To examine the effect of a newly-developed tracheal detecting-bulb (TDB) in preventing the spray of contaminants in patients' exhalent during emergency endotracheal intubation procedure. 62 emergency patients (male or female, age 21-73 years, weight 47-83 kg, with different levels of consciousness and spontaneous breathing) were randomly divided into two groups (n =31 each) to receive endotracheal intubation by an anesthesiologist with more than 17 years of experience, with (TDB group) or without (control group) a TDB connected to the tracheal tubing. Records were taken regarding the patient's coughing, expansion / contraction of the TDB, the operator's feeling of the patient's exhalent on his face / neck and the contamination of these areas by blood / secretions from the patients in the due course. In TDB group, expansion / contraction of TDB occurred in all cases, but the operator felt no exhalent in any of them. In 9 cases the patients coughed but the operator was contaminated only in 2 cases. While in control group, the patients' exhalent was felt in 16 cases. Coughing were recorded in 7 cases, and the operator was contaminated in 11 cases. In comparison with the control group, TDB group had significantly lower(both P < 0.05), incidence in feeling the exhalent (0 vs. 16), and contamination by blood or secretions (2 vs. 11) although the two groups had no significant difference in the incidence of coughing (9 vs. 7, P > 0.05). TDB can play an important role in blocking the spray of contaminants in patients' exhalent during endotracheal intubation.