a protected environment of UV light, extreme temperatures and influence of moisture.

Q:

Respiratory Protection: What are normal storage conditions for polypropylene meltblown?

 

A:

The media should be stored in its original packaging at temperatures less than or equal to 40 °C and protected from UV light. An already opened package should be repacked for storage to protect it from other environmental deterioration.

The media, by itself, is stable against moisture and excessive humidity. Nevertheless, we recommend that during storage the relative humidity should not exceed 80 %.

Q:

Respiratory Protection: What affects the stability of respiratory media against environmental deterioration and chemical stability?

A:

Mainly two factors determine the stability of a medium:

-       The mechanical/chemical stability, which is related to the stability of the polymer.

-       The stability of the filtration properties is based on the electrostatic charge.

Q:

Respiratory Protection: What temperatures are required to process polypropylene media?

A:

Polypropylene has a melting temperature of 156-160 °C. The polymer can be processed without polymer degradation up to 120 °C for an extended period of time. Below 0°C, polypropylene will become slightly brittle.

Polypropylene is stable against strong mineral acids and bases and many organic solvents. Non-polar solvents can cause swelling or dissolve the polymer.

The stability of polypropylene against UV light is limited. This can cause yellowing of the fibers and a reduction in the mechanical properties.

Q:

Respiratory Protection: Do moisture and heat affect electrostatic charge?

 

A:

Humidity does not affect the filtration characteristics of the media. Even when the media is submerged in water for 24 hours and allowed to dry, the filtration efficiency and pressured drop values are unchanged.  Therefore, once the electrostatic charge is placed on the polymer, humidity has little or no effect.

Alternatively, temperature does affect the filtration characteristics of the media. Heat will lower the efficiency of the media depending on the amount and the time of exposure.

For short exposure times (3 days or less), H&V recommends not to exceed 55 degrees centigrade

Q:

Respiratory Protection: How should Technostat be stored? 

A:

Technostat is triboelectrically charged media and extremely stable when stored under normal storage conditions in the original package. We recommend storage at a minimum of -20 and a Maximum of 40 °C at less than 80% RH.

Shelf life testing up to 5 years on the efficiency under normal conditions can be provided upon request.