Objectives: Dental procedures with high-speed instruments produce large amounts of aerosols. The present study aimed to clarify whether blood-contaminated aerosols were existent and floating in air during dental procedures and to evaluate the effect of an extraoral evacuator system. Method and Materials: An extraoral evacuator system with a test filter was used for sample collection at distances from 50 cm (n = 102) and 100 cm (n =124) behind the patient. A leucomalachite green presumptive test was performed on the test filter. One or more positive reactions on the test filter was considered a positive result, and the positive ratio in each procedure was compared. To assess the effect of the extraoral evacuator, an additional extraoral evacuator was introduced, and the positive ratio during third molar extractions at 100 cm behind the patient was compared (n = 55). Results: At 50 cm from the mouth of the patient during third molar surgery, full-crown preparation, inlay cavity (Black Class II) preparation, and scaling with an ultrasonic scaler, positive results were obtained in 92% (12/13), 70% (21/30), 35% (9/26), and 33% (11/33) of cases, respectively. At a distance of 100 cm, positive ratios sustained 90% (35/39), 48% (15/31), 29% (6/21), and 12% (4/33), respectively. When the second extraoral evacuator was utilized, the positive ratio, at a distance of 100 cm, decreased significantly from 90% (35/39) to 60% (33/55) (P = .0015, chi-square test). Conclusion: This study showed that blood-contaminated aerosols can be suspended in air, even in general dental settings, and that extraoral evacuators are useful for reducing contaminated aerosols. Keywords: aerosol, blood, infection control, leucomalachite green, occupational infection, splatter