What is the minimum flash rate for visible notification appliances?

• A. 2 flashes per second
• B. 1 flash per second
• C. 1 flash every 2 seconds
• D. 0.5 flashes per second

Answer: (B)

Visible notification appliances rely on a steady flash to grab attention quickly, including for people with hearing impairment. The standard sets the minimum at one flash per second, meaning the light must cycle on and off at a rate of 1 Hz. This rate is fast enough to be noticeable in various lighting conditions and distances without being overly distracting. A slower rate, such as every two seconds, might not be perceived promptly during an alarm. A faster rate, like two flashes per second, would still meet the requirement but is simply not the minimum. So, one flash per second is the correct minimum.