An outdoor laser light show/demonstration is considered to be a laser product by the Food and Drug Administration’s Center for Devices and Radiological Health (CDRH) and, if the irradiance is greater than 5 miliwatts per square centimeter, the demonstration requires a variance to Title 21, Code of Federal Regulations, Section 1040.11c. The variance (issued by the CDRH) requires the laser user to notify the Federal Aviation Administration (FAA) of the proposed laser operation and resolve any objections that the FAA may have.
If a perfectly diffuse, perfectly reflecting surface has one foot-candle (one lumen per square foot) of illumination falling on it, its luminance is one foot-Lambert or 1/pi candles per square foot.