Merapi volcano had its largest eruption in 100 years in 2010, resulting in over 300 fatalities (from pyroclastic flows) and substantial, but short‐lived, ashfall over a 3‐week period. Yogyakarta city sits just 30km from the volcano. Face mask distribution was well documented during this eruption (Save the Children were involved and the Singapore Red Cross donated 1 million surgical masks).

The region was also subjected to 5cm of ashfall from Kelud volcano, 300km away, which erupted in Feburary 2014. We conducted an urgent pilot study to determine what sorts of masks the population were wearing, where they sourced them from and who was giving them advice to wear them, as well as whether people felt they were effective. The data from that study have informed the design of the social surveys that we will be conducting, and the masks collected will be used in the laboratory experiments.