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Air filters in ventilation systems – what for?

Air filters are integral functional components of the household and industrial ventilation and exhaust equipment.

The filtration of plenum and exhaust air is required to clean it from macro and micro contaminants of any nature: sand, dust, aerosol suspended material, smells, smoke, steam, toxic gases, infectious and radioactive particles, etc.

Air filters for the ventilation system of PHAUF brand are manufactured by the Russian-based Research and Production Company MICROSISTEMA LLC.

PHAUF filters:

The quality of PHAUF products meets the strict requirements of the European standard EN 779:2012.

Our company offers the most popular designs of different purity class filters for the ventilation systems.

A brief review of their structure and purposes will help you make the right choice.

Panel filters

A simple air filter of panel design consists in the cut of the filtering fabric fixed with a mesh. The filtering element, in its turn, is fastened with a metal U-shaped frame profile.

Panel filters are installed at the inlet of the airflow to perform basic air cleaning from large contaminants:
- coarse particle dust, mud, sand
- flying insects
- leaves, feathers, fluff, etc.

Advantages of panel filters:

Used for basic (rough) cleaning of the air in residential, public and production premises:

Filtration classes: G2, G3, G4, М5

Subject to regeneration.

Cassette filters

A cassette panel filter is an upgraded panel filter.

The filtering fabric in a cassette filter is fully wrinkled (pleated) and fixed on a corrugated support mesh.

The corrugated filtering element is placed in a metal U-shaped or rigid square frame.

Depending on the nature of the filtering material, cassette filters can be used for both rough and medium air cleaning on the first and second stages of filtration of the plenum and exhaust flow.

They are included into the scope of supply of household and ventilation units of any type.

Filtration classes: G2, G3, G4, М5

Subject to regeneration depending on the model.

Pocket filters

The filtering element of such structures is represented by textured nonwoven fabric sewn in the form of sack pockets fastened to traverses on a rigid frame.

The higher is the number and the depth of pockets, the larger is the area of the filtering surface and the longer is the product service life.

Depending on the type of used filtering material, pocket filters are suitable for the first and second steps of air cleaning.

They are used in different household and industrial plenum and exhaust ventilation systems of buildings and production facilities.

Filtration classes: G3, G4, М5, М6, F7, F8, F9

NOT subject to regeneration

Compact W-shaped filters

In compact W-shaped filters, a pleated filter package is installed in the case at an angle to the air flow in the form of W-shaped zigzags.

W-form of a filter element is fixed with a reinforced mesh. The filter package itself is placed into a light impact-resistant polymer case.

Pleating and compact laying of the filtering element materially increases the effective area of the filtering material. This improves the dust holding capacity, and therefore the product service life.

W-shaped compact filters are intended for medium and fine water cleaning. They capture fine and aerosol contaminant particles. They serve as the second and third stages of filtration of the air flow that was subjected to rough cleaning.

Most often, compact filters are used:

Filtration classes: М5, М6, F7, F8, F9

NOT subject to regeneration

Highly effective НЕРА filters

НЕРА (High Efficiency Particle Absorbption) filters are highly effective devices for ultrafine cleaning of the air that has already been subject to preliminary (rough and fine) treatment.

The principle of capturing the contaminant microparticles in HEPA filters is fundamentally different from other and arises from the adhesive properties of the filtering material.

A HEPA cassette is a filter package made of ultrasound pleated separated fibre paper hermetically installed into the case profile.

Highly effective filters sterilize the air in the clean premises with the ISO purity classes (GOST ISO 14644-1-2002), ensuring the highest hygienic requirements to the internal space of special areas and working premises for high-precision devices.

HEPA filters are intended for final air cleaning from micro aerosol contaminants of different nature, bacteria, viruses, other microorganisms, radio and nanoparticles.

The “price” of absolute cleaning is quite high aerodynamic resistance of the filter. Their use in household ventilation units is not always reasonable.

The line of absolute filters produced by Research and Production Company MICROSISTEMA LLC includes the following classes: EPA, HEPA, and ULPA.

Regular customers of PHAUF-brand HEPA products include:

Filtration classes: Е10, Е11, Е12, Н13, Н14, U15, U16

NOT subject to regeneration

Filter classes by degree of water cleaning

According to the updated European standard (national analog of GOST R EN 779-2014), the air filters are divided into three main groups by their effectiveness:

Filter class Cleaning degree
G1 Rough
G2 Rough
G3 Rough
G4 Rough
М5 (F5*) Medium
М6 (F6) Medium
F7 Fine
F8 Fine
F9 Fine
Е10 (Н10*) High-efficiency
Е11 (Н11) High-efficiency
Е12 (Н12) High-efficiency
Н13 High-efficiency
Н14 High-efficiency
U15 Ultra low penetration air
U16 Ultra low penetration air
U17 Ultra low penetration air

*- “old” designation of filter class without changes in technical characteristics

Rough cleaning filters

Rough cleaning means capturing from the air flow of the contaminants exceeding 10 ?m in size.

Rough air filters for ventilation systems (G2-G4 classes):

Medium and fine filters

Medium cleaning means capturing the contaminants exceeding 5 ?m in size from the airflow. Medium air filters for ventilation systems (M5-M6 classes):

Fine cleaning means capturing the contaminants exceeding 1 ?m in size from the air flow.

Fine air filters for ventilation systems (F7 – F9 classes):

Highly effective EPA/HEPA filters

Highly-effective (absolute) cleaning means capturing suspended particles of less than 1 ?m from the intake air flow.

Absolute EPA filters (E10-E12 classes) capture up to 85% - 95% of such contaminants.

The effeciency of НЕРА filters (Н13-Н14 class) is measured by the number of nanoparticles with the diameter of 0.1-0.3 ?m that managed to pass through the filter and amounts to 99,995%.

Absolute air filters (classes Е10-Е12-Н13-Н14-U15-U17):

ULPA filters

The air that was cleaned with ultra effective ULPA filters (class U15-17) is almost sterile.

Local value of nanoparticles breakthrough via the filtering element is ?0,0001%. The degree of air cleaning reaches 99,999995% and more.

A major case of using ULPA filters is the air sterilization of pharmaceutical productions, certified according to GMP standard. Local personnel works in special workwear (sterile overalls and overshoes) not to contaminate the air cleaned with absolute ULPA filters.

Types of filtering materials

The effectiveness of an air filter of a certain design largely depends on the used filtering material.

General characteristics of such filtering materials:

Chemical fibre, polyester 100%

The term “100% polyester” implies a large assortment of different brands of chemical (synthetic) filtering materials made from high-quality polyether fibre (sintepon, polyether, lavsan, and PET).

Intended for various designs of air filters of rough and medium purity classes G2-M6.

Meltblown

Polymer textured nonwoven material based on ultrafine polypropylene fibres with the thickness of 1-5 ?m.

Retains good air permeability and excellent filtration properties even at 100% relative air humidity.

Used for manufacturing air filters for medium and fine cleaning of classes M6-F9.

Combined filtering material SMS

Multicomponent filtering material SMS is three-payer composition welded with ultrasound welding by longitudinal and transverse joints. The sticking of pockets is prevented by longitudinal dividers.

The structure of a combined SMS filter fabric by PHAUF:

SMS material is used in fine pocket air filters of M5-F9 classes.

Glass fibre Paint Stop

This filtering glass fibre is formed by fine glass yarn laid in a typical layered structure (each layer displaced relative to another one).

The material in intended for the first stage of air cleaning in significantly dusty environments and capturing liquid aerosol particles (for example, in coating cameras).

Used in rough cleaning panel filters of classes G3-G4.

Fibre paper

Fibre paper is formed by finer combined yarn as compared to the glass fibre.

The material does not absorb moisture and does not lose its filtering abilities in the environments with high air humidity.

Used in fine compact air filters of F7-F9 classes.

Fibre glass with charcoal powder is used in fine charcoal filters capturing micro-aerosol contaminants and smells.

PHAUF Paper made of ultrasound glass fibre

Special filtration fibre paper made of randomly located and tightly laid ultrafine nabofibres of 0.7-6.5 ?m is used for the production of filter packages for absolute HEPA filters.

Frequency of replacement of air filters for ventilation

There are two methods of determining the individual time of replacement of any air filter:

Method No. 1

Based on filter resistance.

It is possible to measure the pressure drop at the inlet and outlet of the air passage using pressure gauges installed at both sides of the filter, or with a differential manometer (differential pressure gauge).

Scheduled filter replacement is performed upon the achievement of the recommended final pressure drop.

Method No. 2

Based on filter service life established by the manufacturer.

In household multistage filter and ventilation systems, the first filter to get contaminated is the filter for the first step of cleaning the outer air (G3-G4). In standard conditions, it is recommended for replacement every three months.

The filter for the second step of cleaning of M5-F7 class is subject to replacement at an average interval from six months to a year depending on the dust burden of the outer air. It is sufficient to replace such a house exhaust filter once a year.

The service life of fine filters of F9 class, as a rule, does not exceed one quarter (3 months).

Filters regeneration after the end of their service life – reasonableness

No air filter, either fabric or glass fibre, may be cleaned, washed, or vacuum-cleaned. Mossy structure of the filtering material after such “cleaning” becomes sticky and loses its filtration qualities. Besides, the captured contaminants cannot be washed out from the mass of the filtering material.

The used filters of ventilation and air-conditioning systems shall be simply replaced with the new ones, which is not hard as they are not expensive.

Panel and cassette filters of G2-G4 classes with a U-shaped profile may be regenerated at the request of the customer by replacing the contaminated filtering fabric with new one of the relevant cleaning class – either by the customer or by a specialist.

Why consumers choose PHAUF filters

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