At the heart of the 2019 anti-government protests that swept Chile was the Plaza de la Dignidad, an occupied roundabout in central Santiago. The plaza became a locus for police violence, including the extensive use of chemical agents such as tear gas against peaceful protesters.

On 20 December 2019, hundreds of tear gas canisters were deployed against protesters in an egregious display of disregard for public health by Chilean authorities. Forensic Architecture and the Chilean medical-activist No+Lacrimógenas worked together to analyse the use of tear gas by police on that day, and the scale of the health risks posed by it.