It's a gas

摘要

One of the hidden glories of Victorian engineering is proper drains. Isolating a city's effluent and shipping it away in underground sewers has probably saved more lives than any medical procedure except vaccination. But out of sight is out of mind. And that, together with the inherent yuckiness of the subject, means that many old sewers have been neglected and are in dire need of repair. If that repair does not come in time, the result is noxious and potentially hazardous. All this neglect, though, makes it hard to know where best to apply the sticking-plasters. So Mark Hernandez of the University of Colorado, Boulder, and his team have been looking for an easily measurable signal that something is about to go wrong.