Figure 1. Ergonomic installation height for a wall-mounted work station.
Architects, ergonomists, and interior designers use standard anthropometric tables to determine the normal range of human physical variation. Fixture heights (i.e., the distance from the floor to the opening of the sharps disposal container) are commonly designed to accommodate 95% of the adult population. An ergonomically acceptable range for fixed installations (i.e., containers located in permanent, wall-mounted holding brackets) can be calculated to facilitate the reduction of sharps-related injuries and standardize the container height location within the health care facility. HCWs should be able to comfortably view the entire inlet opening of the disposal container, and containers should be located within arm's reach. Neck and eye fatigue is most effectively reduced when objects to be viewed are slightly below eye level (i.e., 0 to 15 degrees below eye level).
Installation heights vary, depending on whether the installation is designed to be a standing workstation or seated workstation. Maximum and minimum heights for both design situations can be calculated by establishing the eye-level height for each design (standing or sitting), the maximum thumb tip reach (MTTR)* of the target adult female population and the drop in inches based on an angle of 15 degrees. The basic formula is as follows:
fixture height = (eye-level height) – (tangent 15°)(MTTR)
However, in observations of workers using fixed, wallmounted containers, nearly all workers bent their elbows and wrists when approaching sharps disposal containers to dispose of used sharps and actually stood closer to the container rather than extending their arms to their maximum reach. On the basis of these data, the calculation can be enhanced to accommodate actual behavior. The upper and lower ranges for the installation height can be modified by allowing for the reach behavior of workers. Thus the middle 50% distance of the MTTR was used to adjust for human behavior and provide for a more functional installation height range.
If eye level equals 57 inches and the modified MTTR is used,
fixture height = 57 inches – (.2679)(18.7 inches)
and
fixture height = 57 inches – (.2679)(3.7 inches)
Therefore,
fixture height = 57 inches – 5 inches = 52 inches
and
fixture height = 57 inches – 1 inch = 56 inches
The optimal installation heights for fixed, wallmounted sharps disposal containers are
Seated workstation:§
38 to 42 inches above the floor on which the chair rests
Figure 1. Ergonomic installation height for a wall-mounted work station.
†All standard measurements were taken from tables contained in J. Panero and M. Zelnick's Human Dimension and Interior Space, 1979, pages 98 and 102.
‡Standing eye level includes a 1-inch shoe heel thickness and a 56.3-inch eye height.
§Seated eye level includes a 0.25-inch clothing thickness, 1-inch chair seat thickness, 14.9-inch popliteal height, and 27.4-inch erect sitting eye height.
