Out of home advertising is a growing $6.8 billion industry, and digital billboards are expected to be the fastest area of growth within the medium. Billboard companies such as Clear Channel Outdoor and CBS Outdoor are quickly launching digital networks or replacing old billboards with digital, but some controversy surrounds the new technology. While the Outdoor Advertising Association of America calls the display on a digital billboard “similar to static billboards,” and mandates that an image not change more often than every six to eight seconds, some reports in the media describe the billboards as “plasma TVs” and wonder whether they pose safety hazards.