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The gravimetric method is commonly used in engine air filtration technology for air cleaner, filter element and filter media testing. An “absolute” filter is employed in-line to collect any dust particles passing through the test filter. Air filter efficiency is calculated by comparing the mass of dust collected by the test filter with that fed to the filter. This method measures only the mass of dust penetrating the filter. It does not provide information on contaminant particle size. Moreover, this method, in many cases, has inadequate precision to distinguish between filters. Both the dust mass and its particle size are needed to estimate engine wear. Therefore, the SAE J726 Air Cleaner Committee initiated work on a test method to measure engine air cleaner fractional efficiency. This paper discusses problems associated with development of the fractional efficiency method for engine air cleaners.

The development of a particulate filter for a motor vehicle ventilation system is based on filter performance requirements, vehicle's operational environment, available space, filter media properties, and filter element technology. The design process includes analyses of theoretical and empirical models describing filter media performance and aerosol flow in filter housings and through filter elements. Filter media are carefully selected based upon these models and simplified laboratory tests. The filter element design is evaluated in great detail through a series of laboratory and field experiments. This paper shows the process of cabin filter design, including filter media selection and experimental evaluation. Four recently published ISO and SAE test methods are discussed in detail. One of them, the SAE J1669 test procedure, was used to determine full scale filter element performance characteristics.

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.

A test method employing a Continuous Aerosol Monitoring (CAM) system was developed to determine air filter performance. Overall and fractional filter efficiency and pressure drop can all be obtained as a function of time, dust loading, or dust particle size. The on-line CAM system simultaneously analyzes the concentration and size distribution of the dust upstream and downstream of the test filter. A MicroVAX computer is used to analyze the data. The overall filter efficiency determined by the CAM system is comparable to that obtained using the gravimetric method.