1. The physiological effects
Human thermoregulation center at hypothalamus, under its control, produce heat and cooling in dynamic equilibrium, can maintain the normal body temperature. In movement in the environment of high temperature such as fire, the body's metabolism speeds up, heat production increases, the fireman body will use skin vasodilation, blood flow speed, increased sweat gland secretion, respiration, etc., will be in the heat generated by the multilayer structure to surface through the fire fighters clothing, by radiation, conduction, convection and evaporation heat, to keep the temperature within the normal range. According to research, the circulatory system at the same time, the peripheral tissue thermal conductivity value can increase 5-6 times, this is called the heat stress. Biology has this kind of stress ability, to ensure the survival under thermal environment. But there is a limit to people's ability to heat stress, but also has great individual differences. If firefighters extinguishing protective clothing breathable heat dissipation performance is bad, and in a hot environment movement time is too long, more than heat stress ability of the individual, will appear below the thalamus sweat central obstacles, the body does not through perspiration evaporation heat, make the accumulation of excessive heat in the body and lead to body temperature, sweat, firefighters shortness of breath, heart rate, pulse quickened. If not timely relief and recovery will make firefighters, dizziness, headache, flustered, nausea, vomiting, environment in hot summer, and may cause a fireman syncope or shock.
According to research, the influence of heat stress on firefighters also embodied in the accumulation of heat inside the firefighting clothing, a large number of sweat will cause the decrease of blood flow, especially the decrease of the amount of plasma. At the same time, increased body temperature cause vasodilation, blood vessel diameter increased, make more blood sedimentation in the venous system, the return of the heart blood is reduced, resulting in blood flow and blood pressure decrease quickly, the heart is unable to provide enough health at the same time meet the needs of muscle, myocardial and brain blood supply, easy to cause chest and heart attack. Firefighters is heart disease one of the leading causes of death, the United States each year from heart disease death firefighters more than accounted for about 40% of all deaths.
2. The psychological impact
Heat mass inside the fire protective clothing, can make the firefighters fatigue degree increase rapidly, power, a big drop in excitatory declined obviously, confusion, depression and other negative emotions rise, higher operating error count, right decline, mental decline, velocity, decreased sensitivity and so on, seriously affect the operational efficiency.