PEOPLE might once have considered oxygen a human right. But the pandemic has revealed that access to oxygen – in a pure form, for medical use – is a luxury in most low and middle-income countries. DAVID FAIREN-JIMENEZ, Reader in Molecular Engineering, University of Cambridge Getting access to pure oxygen for medical treatments is a complicated, expensive and often very dangerous business. The current situation in India is a harsh reminder of this issue. The second wave of COVID-19 has hit the country hard, the total number of deaths has just passed the 200,000 mark. Oxygen is in short supply.…