A NIOSH research team measured the concentrations of mercury (7439976) in personal and area air samples of an Ohio dental facility whose personnel used a household vacuum cleaner for cleaning carpets in operatories and other areas. No health hazard was found for the dental facility personnel except when the vacuum cleaner was used. Mercury concentrations immediately above the carpet in amalgam mixing areas measured shortly after vacuuming were often two to four times greater than those before vacuuming. Air samples taken near the operating vacuum cleaner suggested that the operator inhaled higher than recommended mercury concentrations. With the vacuum cleaner not in use, mercury concentrations averaging 7.5, 7.4, and 8.5 micrograms per cubic meter (microg/m3) were found for 6 to 8 hour personal samples, 6 to 8 hour area samples, and instantaneous personal samples, respectively. With the vacuum cleaner in use, mercury concentrations averaging 32 and 69microg/m3 were observed for 26 minute and instantaneous personal samples, respectively. The authors recommend that personnel only use vacuum cleaners specifically designed to handle mercury contamination where mercury use areas are carpeted. The best alternative is the elimination of carpets in mercury use areas.