Hawan is the ritual act of praising almighty through oblations as submissions to god and seek hi blessings. The sacred act of Hawan is performed to eliminate effects of negative vibrations, Nazardosh or during occasions like Griha pravesh, start of new business or to seek blessings to achieve professional excellency or personal satisfaction. 
This purifying ritual helps dispel negative energies by creating a protective shield around the place where the ceremony is performed. The reciting of shlokas and mantras help humans come closer to almighty and seek blessing to enrich positive energies.