If you feel strongly that there is some negetivity in a place then remeber lord Ganesha and chant the below mentioned mantra by remembering your GURU/Guiding Spirit.
Manatra:
Om, Om, Om, Om, Om, Om, Om,
Aap sarpantu te bhuta ye bhuta bhuvi samstitha :!
Ye bhuta vigna karta raste gachantu shivajnaya !!
Iti Shivam samprarthya ! Om namo astraya fat !!
Iti talatrayam kritva bhutanuchatayet !!
After chanting above mantra make three big sounds of bells. Even clapping three time also will help.
Om.