This study aimed to quantify the blood content of aerosols produced during dental, maxillofacial and autopsy procedures and to identify those activities which involve the greatest risk of infection due to exposure to blood-containing aerosols. A total of 132 air samples were taken in several dental cubicles, a maxillofacial operating theatre and an autopsy room. The concentration of haemoglobin (Hb) in the samples was quantified and, for each day of sampling, the concentration of blood/m(3) of air aspirated (muL blood/m(3) air) was calculated. Hb was detected in 38.64% of samples. The mean concentration of Hb in the samples was 0.10+/-0.19 microg Hb/m(3) of aspirated air, with a range of 0-0.72 microg Hb/m(3). No statistically significant differences in the concentration of blood aerosol per m(3) of aspirated air were noted among the three types of activity analysed (P>0.05). Although there is, as yet, no concrete proof of the risk of infection through blood-containing aerosols, minimising the production and dispersal of aerosols and spatters is strongly recommended.