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New Mercedes-Benz lab procedure shows MB car filters trap even finest allergenic particles

A new testing procedure developed by Mercedes-Benz, for which a patent application has been filed, has shown that even the minutest of allergenic particles are trapped by the charcoal fine particle filters in the vehicle. The results were confirmed by a medical study conducted by ECARF Institute GmbH in an innovative, mobile pollen chamber in the grounds of the Charité university hospital in Berlin.

Allergies are now the commonest form of chronic illness in industrialized countries. In Europe, around 30% of the population is affected. Airborne pollen, emissions given off by materials, or skin contact with them, can lead to a strong immune reaction with symptoms such as swelling of the nasal passages and bronchial tubes or swollen, itching eyes.

Mercedes-Benz already tests numerous interior component for inhalation allergens before the vehicle goes into production. In addition, the pollen filter is tested for correct functioning in both the new and used condition.

From the A- to the S-Class, all Mercedes-Benz model series carry the seal of the European Centre for Allergy Research Foundation (ECARF). The seal confirms that the values measured inside the vehicle meet the Foundation’s stringent requirements and that this has been confirmed in tests.

For many years, we have been testing in all model ranges the efficiency of filters in air conditioners. We design these filters so that, whether in fresh-air or air-recirculation mode, they allow virtually no particulate matter or pollen into the interior of the vehicle. The anti-allergenic effect of our filters in relation to pollen was scientifically confirmed many years ago. Unfortunately, it was previously impossible to measure especially small allergenic particles.

—Dr. Andreas Wiegers, Design for Environment, Interior Emissions at Mercedes-Benz

The minutest particles include fragmented birch pollen, cat hair allergens and molds; these are up to 1 µm in size.

Mercedes-Benz therefore developed a laboratory testing procedure, for which a patent application has been filed. The procedure uses a filtration apparatus with a vacuum suction flask. Small test particles are sucked into a flask through a tube. The flask contains a filter medium—a circular piece approximately 5cm in diameter from the air conditioner filter. The solution is collected in a test tube at the bottom of the suction flask. The efficiency of the filter is measured by means of a before/after comparison, with the concentration of allergens before and after the filter being determined.

“In my opinion, Mercedes-Benz is currently the pioneer when it comes to allergen prevention in vehicles.”
—Professor Dr. med. Dr. h. c. Torsten Zuberbier

In tests with fungus spores, the Mercedes-Benz researchers formed a dilution series and counted the number of spores in a Petri dish. In the case of cat hair epitheliums and fine particles, the concentration of allergens was determined as the average outgoing quality in the ELISA test (Enzyme Linked Immunosorbent Assay). Depending on the concentration of allergens, the color reaction of a liquid differs in intensity.

The outcome of the laboratory tests is that the fine particle filter in Mercedes-Benz vehicles traps even the minutest of allergenic particles.

The separation rate is over 95 percent. This means that the filters meet our target straight off.

—Dr. Andreas Wiegers

The activated charcoal fine particle filter (standard in the S-Class, optionally available in many model series) offers optimal filtering of the outside and inside air; the activated charcoal also keeps odors out of the interior. The AIR-BALANCE package is optionally available for fragrancing the vehicle interior to suit personal taste. A choice of four interior fragrances is available to suit personal preference and mood. The air quality can also be improved by ionization.

ECARF study. A medical study conducted by ECARF Institute GmbH with asthmatics as test subjects has confirmed the anti-allergenic effect of the filters. The tests were carried out using a section of the air conditioner from the current S-Class in the mobile pollen chamber in the grounds of the Charité university hospital in Berlin.

The mobile pollen chamber ranks as a milestone in allergy research. This is because, in a field study, which involves the patients keeping a daily diary at home, the medical experts cannot be sure whether the test subjects have really been exposed to the allergen. On the other hand, large, fixed exposure chambers do not allow multicentre studies with different patient types and a cross-section of the population. A modern exposure chamber makes it possible to conduct tests with a multiplicity of different aero-allergens and various patient types.

The mobile pollen chamber is made up of two large standard containers, which are joined together and can be easily loaded and off-loaded. This makes it possible to conduct medical studies in any location.

—Professor Dr. med. Dr. h. c. Torsten Zuberbier, Head of ECARF

The scientists sit in one of the two containers and monitor the tests. The second container is the actual chamber, which has seats for the test subjects. Above each seat is an outlet, through which the pollen particles are released, laser-counted, through an air cone. Inside the chamber, it is possible to individually select for each test subject whether the air stream contains pollen or not. This also allows for placebo testing. Every ten minutes, the test subjects make a note of any complaints on a standardized symptom sheet. In addition, there is intermittent testing of pulmonary and nasal function as well as monitoring of eye reddening.

Interior emissions: extensive testing of many components and all cars. Mercedes-Benz has numerous experts in development and materials technology who work on the interior air quality in new models. Even in the early stages of the development of a vehicle, up to six years before it goes into production, the minimization of interior emissions is a factor helping to define the materials concept.

In December 2015, Mercedes-Benz opened a new test chamber for interior emissions at the Mercedes‑Benz Technology Centre in Sindelfingen. In this chamber, which has a volume of almost 300 cubic metres, a vehicle runs through precisely defined temperature profiles in the course of a week and is tested for several hundred substances. In several cycles, more than 100 air samples are taken from the vehicle interior and analyzed in special laboratories. In addition to the overall emissions, it is also possible to measure the emissions of individual organic compounds.

Mercedes-Benz has conducted such analyses since 1992. Component assessment involves the testing of numerous parts from each trim variant of a model series—door panels and seats as well as the roof liner and trim. In order to ensure that a realistic impression is gained, the team do not use specially produced sample components, but standard production components made using the tools that will be subsequently used for series production.

The testing procedure requires adherence to the VDA 276 standard as laid down by the German Motor Industry Association—the components are stored and measured in a test chamber 1 m3 in size at a defined temperature, humidity level and air circulation rate. Air samples are then extracted and used to measure the quality and quantity of gaseous substances in the air.

The examination of the vehicle as a whole involves an even more complex process. The preparation of the vehicle alone—i.e., the installation of the measuring equipment—takes three quarters of an hour, while the measurements themselves last a full week. The test chamber is lined with stainless steel in order to prevent it giving off emissions of it own. Large radiant heaters are used to simulate the sun and heat up the interior of the vehicle, since, for physical reasons, emissions are greater under the influence of heat. The solar irradiance is measured by special devices called pyranometers.

Inside the vehicle, as many as ten sensors are used to record the temperature in various areas, for example on the top of the dashboard. A rotating paddle stirs up the air inside the vehicle to ensure an even mix. Overall emissions within the vehicle are calculated with the help of a rack-mounted flame ionisation detector. The rack projects into the vehicle interior over the opened window on the driver’s side, which has been made airtight and emission-neutral with the aid of aluminium foil.

If taking measurements according to test method FAT AK 26, for example, measuring can begin as soon as a temperature of 65 ˚C has been reached at the level of the driver’s nose. Samples of air are extracted from the interior and the air flow directed into a series of test tubes. The chemical composition of the evaporated substances is then analyzed in the laboratory.

ECARF seal: extensive allergen testing. All model series from the A- to the S-Class meet the criteria of the ECARF seal for allergy-friendly car interiors. The requirements are extensive: for instance, the air from several trim variants of a vehicle is tested for inhalation allergens. In addition, the pollen filter is tested for correct functioning in both the new and used condition.

There are also tests on test subjects, which are approved in advance by the Ethics Committee of the Charité university hospital in Berlin, the seat of ECARF. Driving tests, for example, were conducted with people suffering from severe asthma, with pulmonary function tests providing information about the impact on the bronchial system.

In addition, all materials that might come in contact with the skin were dermatologically tested. What are known as epicutaneous skin tests were undertaken with test subjects suffering from contact allergies in order to test the tolerance levels for known contact allergens such as chrome-nickel and various pigments. This involved substances from the interior that were deemed to be potential allergens being applied with plasters to the skin for 72 hours and the reaction to them being evaluated after 48 and then 72 hours.


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