Professor Cath Noakes studies how air moves and the infection risk associated with different ventilation systems. Early in the pandemic, she was invited to join the government’s Scientific Advisory Group for Emergencies, SAGE and asked to study the transmission routes for Covid-19. In July, together with many other scientists, she urged governments around the world and the World Health Organisation to recognise that Covid-19 could be transmitted in tiny particles in the air, even if the risk of getting infected in this way was much smaller than the risk from larger particles that travel less far. Her research highlights the importance of good ventilation as a way to stop the spread of infection in indoor environments. Being in a well ventilated space can reduce the risk of inhaling tiny airborne pathogens by 70%. Cath talks to Jim Al-Khalili about her journey from studying industrial processes to infection risk, her work on the airborne transmission of diseases and the challenge of designing buildings that are both well ventilated and energy efficient. Producer: Anna BuckleyPhoto credit: University of Leeds