Television sets injure one child every 30 minutes in America, and the rate of emergency room visits is increasing with the popularity of flat-screen TVs, according to a new study.

Just over half (52 percent) of all TV injuries for those under 18 from 1990 to 2011 were due to the equipment falling and hitting the patient, said the study in the journal Pediatrics.

The number of falling TV injuries was 5,455 in 1990, but that more than doubled to 12,300 in 2011, the study said.

The next most common category was the patient striking a TV (38 percent), but those injuries dropped 68 percent over the 22-year study period.

Most injuries were not serious, and only 2.6 percent required hospital admission.

A total of 380,885 pediatric patients were treated in emergency rooms over the period studied, for an average of more than 17,000 per year.

Television sets are ubiquitous in American homes -- 99 percent of households own at least one television, and 55 percent have three or more, said the study.

The number of US households with multiple TVs has more than doubled since 1990, but researchers say this is not the sole reason for the increase in injuries.

"We speculate that changes in the location of TV placement in the home may be responsible," said the study.

There were three times as many injuries from a television falling from an armoire or dresser over the last two decades, it said.

"Older TVs may be relegated to less safe locations in the home, such as on dressers or other unsuitable furniture," said the study.

Meanwhile, the rising popularity of flat screen TVs, which are predisposed to tipping forward because they carry their weight toward the screen, may be another key factor, the researchers said.

"Lighter weights coupled with a less bulky design may make flat panels more easily tipped than CRTs (cathode ray tube) and may be contributing to the observed increase in the rate of injuries associated with falling TVs," said the study.

Previous research has found that 215 children died from a falling TV injury from 2000 to 2011.