Epilepsy and Strobe Lights
"What frequency of flashing light is most likely to trigger a seizure? This varies from person to person. Generally, it is between 5 and 30 flashes per second (hertz). While some people are sensitive at higher frequencies, it is uncommon to have photosensitivity below 5 hertz."
"Strobe lighting can trigger seizures in photosensitive epilepsy, thus most strobe lights on sale to the public are factory-limited to about 10-12 flashes per second in their internal oscillators, although externally triggered strobe lights will often flash as frequently as possible. At a frequency of 10 Hz, 65% of affected people are still at risk. The British Health and Safety Executive recommend that a net flash rate for a bank of strobe lights does not exceed 5 flashes per second, at which only 5% of photosensitive epileptics are at risk. It also recommends that no strobing effect continue for more than 30 seconds due to the potential for discomfort and disorientation."
"Under the Americans with Disabilities Act, most workplaces and places serving the public, including theaters, restaurants, and recreation areas, are required to have fire alarms, which flash as well as ring so that people who cannot hear or cannot hear well will know that there is an emergency.
To reduce the likelihood of the strobe light triggering a seizure, the Epilepsy Foundation?s professional advisory board recommends that the flash rate be kept to under 2 Hertz with breaks every so often between flashes; and flashing lights should be placed at a distance from each other and set to flash together at the same time to avoid an increase in the number of individual flashes."
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