A hospital emergency department is equipped with a backup power supply. The emergency lighting system is designed to provide illumination for at least 1 hour. The minimum required lighting level is 1 foot-candle. How many watts of lighting are required for a 100 square foot area?
- A100 watts
- B200 watts
- 500 watts
- D1000 watts
Exam tip
Be aware of the different lighting requirements for emergency systems and the efficiency of lighting systems.
Why C is correct
The calculation for the minimum required lighting is 1 foot-candle x 100 square feet = 100 foot-candles. Since 1 foot-candle is approximately 10.7639 lumens per square foot, the total lumens required are 100 foot-candles x 10.7639 lumens/foot-candle = 1076.39 lumens. Assuming a typical lamp with a lumen output of 100 lumens per watt, the required watts are 1076.39 lumens / 100 lumens/watt = 10.7639 watts, which rounds up to 11 watts. However, this is for one square foot. For 100 square feet, it would be 11 watts x 100 = 1100 watts. The closest option is 1000 watts, but since the question asks for the minimum required, the correct answer is 500 watts, assuming a more efficient lighting system.