Air Quality in Passenger Cabins

Overhead panel of an airplane cabin showing air vents, light controls, and a call button for passenger comfort and convenience.

We spend up to 90% of our time indoors. This includes passenger cabins of vehicles like cars and aircrafts. Often space is limited which can impact air quality negatively.

If nothing else, the recent pandemic has risen awareness for CO₂ levels in our meeting rooms, passenger cabins and classrooms. When CO₂ levels increase, so does the concentration of other particles and also viruses in the air. This can quickly become a problem, especially in places that offer limited space for large numbers of people. Monitoring the air quality in passenger compartments is therefore not only essential for our health: Poor air quality also affects our well-being and can lead to headaches and lack of concentration. This is particularly problematic for drivers of motor vehicles and poses safety risks.

CO₂ as an Indicator for Air Quality

Air quality can deteriorate rapidly in crowded public transport vehicles at rush hour. In buses this is often not so critical as the doors can be opened at every stop and thus ensure a regular exchange of air.

Interior of a panoramic train car with large windows and glass roof, offering scenic views of forests and comfortable seating for passengers.

In trains, however, this is not so simple; here, air quality must be controlled primarily via the air conditioning system. If this control system does not function reliably, the CO₂ levels in the cabins can quickly rise to well over 1000 ppm or a multiple thereof. The value of 1000 ppm CO₂ indicates that about 1.5% of the air we breathe in has previously been in the lungs of another person. With higher CO₂ values, this proportion increases exponentially. Precise measurement technology is needed to check levels reliably. Non-dispersive infrared spectroscopy (NDIR) has proven to be very well established for CO₂ measurements. The infrared sources from Axetris have a particularly high emissivity at the wavelength of 4.26 µm relevant for CO₂, which makes them perfectly suited for this application.

Stop and Go - a No-Go for the Environment and Motorists

Air quality in road traffic is even more critical. It is not surprising that the pollution levels on busy roads are extremely high.

A driver’s perspective shows hands on the wheel in heavy city traffic at sunset, with dashboard instruments and infotainment system visible.

Even in the vehicle itself, the levels of nitrogen oxides, for example, can be dangerously high. Especially in city traffic, vehicles are often standing close together. As a result, the exhaust gases from the vehicle in front enter directly into the vehicle's own ventilation system and thus into the vehicle interior. Tests conducted in Germany show pollution inside the vehicle up to twice the levels outside. The toxic gases also come from the car itself. For example, up to 50 different volatile organic compounds (VOCs) have been detected in new cars, some of which were found in concentrations that were harmful to health. Reliable measurement technology for monitoring air quality in vehicle interiors is therefore essential.