Maintaining homeothermy (stable body temperature) requires equilibrium between heat generated by the organism and dissipated to the environment [1]. Each living cell of the body produces heat as a side-effect of metabolic processes. Apart from this “basic” production, heat is generated also during physical effort, and its amount is proportional to the intensity of the activity. It is worth noting that certain amount of thermic energy may be “absorbed” from the outside via the same pathways it is lost. On a sunny winter day, when ambient temperature is 0–5°C, we may do without warm clothing as we absorb significant amount of solar radiation. In a cold room we stand close to a hot radiator, and desiring to get warmer faster, we put our back close to it. In moments of danger we have one more heat generation method at our disposal – shivering (see: Chapter 1).

Intensity of metabolic processes, including heat generation, depends on many factors: weight, sex, age, physical activity, ambient temperature, type of cover/clothing. In emergency care, the disorders reducing metabolic rate may be of additional importance, in particular: severe injuries, exhaustion – understood as deficit of energy substrates, and influence of medications.

Mechanisms of heat loss (conduction, convection, radiation and evaporation) have been described in Chapters 1 and 3. As human being loses about 90% of heat through skin, the prevention of thermic imbalance should focus on body surface insulation. Are we able to stop the processes of heat transferral to the surroundings entirely? Unfortunately not. Yet we can minimise them to such an extent so as to compensate even a severely limited production. Of course, in extreme cases the balance may be “tipped” by heat delivery, but this chapter aims to concentrate on means to prevent heat loss, i.e. thermal insulation.

First of all, let us use an example to illustrate the pathways of heat loss and counteraction measure. Let us compare streams of heat leaving the organism in two places: vicinity of Supraśl (Poland) and area of Spitsbergen (Norway) [2, 3] – Table 1.