Muscle strain associated with operating three models of fire nozzles and subjective assessment of their ergonomic quality

Abstract

Firefighters are subject to high physical and psychological stress and fire fighting often requires mastering complicated tasks under adverse conditions. In this job, the handling of the hose/nozzle combination is a central and often performed task. The objective of this field study was to ergonomically evaluate different designs of 3 fire nozzles – a multi-purpose nozzle according to a German standard, a pistol nozzle (AWG), and a supposedly ergonomic nozzle (Quadrafog) – with respect to the muscle strain associated with performing standardized working tests. Eleven firefighters (10 males and 1 female, aged 27–54) used the 3 nozzles in the practice area of a fire station. For 3 different working tasks (straight stream, wide fog, and alternating operation), electromyographic activity was monitored continuously from 7 muscles of the right and left hand-arm-shoulder system using a PC-based mobile data registration system. Specially developed questionnaires provided subjective assessments of the ergonomic quality of the fire nozzles. The standard nozzle – which is still very frequently used – 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 high strain by the hose forces, which depend on water pressure and flow. AWG and Quadrafog led to substantially lower overall strain and smaller static components. Only in pure straight stream fire fighting was there no difference between the standard nozzle and the other models. High static portions characterize straight stream as well as wide fog operation. Both operations required small movements of the body so that the static portions became more noticeable. Overall, the AWG fire nozzle exhibited the most balanced strain profile with non-critical static values and a tolerable overall strain for alternating operations. These results are in accordance with the fire fighters’ subjective preference for this model.

It is unfortunate that currently the sole focus remains still on the price rather than the usability, which determines the physiological costs that must be paid by the operator. In the future, more attention should be paid to the compatibility between the characteristics of the human organism and the technical components of the tool.