Evaluation of the Ergonomic Quality of Fire Nozzles Via Electromyographic and Subjective Methods

Abstract

Firefighters are subject to high physical and psychological stress and fire fighting often requires mastering complicated tasks under adverse conditions while close to their stress limit. The handling of the hose/nozzle combination is a central and an often performed task. Therefore, it was the objective of a field study to ergonomically evaluate the various designs of 3 fire nozzles - multi-purpose nozzle according to DIN 14365-2, pistol nozzle AWG, and selectable gallonage nozzle Quadrafog - with respect to the muscular strain resulting from them. Objective characteristic data was obtained from strain values of 7 muscles of the right and left hand-arm-shoulder system of 11 firefighters via surface electromyography for 3 different working tasks (straight stream, wide fog, alternating operations). Specially developed questionnaires provided subjective evaluations of the tasks which were carried out by the subjects (Ss) with the fire nozzles and of the nozzles' ergonomic quality. The German standard nozzle is only suited for “water go” for extended periods of time, but not for dynamic work. Especially the nozzle operator's arm musculature is subjected to strain by the hose forces which depend on water pressure and flow. AWG and Quadrafog lead to substantially lower overall strain and smaller static portions. Only in pure straight stream fire fighting is there no difference between the standard nozzle and the other models. High static portions characterize straight stream operation as well as wide fog operation. Both operations require little movement of the body so that the static portions become more noticeable. However, the endurance level should not be exceeded as it was in this study. Overall, the AWG fire nozzle exhibits the most balanced strain profile with uncritical static values (up to 8%) and an overall strain of up to 30% for alternating operations. These results are in accordance with the fire fighters' subjective preference for this fire nozzle model.