The poor air quality accompanying rapid economic growth in China attracted public attention worldwide when severe haze episodes caused by PM2.5 broke out in several major Chinese cities in 2011 and again in 2013 and early 2014. Previous studies have focused on the source of haze and its health impacts. Our study is the first to provide an analysis of pollution avoidance behavior by the Chinese in response to the recent haze episodes. We track the spatial-temporal variation of daily sales of anti-PM2.5 facemasks. In a standard utility maximization framework, the demand for anti-PM2.5 facemasks is a function of their price, the price of substitutes and other demand shifters affecting risk perceptions (visibility, level of PM2.5, haze alerts). We investigate whether an averting behavior exists, and how the purchases of masks depend on PM2.5 levels, and other factors directly observable: visibility and alert information. By providing insights on how citizens respond to air pollution, our research can help inform government agencies on how to better formulate policies to reduce exposure to air pollution and to more effectively communicate pollution alerts to those affected.