The challenge of gutter oil is so rampant that the nationwide security equipment began a campaign in 2011 to stamp out the "4 black pests" (打四黑除四害) — black workshops, black factories, black markets and black gambling dens. There was some drilling to insert cables but any dust was cleaned up. https://thetopvideotube.blogspot.fi/search/label/url-HHsGyDomCQKwyFArt3CDokfJX