Ventilation systems must be equipped with filters. There are many varieties of them. They differ in the degree of purification, design, filter material, as well as the principle of operation. On the variety of types of filters for ventilation and the intricacies of choice, read on.
Purpose of ventilation filters
In the supply ventilation system, a filter is necessary to purify atmospheric air before being fed into the room. The air of modern cities contains dust, car exhausts, pollen and plant fluff. Therefore, ventilation grilles with filters are installed.
Filters for ventilation systems in production halls are even more important.
Unlike charcoal filters for supply ventilation, the systems of plants and factories use a wide variety of fillers and designs.
Many processes occur with the release of wood or metal dust, harmful or fetid gases. The release of impurities into the atmosphere would threaten an environmental disaster. Therefore, exhaust ventilation of industrial enterprises is necessarily equipped with filters.
Principle of operation of ventilation filters
Various types of filters trap impurities from the air on their surface or absorb them.
On this basis, they can be divided into:
- porous;
- bulk (absorbing);
- tissue.
The most common representatives of the bulk category are charcoal filters for fresh air ventilation, they are effective and inexpensive. In addition to activated carbon, the smallest crumb of rubber, gravel, metal shavings, ceramic particles, and coke can be used.
The materials for ventilation filters of the porous category can be finely perforated metal sheets, synthetic nets, non-woven materials.
Fabric filters can be classified as porous, they are made from natural fibers: cotton, wool.
Degrees of cleaning of ventilation filters
There are three classes of ventilation filters according to the degree of purification:
- First class or absolute cleanup: particles less than 0.1 microns are retained. They are installed in electronic industries, in operating rooms and other sterile rooms, as well as for protection against radioactive dust and aerosol impurities;
- Second class or fine cleaning: particles of 1 - 10 microns are captured. Their effectiveness is 60-95%, they are installed in laboratories, clinics, pharmaceutical and food factories;
- Third grade or rough cleaning: particles larger than 10 microns are captured. Efficiency up to 90%. Used as a preliminary cleaning in very dusty rooms.
Often there is a need to install a number of ventilation filters of various classes that gradually clean the air. Otherwise, with high dust content, the absolute filter quickly clogs and fails.
Replaceable cartridges with material for ventilation filters are provided for fine cleaning. Therefore, you can save on changing expensive consumables by pre-cleaning the air mass with lower-class ventilation filters.
Types and designs of ventilation filters
The following types of filters are installed in the supply and exhaust ventilation systems:
- Roll. The material for ventilation filters is most often polyester. The thicker the roll, the higher the filter cleaning class.
- Cellular They are divided into two categories:
- Cassette ventilation filters. Good for almost any ventilation system with rectangular ducts, so it is very widely used. Cassette ventilation filters are installed in factories, in public buildings or in residential buildings. Cassette ventilation filters perform a rough air purification;
- Pocket ventilation filters or bag filters. Coarse dust is deposited very effectively, therefore it is often used as the primary stage of rough cleaning. But there are varieties with fabrics for ventilation filters made of polyester, polypropylene or polyethylene fibers that provide EU5-EU classes. Then pocket ventilation filters can be used as the only cleaning device. They withstand up to 220 degrees Celsius and have a high dust capacity (up to 300 g / sq. Cm).
- Channel. Duct charcoal filters for ventilation are good because they can be integrated into any section of the duct of an already installed system. In addition to the ability to pick up dust and stench, the channel carbon filter in ventilation drowns out sounds very noticeably. Therefore, it is often installed after the fan as a silencer.
- Electrostatic or electrical. They clean the air of production halls from the smallest particles of paint, oils, and solid materials. Due to the action of electrostatic fields, particles approach the surface and are held on it. They need timely cleaning, otherwise the filter efficiency decreases sharply.
- Panel filters for ventilation. Suitable for exhaust, supply systems, including with the reuse of air. Simple enough and effective. Panel filters for ventilation are a metal lattice base framed by a mesh. Filter material is laid on it, the density of which is determined by the class of ventilation. Panel filters for ventilation are produced with a profile width of 25 to 96 mm.
- Self-cleaning. Widely used in industry where it is impossible to stop the technological cycle for cleaning or changing filter cloth in ventilation.
- Aerosol. Installed in hazardous industries (chemical and nuclear power). Captures dust, microorganisms and harmful chemical impurities, makes the exhaust air perfectly clean.
- High temperature. It can be distinguished into a special category, although pocket filters for ventilation, and any other structures can also be high-temperature. They are installed in saunas, baths, wood dryers. All housing elements and the filter module are made of materials that can withstand temperatures up to +300 degrees, without deforming and without reducing efficiency.
- Bactericidal. Another category of highly specialized equipment is bactericidal ventilation filters. They are installed on the inflow and recirculation of air masses. Before entering the room, the air is completely cleaned of germs, passing through a stream of ultraviolet radiation. Antibacterial filters for ventilation correspond to class H11. They delay life-threatening microbes, viruses, bacteria, mold spores and fungi, and a special impregnation destroys them. The effectiveness of antibacterial ventilation filters is more than 95%. Bactericidal filters are always installed in the ventilation of laboratories, hospitals, clinics, clean production facilities.
- Grease traps. Grease filters for ventilation are in the form of cartridges. They are a filter cloth fixed on a frame made of galvanized profile. Grease filters are installed in the ventilation of catering enterprises directly in exhaust hoods above the hobs.
As a filtering cloth for ventilation, a expanded metal mesh of 5-7 layers with a mesh of 0.35 x 0.6 cm is used.The grease filter for ventilation can be washed by pre-soaking in hot water with a detergent.
Filter materials in ventilation filters
The class of air cleaning in the ventilation system depends on the characteristics of the filter material. Often, to obtain the best effect, several filter modules of various classes are combined.
The separation of large suspensions occurs using:
- metal mesh;
- nonwoven materials (synthetic winterizer, felt);
- fabrics (cotton, flannel, linen, wool);
- paper;
- fiberglass.
In industry, the feature of fiber filters is widely used to precipitate chemical fog (fine suspension of paints, oils, and other chemicals).
Wire Mesh Filters
Able to retain impurities with a particle size of at least 5 microns. That is, metal filters provide preliminary rough cleaning. To make the mesh better “collect” dirt, its surface is sometimes covered with a layer of engine oil. Filters can be cleaned independently: the tape is passed through a container with oil, where the dirt is washed off.
Oil ventilating filter grilles filter out more than 90% of impurities from the air and are able to work with dust content up to 25 mg / cubic meter.
Water filters
There are water filters that are installed in restaurants above sources of open fire (for example, barbecue).
A water filter precipitates impurities and cools the exhaust air to 38 - 40 degrees before releasing it into the atmosphere.
Carbon filters
This material captures volatile as well as semi-volatile organic compounds more effectively than others. Therefore, channel carbon filters for ventilation are used to absorb relatively "heavy" molecules. Microscopic pores give this property to coal, and the degree of air purification depends on their quantity. The more pores, the cleaner the air will escape after the filter.
Another important indicator of channel carbon filters for ventilation is the size of the granules. Large granules are less resistant to air flow than small ones.
Charcoal filters are rarely used for pre-cleaning in fresh air ventilation systems, because they quickly clog and fail.
Sintepon filter mats
The basis for the production of filter mats is a synthetic fiber similar to sintepon. Ventilation filters are equipped with mats of different thicknesses and with different degrees of cleaning: from EU2 to EU6.
Ventilation filters from sintepon withstand temperatures up to +80 degrees, are not affected by moisture.
Sintepon filters are provided for ventilation of rooms with a high dust load and for the first stage of filtration in paint and varnish installations.
They are made in the form of ventilation grilles with a sintepon filter or in the form of a sleeve.
Fiberglass Filter Mats
Any fiberglass filters have cleaning classes EU2-EU4. Depending on the variety used:
- in paint or varnishing installations;
- in furniture production;
- in the automotive industry.
Bactericidal ventilation filters are made from fiberglass. The antibacterial effect is achieved by additional coating of the surface of the fiberglass material with special compounds that repel dust and destroy microbes. Bactericidal glass fiber ventilation filters are usually yellow.
They withstand up to 200 degrees Celsius, are not affected by moisture.
Filter mats are sold in rolls. And fiberglass can be ordered to the required size. The filter material for ventilation is framed with a metal corner and reinforced with a cloth.
Short video review of HEPA filters for fine air filtration:
