Ergonomic Analysis of Extension Ladders

Abstract

Although the most serious accident mode associated with extension ladder use has always been “falling off the ladder” there has been increasing attention, recently, on “contact with electric current” or electrocution accidents primarily with aluminum ladders. The U.S. Consumer Product Safety Commission (CPSC) has made several recommendations to address this problem from a technical approach. They have proposed insulating and/or isolating the ladder electrically or replacing it with a fiberglass ladder. Long extension ladders are heavy, and proposed recommendations by the CPSC to make aluminum extension ladders nonconductive include replacing them with fiberglass extension ladders, which will definitely result in a heavier ladder. A heavier ladder has implications for the characteristics of the user population and for types of injury patterns.

Occupational accident data show that ladder associated accidents directly related to ladder weight, such as overexertion, are more likely. If ladder weight were increased for example, by using exclusively nonconductive fiberglass ladders, overexertion would be a greater concern. A statics model was developed that uses a variety of variables relevant to the ladder erection process to determine the amount of force required of users to erect various types of extension ladders. Anthropometric data on the male and the female adult population were compared to the ladder user requirements. The percentages of males and of females capable of erecting 12.2-meter (40-foot) extension ladders were determined. Only three percent of female adults have the strength and reach height to erect 12.2-meter (40-foot) fiberglass extension ladders. Mandated use of 12.2-meter (40-foot) fiberglass extension ladders would greatly restrict the numbers of females who could perform jobs requiring the use of such ladders.