INFECTION PREVENTION
Air and surface contamination – proving a measurable relationship
Andrew Kemp and Denise Hanson describe a long-term project to measure air and surface contamination in a variety of settings across a university campus. The study set out to evaluate cleaning technologies and the relationship between air and surface contamination levels.
The British Institute of Cleaning Science (BISc) in association with the Cleaning and Support Services Association (CSSA) and Surrey University undertook a 12-month study to determine if there is a quantifiable relationship between air and surface contamination levels in the University classrooms, bathrooms and sports facilities. The study used student classrooms and sports facilities at the University of Surrey, UK. This study was peer reviewed and published in the American Journal of Biomedical Science and Research in January 2026.1 In total, 740 bacterial cultures using blood agar plates, 740 live bacteria specific rapid metabolic assays (BSRMA)2 measuring colony forming units (CFUs), and 8,400 air particle count samples (APCs) of between 0.5 and 1 microns, were taken from 10 busy rooms (including classrooms) at the University of Surrey. One room was used as a control, with no changes made from the routine cleaning regimes, disinfectants and cleaning materials. The rooms treated were blinded to the cleaning operatives. Prior to any changes, rooms were tested to give base readings after routine standard cleaning, and before the start of the working day. Rooms were tested again after four to six weeks, and after 10 weeks, over an academic year. The 10-room study included a sub-sectional study using three rooms with the addition of new disinfecting technologies for both the air and surfaces, to see if the test results altered when these technologies were used.
In addition, due to the work underway
by the United Nations and the World Health Organization to set indoor air quality standards using CO2
determining risk factor,3 levels as a the relationship
between air and surface decontamination techniques and CO2
levels, were tested by
Professor Prashant Kumar’s team from the Global Centre for Indoor Air Quality Testing, also based at the University. The results showed that a direct
correlation of approximately 10:1 surface CFU counts to air particle counts of between 0.5 and 1 micron, can be drawn
between the air counts taken 20cm above the surface, and an assumed approximate surface count of live bacteria. The study also showed that significant improvements in both air and surface counts could be gained, due to the introduction of new cleaning technologies.
However, these did not affect the CO2 levels.
Background There are numerous papers showing the significance of surfaces in the potential for cross infection.4,5
With
The study used student classrooms and sports facilities at the University of Surrey, UK. April 2026
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