PARTICULATES AND THE IMPORTANCE OF CAR INTERIOR AIR FILTERS
The air we breathe contains several particulates that are often noxious for our health.
On the roads, the concentration of particulates is remarkably higher: let us only mention the wear of tyres, the dust shifted from the wind and the passing of vehicles, exhaust gases and the wear of braking materials.
Besides that, let us consider natural elements, too, such as pollens, dirt, etc., that are surely less noxious for health but represent a source of allergies.
Particulates are generally subdivided into classes according to their size, the most known being PM10 and PM2.5
The ventilation system of our car can be compared with a vacuum cleaner!
It "sucks" the air rich in polluting particulates from outside the car and after having treated it thermally, "throws" it in the driver’s cabin.
The only barrier between the air from outside and our lungs is a filter that just for this reason is called CAR INTERIOR AIR FILTER!
Now, you can better understand how it is really important and necessary to use and replace a quality Car Interior Air Filter.
CAR INTERIOR AIR FILTERS
Two main types of car interior air filters are available:
- PARTICULATE FILTERS, characterized from their effect against dusts or particulates
- ACTIVE CARBON FILTERS, active against dusts and gaseous pollutants.
The difference between these two kinds of filter lies in the material used!
All the filtering materials used from Campi are tested according to the Standard EN779 and belong to the High-Efficiency class (see Standards).
All the filters are tested for mechanical efficiency as provided for from the Standard in order to assure efficiency levels with the passing of time.
The particulate material is made of interwoven polyester fibres. It is a synthetic medium that does naturally not offer fertile soil to bacterial strains and molds.
ACTIVE CARBON FILTERS
Active carbon is an adsorbing material. To exercise this function, it exploits its huge surface. Just think that one gram carbon has a surface of 500 to 3000 sq.m.: indeed, active carbon is made of thousands of tunnels!
Active Carbon acts through a Physical or Chemical principle of operation:
- Physical principle: the pollutant material deposits while passing through the "tunnels"
- Chemical principle: by licking the carbon surface and because of Van Der Waalls forces, the airflow deposits the suspended molecules creating molecular bonds.
It has to be specified that air speed plays an important role; an excessive speed is prejudicial to the efficiency of the filter.
For the purposes of knowledge, active carbon can be of Synthetic, Mineral and Vegetable nature.
According to its nature, active carbon has different porosity and pore diameter. It is important to assess this parameter in consideration of the substance to be filtered.
In the specific case of gaseous material, vegetable active carbon is generally used, mainly drawn from the shell of coconuts.
Our filtering material is made like a “sandwich”. The first layer is made of a synthetic filtering tissue that is extremely effective against particulates. On this layer, another layer is positioned made of active carbon granules with which a synthetic restraint tissue is then coupled.
Why do we sometimes still perceive odors?
- Active carbons are effective on some pollutants, only! - The concentration of the pollutant and air crossing speed are important. - Active carbon might be completely saturated.
STRUCTURE OF THE FILTER
You must not believe that quality and efficiency of the material are the only ingredients of a good filter. Structure is equally important to assure the tightness of the filter as well as its efficiency.
Unfortunately, it could often be observed on the market that structural "cuts" had been done to reduce costs.
Sometimes the filter-bearer is designed to activate a front hold in the filter. In this case, the filtering cartridge can simply be made of the pleated filtering material and of lateral edges. In this case, the filtering cartridge can simply be made of the pleated filtering material and of lateral edges.
In many cases, the filter has to be tightened on the perimeter of the cartridge and therefore we install stiffening supports on the filter heads that assure better tightness.
In other cases, a gasket is absolutely necessary.
In order to achieve the best results, we arranged several types of tightness according to the characteristics of the filter case.
In order to achieve the best results, we arranged several types of tightness according to the characteristics of the filter case. A medium was developed able to grant tightness without particular friction resistance.
FLEXIBLE EDGES This filter was designed to be replaced in the most uncomfortable conditions granting lateral tightness without excessive friction
REINFORCED STRUCTURE it assures the filter tightness in position. If needed reinforcements and gaskets with low friction coefficient and high tightness are added.
REGULATIONS ABOUT FILTERING
Several regulations exist to classify filters and their efficiency. When we started our activity, Eurovent regulations were in force: they classified efficiency but did not consider capacity.
In 1993 the European commission published the standard EN779, about Anti-dust Air Filters for general ventilation systems. It got the idea from Eurovent and from the American Ashrae 52-58. At the beginning, this regulation considered the average efficiency, only.
A classification system was thus provided that adopted methods fit for comparing similar products but not for showing their evolution in time.
In 2002, the standard EN779 was modifiedintroducing a series of tests, too, fit for setting the evolution of the filter in time, i.e. measuring its efficiency and loss of load both when it was new and when it was clogged.
The size of the reference particulate is 0.4 micron.
In 2012, the Standard was changed again to consider the electrostatic charge of the filter, too.
Actually, the filter has to be tested without electrostatic charge, too. The initial efficiency of an electrostatically charged filter may significantly worsen when it loses its charge.
Therefore, the filter is “discharged” by being treated with different substances, such as Isopropanol, Diesel Smokes, detergents or sulphates in water.
Diesel smokes are excellent dischargers and simulate very well the real long-lasting performance.
Just for the discharging effect of diesel smokes, our products are always assessed for their mechanical efficiency!
In 2018, EN779 will be replaced from ISO16890, an international classification system.
EN779 classifies the filters according to the filtering degree and gives us indications about what we intend to filter with said given material.
Filters are subdivided into three main groups:
- Anti-dust Filters – High-efficiency Filters – Absolute Filters
Anti-dust filters are effective on particulates of significant sizes, greater than 10 micron.
High-efficiency filters significantly absorb particulates between 10 micron and 1 micron.
Absolute filters are significantly effective on particulates smaller than 1 micron.
Why can more efficient materials not be used for car interior air filters?
Too efficient materials lead to a loss of load, i.e. they stop the airflow.
In mechanical filtering, efficiency, i.e. the ability to absorb ever thinner particulates, is directly proportionate to the loss of load.
Thus, as said before, too high levels of efficiency lead to an excessive loss of load.
Unfortunately, the reduced size of many filters does not allow using these materials and, finally yet importantly, costs would increase too much.