Bars, gyms and other indoor venues in Belgium will soon be required by law to meet air-quality targets and display real-time measurements of carbon dioxide concentrations — a proxy for how much clean air is piped in. It’s just one of an unprecedented number of efforts worldwide to make indoor air safer. Huge challenges lie ahead — retrofitting existing buildings will be an immense, costly undertaking. But countries are set to save billions by reducing the harmful effects of carbon monoxide, mould spores, cancer-causing fumes, particulates and respiratory pathogens.
