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Test standards for evaluating filters should provide uniform methods for the quantitative performance evaluation. Currently, automotive air induction filters are tested according to the SAE J726 standard. This standard recommends measurement of the gravimetric initial and final efficiencies. Measurement of gravimetric efficiencies provides limited information on filter behavior, since the information about the size of particles penetrating the filter is not included. In addition, the measurement of the initial gravimetric efficiency does not provide sufficient information on the initial stage of filtration. Determination of the efficiency at the initial stage of filtration is critical, since at this stage filters show their lowest efficiency, which can have an adverse effect on engine wear. To overcome this problem and to obtain more knowledge on the initial stage of filtration, the initial gravimetric efficiency was measured at different levels of dust loading.

The validity of many statistical methods, including statistical process control (SPC) rests on the assumption that the probability distribution is nearly normal. The assumption of normal distribution of variables is not critical in the construction of a confidence interval; however, it is important in constructing a tolerance interval to include a specified proportion of the population. The application of SPC to an industrial process whose variables cannot be described by a normal distribution can be a major source of error and frustration. An assumption of normal distribution for some filter performance characteristics can be unrealistic and these characteristics cannot be adequately described by a normal distribution. A transformation of data can improve the agreement with normality and can greatly extend the range of validity to statistical methods. This paper examines some transformation methods, which can be applied to non-normal distribution.

The performance comparison between different filters requires a test method with repeatable results and low variability. The current SAE J1669 standard does not address some issues related to the measurement of the fractional efficiency of dust loaded filters. This inadequate test procedure can contribute to the unacceptable measurement variability. This paper highlights some of these issues. The influence of media structure, flow rate and amount of dust loading on efficiency measurement is investigated and discussed. The impact of particle shedding on fractional efficiency measurement and variability found to be critical.

The primary purpose of using automotive engine and interior air filtration systems is to reduce the airborne contaminant level entering the engine and passenger compartment. However, the reasons for using such systems are different. The engine air filter should protect the engine from potentially abrasive contaminants causing engine wear. On the other hand, a well designed interior air filter can reduce the concentration of respirable particles, especially allergens, while increasing passenger comfort. The performance of engine and cabin air filters is evaluated by measuring filtration characteristics according to SAE J726 and J1669 standards respectively. To achieve the maximum performance of the filtration system under real conditions, the definition of filter performance must be closely related to the application of the filter. In this paper, standards and filtration characteristics for both applications will be investigated.

The quantification of automotive interior air filter performance can involve several laboratory tests including pressure drop, efficiency, dust holding capacity and a variety of physical properties of the filters. Since cabin air filtration is one of the fastest growing global automotive filter markets, the need for a reliable test procedure has become critical. The SAE J1699 and DIN 71460 test procedures describe the measurement of filter performance characteristics; however, the recommended test stand design, instrumentation and challenge aerosol are not the same. This paper presents the results of an examination of the differences between both standards and their influence on measured filter performance characteristics. The accurate determination of filter performance can be achieved when the sources of test variability are controlled and minimized.

The primary goals of vehicle cabin air filtration are to improve air quality in the passenger compartment, protect the HVAC components from contaminants, and to increase car interior cleanliness. In order to accomplish these goals, cabin air filters must have suitable performance characteristics, including filtration efficiency and pressure drop. Filter performance was measured after operation in two geographical regions. The field test results show that after approximately 24,000 km, filters tested in Arizona trapped over three times more particulate matter than filters tested in Alabama. The pressure drop and efficiency results from filters loaded in a laboratory with various test dusts were compared to the results from the field loaded filters. The comparison showed that filters loaded with SAE Fine dust best reflect the actual pressure drop with both the Alabama and Arizona field tested filters.

In order to be effective in car ventilation applications, an air filter must possess suitable capabilities in each of the following categories: efficiency, pressure drop, dust holding capacity, strength, temperature, humidity and chemical resistance. An evaluation method should provide clear information on the filter characteristics in each of these areas. The most important are pressure drop, dust holding capacity, and gravimetric and fractional efficiencies. They depend on the filter media, air flow, air contaminants and environmental conditions. This paper discusses automotive filter environments in order to understand problems experienced in the field. The influence of several factors involved in car interior air filter performance are evaluated.

Particulate control in car ventilation systems using electrically-charged synthetic filter media are becoming more popular. Adsorption units and low-temperature catalytic systems have been used to control odors and some chemical contaminants in top-of-the-line automobiles. This is a review analyzing these systems, the contaminants found in vehicle environments, and filtration theory. A detailed discussion of experimental work concentrates on overall and fractional filter efficiency and increase in pressure drop with dust loading of charged and uncharged filter media at high aerosol velocity. SAE fine and two natural polydisperse dusts with particles smaller than 5 and 10 μm were used for testing. The health and comfort of car occupants depend on several factors, including air quality. Currently, several car manufacturers offer filtration systems for car interior air.