PPE

What are the effects of low temperature operation on human body

The effect of low temperature operation on human body is not only the degree of low ambient temperature, but also depends on the relationship between human body’s degree of cold protection and warmth preservation, physical activity intensity, diet and health status in low temperature environment, that is, the relationship between low temperature and its action on human body – cold action intensity. Sometimes, although the working environment temperature is low, but the equipment is warm enough, the body’s thermal metabolism keeps balance, the skin temperature and body temperature do not drop, and the human body does not feel cold; On the contrary, when the ambient temperature is relatively high, if the body can not keep the balance of heat metabolism, cold sensation will appear if the individual’s cold protective equipment is not enough to keep warm, and it can also lead to cold injury when it is serious

effect on the body

the effect of low temperature operation on the body depends on the intensity of cold action. The greater the intensity of cold action is, the more obvious the effect of low temperature is, which is mainly manifested in the following aspects:

effect on skin temperature. After cold, the temperature of exposed skin first decreases, and with the extension of time and the increase of intensity, the skin temperature gradually decreases, The skin began to flush, followed by cold, swelling, numbness, pain and other symptoms, and the skin feeling gradually weakened, severe frostbite can occur

at room temperature, the skin temperature of bare hands is generally between 29 ℃ and 30 ℃. When the skin temperature of hand drops to 15.5 ℃, the operation function of hand is affected; The tactile sensitivity decreased significantly when the temperature decreased from 10 ℃ to 12 ℃; When the temperature drops to 4 ℃ to 5 ℃, it can almost completely lose touch (perception). Generally, the skin temperature of bare hands is kept above 20 ℃, and the hand operation function is basically normal

in the cold environment, the average skin temperature of clothing covering parts (referred to as average skin temperature) also changes. The normal average skin temperature of human body (chest, back, upper limbs and thighs) is about 33 ℃ – 34 ℃. For example, the average skin temperature of clothing decreased due to insufficient heat preservation: when it dropped to 32 ℃, about 16% of people felt cold; When the temperature dropped to 31 ℃, about 26% of the people felt cold; When the temperature dropped to 29 ℃, the occurrence rate of cold sensation reached 77%; When the temperature dropped to 28 ℃, 100% of the people felt cold (about 50% of them felt very cold and shivered)

effect on body temperature in cold environment, the change of body temperature is not as sensitive as the change of skin temperature, because the body has strong regulation function and is not easy to have large fluctuations. 1t should be noted that once the temperature drops significantly, the adverse effects may be more serious than the skin temperature drop

in the cold environment, only when the body heat loss exceeds a certain limit (50kcal is about 210kj), the body temperature will drop, and the drop range is generally not more than 1 ℃, which has no obvious adverse effect on human health and work ability

when the body’s temperature drops to 36 ℃, the body’s metabolic reflex increases (heat production increases), which is a protective reaction of the human body; When the body temperature drops to 35 ℃, there will be obvious shivering, which is called hypothermia; When the temperature drops to 34 ℃, the blood pressure drops, and the consciousness is affected: when the temperature drops to 33 ℃, the respiratory rate and heart rate decrease, and the blood pressure drops, which is called “severe hypothermia”; When the temperature dropped to 32 ℃~ 31 ℃, the blood pressure could not be measured, the consciousness was not clear, the shivering disappeared, and the pupil dilated; When the temperature dropped to 30 ℃ – 29 ℃, the consciousness gradually disappeared, the muscles became stiff, the pulse and breath weakened and decreased; When the temperature drops to 28 ℃, ventricular fibrillation will appear, and life is in danger: when the temperature drops to 20 ℃, the heart stops

the extreme drop of body temperature does not exist in the daily production process, and it can only be seen in the severe cold environment (especially outdoor operation in winter)

the effect on the whole body, after the body is cold, the first is the contraction of capillaries, the decrease of skin blood flow, resulting in the decrease of the temperature difference between the skin temperature and the ambient temperature, which is conducive to reducing the body heat dissipation, which is a protective reaction. However, due to the peripheral vasoconstriction, it can also increase blood pressure and easily cause brain accidents in patients with hypertension, which is also one of the reasons for the high incidence of stroke in cold areas

working in the environment with large temperature difference between cold and hot (such as cold storage) can destroy the adaptive relationship between human body and normal seasonal changes. Therefore, employees are prone to fatigue, burnout, cold, numbness, acid, toothache, frequent urination and other symptoms (similar to the so-called symptoms of summer air conditioning disease). Cold is also one of the inducing factors of Raynaud’s syndrome and peripheral facial paralysis

cold allergy cold can cause allergic urticaria. According to some foreign investigation data, the incidence of cold allergy in workers working in meat processing factory cold storage (- 3 ℃) is 27%, and cold urticaria mostly occurs between 30 minutes and 4 hours after cold exposure. Cold allergic urticaria can be divided into congenital (hereditary) and acquired

congenital cold urticaria is characterized by no swelling on the skin surface, elevated body temperature, leukocytosis and joint pain; Acquired cold urticaria accounts for about 67% of the total number of cold urticaria. 1t usually occurs 12 minutes after exposure to cold. 1t may have chronic swelling, which is different from congenital cold urticaria. Generally, it has no systemic symptoms

preventive measures

enough cold proof clothing should be worn for cold storage operation (and outdoor operation in winter). The amount of clothing heat preservation can ensure that the average skin temperature of the covered parts of clothing is not less than 33 ℃, or refer to requirements for cold proof and heat preservation of labor protective clothing (GB / t13459-92), and keep clothing dry. For the weak links of keeping warm, such as hands, feet, heads and ears, we should strengthen keeping warm, reduce the area of bare skin as far as possible, and ensure that the skin temperature of these parts is not less than 20 ℃. 1n the low temperature environment, the wind speed can increase the intensity of cooling effect. For example, in the 7 ℃ environment, the wind speed of 2m / S ~ 3m / S is equivalent to the temperature drop of 3 ℃ ~ 4 ℃, which can reduce the clothing heat preservation by 11% ~ 12%. Therefore, the size of the cold suit is also very important, neither too tight binding nor too loose binding, too tight binding affects the peripheral blood circulation, can increase the chance of cold influence or cold damage; Too loose will affect the heat preservation of the fittings

in winter, it is necessary to prevent excessive fatigue and drinking in order to prevent accidents. Do not sleep in cold and humid environment without special protection< The diet should be rich in fat, protein and vitamin B1. Lack of protein in food can weaken the body's tolerance to cold after working in cold environment, warm water bath is helpful to quickly reduce and eliminate the influence of cold. The clothing drying room and hot water bath should be attached to the low temperature operation (cold storage) workshop when evaluating the effect of cold, we should not only take the ambient temperature as the only index, but also take comprehensive measures based on the cold action intensity, which is a strong guarantee for the health, safety and high efficiency of cold workers

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