Reza Ganjavi sits on a white leather sofa in the basement of his house, just outside of Zurich, Switzerland. In his hand, he holds a radiation detector. The device, which is roughly the same size as a mobile phone and costs around $250, is extremely important to him. 

Suddenly, the detector starts to emit a squealing sound. “Is your phone not on flight mode?” he asks. 

Before we can continue with the interview, I quickly adjust the settings on my cell phone.

In an increasingly networked world, Ganjavi is one of a growing number of people who consider themselves acutely sensitive to the technology used to provide wireless and cellular internet connections. The condition is sometimes called “electromagnetic hypersensitivity” or EHS.