Emissions from motor vehicles are generally recognized to pollute the outside
air, with negative effects on human health and the environment. Little is known
about the extent to which these pollutants enter the interior of the vehicles
through their ventilation systems. The cabin air quality inside vehicles is very
lightly regulated around the world, and there is no recognized standard method
for measuring pollution ingress. This article tests the effectiveness of a
method originally proposed in an SAE paper in 2019 for characterizing the degree
of particle ingress. This cabin air quality index is hypothesized to give a
repeatable, characteristic value for the vehicle to reduce in-cabin pollutant
concentration compared to outside pollutant concentration, which may be suitable
for inter-vehicle comparison.
To test the method, a series of real-world on-road tests were conducted in
Germany with three different types of measurement equipment, two different
drivers, and two different routes, with a view to quantifying the repeatability
and reproducibility of measurements. The methodology used was based on a draft
test protocol being developed by the standardization organization, the Comité
Européen de Normalisation (CEN), and its Workshop 103.
The results showed strong levels of repeatability and reproducibility regardless
of the route and the driver. The cabin air quality indices were different
between different particle metrics, reflecting size-dependent filtration
efficiency and different mode diameter for different metrics for the same
particle size distribution, but there was high consistency within measurements
from the device measuring the same metric.
The conclusion is that the method proposed in 2019 is a suitable method for
deriving characteristic cabin air quality values for vehicles, which could then
be used for comparison or regulation.
