Climate Control Exhaust Gas Sensor: Description and Operation
Air quality sensor
To offer the customer a passenger compartment which is free of bad odours and pollutants.
By placing an air quality sensor in the air intake it is possible to measure the amounts of polluted air, primarily from motor vehicles. The signal from the
air quality sensor is used to exclude the pollutants by using the recirculation (REC) mode. An activated carbon filter is installed in the heater. This filter
takes care of the pollutants in the couple of seconds before the recirculation shutter closes and on those occasions when recirculation cannot be used
because of misting. The filter and the sensor are interdependent to provide the customer with as clean a passenger compartment as possible. The climate
control system is equipped with a button to activate the system.
By supplying a particle filter with activated carbon, gases entering the passenger compartment can be absorbed. The focus of exclusion is on the
following substances: NO, NO2, HC(benzene, toluene, xylene), CO, ozone.
What can activated carbon absorb?
Cold start: Good absorption of petrol components is usually achieved.
Manure: Ammonia is badly absorbed, however some neutralization can be expected.
Exhausts: Good separation of uncombusted hydrocarbons and "diesel odour" is achieved.
Oil odour: Good.
Water treatment plants: Sulphuric acid cannot be dealt with.
Pulp mills: Many odorous substances. Some can be absorbed.
Odours are complicated and are difficult to explain in terms of concentrations and percentages. A filter will reduce odours and minimize strong odour
changes and will therefore improve comfort. The car can never be completely odourless. In some cases the odour compounds may seem unexpected
because the constituent substance compounds are modified.
The sensor registers NOxCO and HC. These are the most prominent compounds produced by motor vehicles. The sensor registers increases in
concentrations, for example when a tunnel is entered or when driving behind a truck. The sensor learns the environment it is in and only reacts to the
relevant increase in concentration. One point is that the sensor reacts to CO, a compound which activated charcoal filters cannot handle.