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A laborer received major blunt force and lacerating injuries in the early morning of March 29, 1974, when he fell through a hole in the second floor of an unfinished room in a federal building under construction in Washington, D.C. This room faces Third Street North West, in a roughly westerly direction. I was asked to investigate the role, if any, that the illumination level in the room may have played in this accident.
The building and the room were in an early state of construction. The multi-story building had been completely framed, with the outer walls in place, and individual rooms were being finished. In the room from which the fall occurred, the floor, walls and ceiling on the dates of my inspection consisted only of concrete. Dark stone or gravel was embedded in the wall concrete. This concrete reflected very little incident light, and the doorways were as yet unframed. A single, dark-tinted window had already been installed, constituting the entire outer wall. The window appeared to have a filtering or light-blocking effect of 10 to 20 percent. Two bare 100-watt bulbs, hanging from the ceiling, had been temporarily installed to illuminate the room. The bulb located closer to the accident site was inoperative, but for the purpose of the post-accident investigation was assumed to have been functioning at the time of the accident. This bulb was located about 10 feet measured horizontally from the edge of the hole in the northeast corner of the room through which the laborer had fallen.
The hole measured about 5 feet by 2½ feet. It was not covered, and artificial light could be seen coming up from the floor below. A barricade consisting of 4-inch by 4-inch framing and 1-inch by 6-inch bracing had been erected around this hole after the accident. A heavy concentration of stacked lumber obscured a direct view of the hole in the floor. There was considerable debris and building materials strewn on the floor throughout the room, which measured about 39 feet by 45½ feet. It was unclear why the flooring in this corner of the room was not completely covered: it possibly was to serve as a utility service shaft.
Between 7:30 and 8 a.m. on April 29, 1974, I measured illumination levels in foot-candles at various locations in the room with an illumination meter. A foot-candle is defined as “a unit of direct illumination on a surface one foot from a uniform point source of one international candle.”
While I was taking illumination level measurements, the sky was clear and slightly cloudy. No direct sunlight entered the room because of the early hour, and because the window faced in a roughly westerly direction. A District of Columbia Standard, Section 11-21021, for minimum illumination level, effective August 1, 1968, was relied upon for this analysis. It required 10 foot-candles of illumination in the working area. The current U.S. Department of Labor OSHA Standard during construction, 29 CFR 1926.26, requires 5 foot-candles for “general construction area lighting.” The generally recognized illumination standard in various working situations is the IES Lighting Handbook, published by the Illuminating Engineering Society of North America. The most applicable “illuminance” category found in this handbook was “Building (construction) Outdoors,” which calls for 10 foot-candles.
A horizontal illumination level measurement made on the floor at the hole through which the laborer had fallen was 0.2 foot-candles. A vertical illumination reading, taken with the light meter’s diffuser (light collector) resting vertically against the wall adjacent to the hole in the floor, collecting both the light penetrating the window from outside, and the direct rays of the overhead bulb was 0.8 foot-candles. No correction was made for the differences in illumination levels received from the outside on the two different dates (March 22 versus April 29). An appropriate correction would slightly reduce the probable value of the illumination levels on the former, accident date. A witness stated that the sky was overcast on the morning of the accident date, and the laborer had been working in almost “pitch darkness.”
Referring to the illumination standards, the measured illumination levels were at best ½5 of the required OSHA level, and 1/50 of the required IES and District of Columbia levels.
Other factors contributing to the accident were the lack of a guard to prevent the fall, as called for in OSHA 29 CFR 1926 Subpart M, “Fall Protection,” and the generally unpoliced and cluttered nature of the floor on which construction work was in progress, which was prohibited by OSHA 29 CFR 1926.25, “Housekeeping,” particularly in paragraph (a). EC
MAZER is a consulting electrical engineer who currently specializes in electrical safety issues. His telephone number is 202.338.0669, and his e-mail address is [email protected].