During Bhastrā: pump the breath vigorously through the nose — one forceful inhale plus one forceful exhale per second, like a bellows fanning a fire. Then take one full deep inhale, hold with full kumbhaka, and release slowly. Considered the most powerful of the classical prāṇāyāmas. Avoid if you have high blood pressure, heart conditions, epilepsy, or are pregnant. Do not practise on a full stomach.