Presents the results of a survey of outdoor air pollutants measured at high and low levels in a variety of buildings to determine the preference for air intake locations for buildings. 

The low level measurements were undertaken at or near street level and the high level measurements tended to be at roof level, typically some 20 m above street level. The broad conclusion is that that there was a reduction in CO concentration (-13%) at high level, along with a reduction in oxides of nitrogen concentrations (-31%). The ozone concentration increased at high level (+56%), and, surprisingly, there appeared to be very little statistical difference in the airborne particles at high or low level.
 
Discusses these findings and identifies the benefits of introducing air intakes at high level to reduce the load from combustion products such as CO and oxides of nitrogen.