Multiple purchases by a few hitting O2 concentrators retail supply Synopsis ET spoke to six top executives in leading companies and importers, who said they are fielding many requests from individuals who want to buy multiple units. These executives spoke off the record. Maximum multiple purchase requests are from New Delhi, these executives said. Other requests are from Mumbai, Bengaluru and a few other cities. Oxygen concentrator supplies are slowly increasing. But multiple purchases — up to five or six units per person — by politicians, senior bureaucrats, industrialists, top cops, high net worth individuals and other influential people are thinning out supplies to retailers and online sellers.