Every year, millions of workers are injured on the job, and several thousand die as a result of those injuries. In 1970, Congress passed the Occupational Safety and Health Act (OSHA). Using standards set by OSHA, the U.S. Bureau of Labor works to reduce work-related injuries by setting safety guidelines and standards that employers must adhere to. One standard pertains to lighting or illumination. Depending on the industry, exterior lighting or illumination standards vary.
General OSHA lighting or illumination requirements for exterior worksites
Illumination in active work areas, such as cargo areas, needs to be an average minimum light intensity of five foot-candles. In other work settings, such as farms, OSHA requirements are that illumination be an average minimum light intensity of one foot-candle. The exception is when an organization keeps the lights dimmed for security purposes, but even then it must be a minimum light intensity of 1/2 foot-candle. When occasional work-related tasks require more light, OSHA requires supplemental exterior lighting—and it cannot be placed so that it shines in the eyes of employees.
Specific exterior lighting requirements for construction sites
In general, exterior construction sites must be illuminated to an average minimum light intensity of five foot-candles. However, in areas of excavation, concrete placement, access areas, storage, loading docks, refueling and maintenance areas, the requirement is three foot-candles.
Tunnels, shafts and general underground work areas
All tunnels, shafts and general underground work areas require an average minimum light intensity of five foot-candles. However, during drilling, scaling or mucking in these areas, an average minimum light intensity of 10 foot-candles is required.
measure illumination or foot-candles
The exterior lighting or illumination level in any work area or worksite is best measured with a light meter. This meter should read lumens per square foot, which is equivalent to foot-candles. You can get a light meter at any store that sells photography supplies.
A rough conversation of foot-candles to watts
To make a very rough conversation, a 100-watt incandescent bulb produces about 1750 lumens, or 137 foot-candles. So to light or illuminate an area that measures 5 by 5 feet to a light intensity of five foot-candles, you would need one 100-watt bulb.