Mosquite bite my foot

The next door's building is a massage salon where mosquito- expelling device roared loudly. Just before getting asleep at 11:30pm, I heard unfamilar sounds and jupmted up from bed. I saw cloudy smoke from my room's window. I promptly gathered my property and went down to the hotel reception to check whether the fire were going on. A security came in and heard the roaring sound and found it was not fire before seeing the smoke. As keeping my room's window open, some mosquitos entered and bit my foot while sleeping. Receptionist checked it was not bite by a malaria mosquito but a harmless mosquito. The hotel told me 'No notice from the salon before expelling. How did he find "Harmless one".