STUTTGART, Germany –—- Mercedes-Benz has been awarded the Seal of Quality of the European Centre for Allergy Research Foundation (ECARF) for its passenger cars. This makes Mercedes-Benz the only vehicle manufacturer to bear this seal. The ECARF Seal of Quality is used by ECARF to designate products that have been scientifically tested and proven to be allergy-friendly. Alongside comprehensive testing for inhaled and contact allergens, Mercedes-Benz has been testing the interior emissions of all its model series for 22 years now. And a team of olfactory experts works to ensure that odours in Mercedes-Benz vehicles remain at a consistently pleasant level.
“We are delighted that the allergy-friendly nature of our Mercedes-Benz passenger cars has now been scientifically and independently recognised through the award of the ECARF Seal,” commented Dr Jörg Breuer, Director Certification, Regulatory Affairs & Environment at Daimler AG. “Indeed, the constant improvement of air quality in the interior has for many years now been a key aspect of the development of components and materials for Mercedes-Benz vehicles.”
“In our estimation, Mercedes-Benz currently represents the benchmark in terms of allergen optimisation for vehicles,” according to Professor Dr Torsten Zuberbier, Director of the European Centre for Allergy Research Foundation (ECARF), which is based at the Charité university hospital in Berlin.
The new C-Class is the latest Mercedes-Benz model to have received the ECARF Seal of Quality. The conditions of certification have been met by all model series launched in recent years, from the A-Class to the S-Class. The criteria behind the ECARF Seal are also included in the specifications book for all future Mercedes-Benz passenger car model series.
The emphasis on clean air applies for Mercedes-Benz in three particular areas: along with the avoidance of allergens, the concern is to reduce interior emissions and to keep odours at a consistently pleasant level.
“We have been measuring the interior emissions of our vehicles since 1992 and have been able to make steady progress in reducing them,” according to Dr Breuer. “We have a strict internal limit these days, which has to be met by all Mercedes-Benz passenger cars – by our compact vehicles and roadsters but equally by our large estates and SUV models.”
There are currently a dozen or more experts working in the development and materials technology area on the interior air quality of new models. Over the course of the coming year, the team will also be moving into a new test centre at the Mercedes-Benz Technology Centre in Sindelfingen – a fact which also serves to emphasise the importance given to this topic.
Even in the early stages of the development of a vehicle, up to six years before it goes into production, the minimisation of interior emissions is a factor helping to define the materials concept. As far back as 1996, Mercedes-Benz’s own internal standards set emission levels for materials used for components in the passenger compartment and boot. Today designers and developers can make their choice from a database of around 8000 interior materials that have been approved by the specialist department.
Interior emissions: extensive testing of many components and all cars
Just before a new model goes into series production, its interior emissions are tested in a series of complex procedures. This type of analysis has been conducted by Mercedes-Benz since 1992. Component assessment involves the testing of numerous parts from each equipment 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 produced using the tools that will be subsequently used for series production. The testing procedure prescribes 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 necessary preparation of the vehicle alone, in other words the installation of the measuring equipment, takes the well-rehearsed team 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 its 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 degrees Celsius 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 analysed in the laboratory.
“We use different sampling techniques for the various categories of substance that we analyse,” explains Hartmut Kovacs, Design for Environment, Head of Interior Emissions at Mercedes-Benz. “All in all, we take more than 100 samples from each vehicle.” As well as the overall emissions, it is therefore also possible to measure the emissions of individual organic compounds.
The emissions experts also look at a vehicle’s propensity to fogging – in other words the creation of a film of condensable substances on a car’s windscreen: the measuring rack therefore also includes a cooled sheet of glass upon which these less volatile substances, if present, are deposited.
In addition to this static test, a further series of tests are used to evaluate emission activity in the interior of the vehicle while it is in use. These tests take place with the engine running and the air-conditioning system switched on, with and without air recirculation. A further touch involves the driver’s door being opened once during each measurement cycle to simulate the driver getting into the vehicle.
ECARF Seal: extensive allergen testing
“In our estimation, Mercedes-Benz currently represents the benchmark in terms of allergen optimisation for vehicles,” according to Professor Dr Torsten Zuberbier, Director of the European Centre for Allergy Research Foundation (ECARF), which is based at the Charité university hospital in Berlin. In industrialised countries these days, allergic conditions are now the most common form of chronic illness. In Germany, for example, around 30 percent of the population are affected. One in ten absences from work as a result of sickness is now attributable to an allergy.
But the pollen count is not the only problem to afflict motorists who suffer from allergies: emissions given off by the materials used in the interior or when contact surfaces are touched can also lead to a strong reaction, with symptoms such as swelling and inflammation of the nasal passage, hay fever or asthma.
But not in a Mercedes-Benz vehicle: numerous model series, from the A-Class to the S-Class and now also the C-Class, meet the criteria of the allergy label. The conditions involved are extensive: numerous components from each equipment variant of a vehicle have to be tested for inhaled allergens, for example. Furthermore, the function of the pollen filter must be tested in both new and used condition.
And then there are tests with human “guinea pigs”. Driving tests, for example, were conducted with people suffering from severe asthma, with lung 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. So-called 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.
The air-conditioning filters also have to meet the stringent criteria of the ECARF Seal in both new and used condition: amongst other things the tests measure their retention efficiency with regard to dust and pollen.
The professional sniffers: tracking down pleasant smells
Ultimately responsible for ensuring that odour levels in Mercedes-Benz vehicles remain consistently pleasant is a team of olfactory experts. Mercedes-Benz has carried out an odour test since 1992. The olfactory experts take a sample of every single material that is to be used inside a new vehicle. They place this sample in a standard, odour-free preserving jar, which is then sealed and heated for two hours at 80 degrees Celsius. This is the temperature that can be reached inside a car if it is left in the blazing sun. And it is a fact of physics that odours become stronger under the influence of heat. The testers than allow the jars to cool down to 60 degrees, ready for the “sniffing” to begin.
Each tester lifts the lid up slightly, smells the air inside the jar and writes down a mark for the strength and quality of the smell. The final result represents the mean value of all the marks. The assessment scale corresponds to the German school grades system, i.e. from one to six. A grade-one odour is “imperceptible” (for example glass, metals, stones), while three indicates an “obvious and distinctive smell, but not unpleasant” and six is “unbearable”. Everything in the grade range from one to three passes the test. Materials that fare worse cannot be used in the vehicle. It’s then up to the supplier to make improvements. If the material passes a re-test, that test result becomes mandatory.
In order to test the odour produced by the interaction of all the various materials, the experts quite literally stick their noses into the finished vehicle before it goes into series production. Four of them jump in, close the doors and have a good sniff. The odour team also carry out an olfactometric test. For this, the interior of the vehicle – with all its doors and windows closed – is warmed up by large heaters. Using a bag, the specialists take an odour sample of the ambient air inside the closed vehicle. This bag is then attached to an olfactometer, a special device for measuring smells, and diluted with pure, odourless air before being smelt by a group of test subjects.
New C-Class: Climate control system uses signals from space
A significant factor in the excellent air quality found in the interior of the new C-Class is the further developed climate control system. The two-zone automatic climate control has separate settings for the left and right, THERMOTRONIC a further setting for the rear. However, instead of channelling the air to the rear via an air duct as is customary, it has its own blower in the centre console. This lets rear-seat passengers set their own feel-good climate.
The THERMOTRONIC three-zone automatic climate control is optionally available, the only real such system in this segment. In addition to separate controls for the driver and front passenger, it provides the option of setting the temperature and air flow in the rear compartment. It also offers a choice of three ventilation modes: Medium, Focus, Diffuse. In addition the system is equipped with a pollutant sensor that switches automatically to air recirculation mode – particularly useful, for example, when caught in a traffic tailback alongside trucks.
The new C-Class is the only vehicle in the segment to offer tunnel detection via satellite navigation. On the basis of map information from the navigation system and the GPS location data, the system detects when the vehicle enters a tunnel. It then automatically closes the air recirculation flap in order to prevent the exterior fume-filled air from entering the vehicle via the air vents. Once the vehicle has left the tunnel, the flap opens and fresh air can once again flow into the interior.
Another highlight for creating the feel-good atmosphere is the AIR-BALANCE package with active fragrancing, ionisation and even more efficient filtration compared with the standard model. It was adopted from the S-Class, in which the AIR-BALANCE package only recently celebrated its world premiere. The various fragrances available have been specifically developed for this purpose and, like the ionisation and filtration functions, tested by ECARF for their acceptability to allergy sufferers.
Ionisation is another component of the AIR-BALANCE package, with which the air from the air conditioning is conducted into the interior via the ioniser. The ioniser generates oxygen ions by means of high voltage. The air ionised in this way can eliminate certain viruses, bacteria and spores. At the same time the air can be freshened by an increased concentration of negatively charged oxygen ions. Both help to increase the well-being of passengers. In tests undertaken with asthmatics, under the supervision of Professor Zuberbier, the test subjects reported a clear improvement in their well-being as a result of the ionisation process.