Influence of air cooling units on air quality--a pilot project

Air cooling units are said to pose a health risk to humans because of residual water and biological contamination. We measured particles 0.5 and 5 microm, ultrafine particles and bacterial counts near the outlet of 38 air cooling units and at the corresponding workplaces. Control measurements were performed in 17 rooms without air cooling units. There was no difference between bacterial counts measured near the outlet, at the typical workplaces and in control rooms. Measured bacterial counts near the outlet were between 15 and 950 cfu/m(3) (median 150), at the typical workplaces between 20 and 1685 cfu/m(3) (median 213) and in control rooms between 75 and 940 cfu/m(3) (median 240). Concentrations of particles and ultrafine particles were less in rooms with air cooling units than in control rooms. Thus, we could not find an impairment of air quality by air cooling units in our study. These results should be tested again in a greater study, primarily in another building than a hospital.