Aims: To evaluate the real-life effect of photocatalytic surfaces on the air quality at two
test-sites in Denmark.
Background: Poor air quality is today one of the largest environmental issues, due to the adverse
effects on human health associated with high levels of air pollution, including respiratory issues,
cardiovascular disease (CVD), and lung cancer. NOx removal by TiO2 based photocatalysis is a tool
to improve air quality locally in areas where people are exposed.
Objective: To demonstrate and quantify the NOx removal capacity of photocatalytic asphalt and
concrete in real life.
Methods: Two test sites were constructed in Roskilde and Copenhagen airport. In Roskilde, the
existing asphalt at two parking lots was treated with TiO2 containing liquid and an in-situ ISO 22197-
1 test setup was developed to enable in-situ evaluation of the activity of the asphalt. In CPH airport,
photocatalytic concrete tiles were installed at the "kiss and fly" parking lot, and NOx levels were
continuously monitored in 0.5 m by CLD at the active site and a comparable reference site before and
after installation for a period of 2 years.
Results: The Roskilde showed high stability of the photocatalytic coating with the activity being
largely unchanged over a period of 2 years. The CPH airport study showed that the average NOx
levels were decreased by 12 % comparing the before and after NOx concentrations at the active and
Conclusion: The joined results of the two Danish demonstration projects illustrate the high stability of
the photocatalytic coating as well as a high potential for improvements in the real-life air quality in