Except for tunnels, shafts, and other potentially dangerous places, which need 10 fc of light, OSHA advises that all have a minimum of 5 fc of illumination. The amount of light generated by a normal candle put one foot away from a surface is known as a one foot-candle. 5 fc of illumination, therefore, is the amount of light produced by five candles set one foot away from a surface.