The effects of protective clothing and its properties on energy consumption during different activities: literature review

There are many industrial situations where workers are required to wear personal protective clothing and equipment (PPC), for example, firefighters, chemical workers, cold store workers, army personnel and those working in the steel and forestry industries. Although this protective clothing may provide protection from the primary hazard, for example heat or chemicals, it can also create ergonomic problems. In recent years many PPC product standards have been introduced, these have helped to improve the quality of the protective clothing and so increased the safety of the workers. However, information on the effect of the clothing on the wearer and the interactions between PPC, wearer and environment are limited. Most PPC is designed for optimal protection against the hazard present, but this protection in itself can be a hazard. There are important side effects to protective clothing and typically with increasing protection requirements, the ergonomic problems increase. Often the main problem is the added load on the body in terms of weight. Also reduced mobility due to garment stiffness reduces the freedom of movement and may increase the risk of falls or getting caught in machinery. Even worse, the extra load and discomfort due to the protective clothing may tempt workers not to wear it when the primary hazard risk is low, leaving them unprotected if the hazard unexpectedly reappears or increases in strength. The problems of protective clothing can be seen as thermal, metabolic and performance issues. By creating a barrier between the wearer and the environment, clothing interferes with the process of thermoregulation, particularly reducing dry heat loss and sweat evaporation. The main metabolic effects come from the added weight of the clothing and the ‘hobbling effect’ due to garment bulk and stiffness, both of which increase metabolic cost so the worker has to expend more energy when carrying out tasks. Loss of freedom of movement and range of motion due to PPC can also lead to reduced performance. Current heat and cold stress standards consider the balance of heat production and loss but focus on environmental conditions and work rate metabolism. They also assume workers are wearing light, vapour permeable clothing. By failing to consider the metabolic effects of actual protective clothing, the standards underestimate heat production and therefore current standards cannot be accurately applied to workers wearing PPC. The effects of protective clothing on workers have been studied across a number of industries but studies have mainly concentrated on the thermal effects of clothing, such as heart rate, core temperature responses to different garments and on performance decrements caused by wearing PPC. Very few studies have considered the metabolic effects. Quantifying the effect of PPC on metabolic load based on the properties of the PPC was one of the objectives of the European Union THERMPROTECT project and the work undertaken for this thesis made up work package 4 of the EU project. The main objectives of the project were to provide data and models which allow the heat and cold stress assessment standards to be updated so that they need no longer exclude specialised protective clothing.