There are irritating gases in many industrial production processes, such as welding, electroplating, smelting, chemical industry, petroleum and other industries. Most of these gases are corrosive, and entering the human body through the respiratory tract will cause acute poisoning. The toxic effects of irritating gases on the body are manifested in different degrees of irritation to eyes, respiratory mucosa and skin. Generally, it is mainly local damage, but it can also cause systemic reactions. "Tri-acid" steam can not only stimulate respiratory mucosa, but also cause skin burns; Long-term exposure to low-concentration acid fog will also stimulate teeth and cause tooth erosion. Chlorine, ammonia, sulfur dioxide, sulfur trioxide, etc. It has high water solubility, and it is easy to cause injury when it meets wet parts. If inhaled, these gases will dissolve in the mucosa of the upper respiratory tract, directly stimulate the mucosa, cause congestion, edema and increased secretions of the upper respiratory tract mucosa, produce chemical inflammatory reactions, and have symptoms such as runny nose, itchy throat and coughing. Nitrogen oxides, phosgene, etc. The water solubility is small, and it rarely causes hydrolysis when passing through the upper respiratory mucosa, so the irritation of the mucosa is slight; However, it can penetrate into bronchi and alveoli continuously, and gradually react with the moisture on mucosa, which has a strong stimulation and corrosion effect on lung tissue, and even appears pulmonary edema in severe cases.
The prevention and control of irritating gases focuses on preventing accidents, running, escaping, dripping and leaking, and recycling and comprehensive utilization of waste gas. The automation, mechanization and assembly line of the production process adopt automatic control technology, which can automatically adjust and maintain the normal operation state and prevent accidents; Improve the air tightness of equipment and prevent corrosion and cracking of metal equipment; Select the appropriate ventilation mode according to the characteristics of the production process. Strengthen personal protection and wear corrosion-resistant protective articles, such as PVC, rubber products, rubber gloves, protective glasses and protective rubber shoes. When exposed to corrosive liquid poisons (such as acids and bases). Wear a gas mask or protective mask; Apply skin care cream. Strengthen health monitoring, do a good job in pre-job and regular physical examination, and find that patients with allergic asthma, allergic dermatosis or eczema, chronic respiratory diseases such as eyes, nose, throat and trachea, tuberculosis (including stable period) and heart disease should not be exposed to irritating gases.
(1) sulfur dioxide
Sulfur dioxide mainly comes from the combustion products of sulfur-containing fossil fuels (coal and oil), and there are also waste gases containing sulfur dioxide in the production processes of roasting metal minerals, bleaching wool and silk, chemical pulp and acid making. Sulfur dioxide is a colorless, strongly irritating gas, which smells like sulfuric acid and is easily soluble in water. When it comes into contact with water vapor, it produces acid, which has a strong stimulating and corrosive effect on eyes and respiratory tract, and can cause inflammation of throat and bronchus, respiratory paralysis and pulmonary edema in severe cases. It is an active poison, which can be oxidized into sulfur trioxide in air to form sulfuric acid smoke, and its toxicity is 10 times greater than that of sulfur dioxide. Sulfur dioxide has a strong corrosive effect on respiratory organs, causing inflammation of nose, throat and bronchus. When the concentration of SO2 in the air reaches 0.0005%, the olfactory organs can smell pungent odor. When it reaches 0.002%, it has strong stimulation, which can cause headache and sore throat; When it reaches 0.05%, it can cause bronchitis and pulmonary edema, and it can lead to death in a short time. The safety and hygiene standard of sulfur dioxide in China is 15mg/m3.
(2) Nitrogen oxides
Ammonia oxides mainly come from fuel combustion and chemical, electroplating and other production processes. NO2 is a reddish-brown gas, which strongly stimulates respiratory organs and can cause acute asthma. Experiments show that NO2 can rapidly destroy lung cells, which may be one of the causes of emphysema and lung tumors. When the concentration of NO2 is 1 ~ 3 ppm, odor can be smelled. When the concentration is 13ppm, there is acute irritation to eyes and nose; When the concentration is 16.9ppm, breathing 10min will reduce the vital capacity and increase the airflow resistance in the lung.
(3) phosgene
Occupational acute phosgene poisoning refers to a systemic disease with acute respiratory system damage caused by inhalation of phosgene in production environment. In the production of phosgene, phosgene is organically synthesized under the high temperature combustion of chlorinated hydrocarbons, which can be contacted in the production of dyes, pesticides, medicines and so on. When the concentration of phosgene in the production environment is 20~30mg/ m3, acute poisoning may occur, and contact with 100~300mg/ m3 for10 ~15min may cause serious poisoning or death.
Clinically, it mainly causes respiratory mucosa irritation symptoms, and in severe cases, it causes bronchospasm, chemical inflammation, pulmonary edema, asphyxia and so on. After acute poisoning is cured, there is generally no sequelae, and severe cases can leave obvious respiratory symptoms or signs.
2. Prevention of asphyxiating gas poisoning
Common asphyxiating gases include carbon monoxide, hydrogen sulfide and cyanide. After they enter the human body, they hinder the ability of blood to transport oxygen or the ability of tissues to use oxygen, leading to hypoxia in tissues and causing harm. The main preventive measures are to strengthen closed ventilation, strict safety operation procedures, strengthen publicity and education, popularize first aid and prevention knowledge, and do a good job in health monitoring and regular physical examination before taking up their posts.
(1) carbon monoxide
Carbon monoxide is a colorless and odorless gas, which can be evenly dispersed in the air and slightly soluble in water. Generally, it is inert in chemical properties, but it can cause explosion when the concentration is 13 ~ 75%. Most of carbon monoxide is the product of incomplete combustion of industrial furnaces, internal combustion engines and other equipment, and there is also leakage of gas equipment. Carbon monoxide is toxic, and its affinity with human hemoglobin is 250 ~ 300 times greater than that of oxygen and human hemoglobin. After human body inhales air containing carbon monoxide, carbon monoxide quickly combines with heme, which greatly reduces the ability of lycopene to absorb oxygen, causing hypoxia in various tissues and cells of human body, causing suffocation and blood poisoning, and even death in severe cases. When the concentration of CO in the air reaches 0.4%, people will lose consciousness in a short time, and if they are not rescued in time, they will be poisoned and die. The relationship between carbon monoxide poisoning degree, poisoning speed and carbon monoxide concentration is shown in the following figure.
Because carbon monoxide is colorless and odorless, it can be mixed with air evenly and is not easy to be found, so it must be guarded against. The safety and hygiene standard of carbon monoxide in China is 30mg/m3.
Relationship between the degree and speed of human poisoning and carbon monoxide concentration
(2) Hydrogen sulfide
Colorless flammable gas, with obvious rotten egg smell. Soluble in water, ethanol, gasoline, kerosene and crude oil, with spontaneous combustion point of 246℃[8] and explosion limit of 4.3%~46%. Hydrogen sulfide is burned in a blue flame to produce sulfur dioxide. When mixed with air, it will cause a strong explosion.
Hydrogen sulfide is produced by the reaction of iron sulfide dilute sulfuric acid or hydrochloric acid, or by the reaction of hydrogen and sulfur vapor. Hydrogen sulfide is rarely used in production, and is generally used as a by-product in chemical reactions, such as the mining and refining of sulfur-containing petroleum, viscose rayon, synthetic rubber, dyes, leather making, sugar making, etc. (it can be used as an analytical reagent and disinfectant in agriculture). Can also be released in the process of fermentation and corruption of sulfur-containing organic matter. The acute poisoning accidents listed in this paper are mostly the latter, and hydrogen sulfide is often encountered in mines, gas wells and sewers.
Hydrogen sulfide is a poison that strongly stimulates nerves and can cause suffocation. Even low concentration of hydrogen sulfide has obvious irritation to eyes and respiratory tract. At low concentration, the smell of rotten eggs can be detected, but continuous contact dulls the sense of smell, and high concentration of hydrogen sulfide can quickly numb the sense of smell. The national hygienic standard is 10mg/m3.
In mild poisoning, eyes appear photophobia, tears, stinging eyes, eyelid spasm and blurred vision; Nasopharyngeal burning sensation, cough, chest tightness, nausea, vomiting, dizziness and headache can last for several hours, fatigue and leg pain. In moderate poisoning, the consciousness is blurred, and you may lose consciousness for a few minutes, but you have no difficulty breathing. In severe poisoning, people unconsciously enter a deep coma, accompanied by dyspnea, shortness of breath, gray cyanosis until dyspnea is relieved, tachycardia and paroxysmal tonic spasm. Inhalation of a large amount of hydrogen sulfide immediately produces hypoxia, which can cause "electric shock" poisoning, cause lung injury and lead to suffocation and death.
In the production process, sealing, ventilation and detoxification should be strengthened. The production process should be sealed, and the ventilation equipment should exhaust safely where hydrogen sulfide may escape. Enterprises should be included in regular health supervision, and the concentration of H2S in the air of production environment should be monitored. When it is necessary to enter a local space containing H2S to operate equipment or treat sewers, local ventilation should be conducted in advance to purify the air, and the concentration of H2S should be measured. The concentration of H2S should be measured frequently at work, and the presence or absence of H2S can never be detected by smell.
Personal protection should be strengthened where H2S has been found. Workers should wear oxygen respirator or gas mask with gray coded canister when entering, and workers with strong sense of responsibility must be supervised outside. Workers should wear chemical protective glasses when cleaning sewers or sewage pools.
Smoking and open flames should be prohibited in places where hydrogen sulfide is stored or used, and electrical equipment should be explosion-proof. During transportation, gas cylinders should be fixed and labeled as "toxic compressed gas", and stored in a wind-proof, rain-proof and sun-proof sealed room. The treatment and discharge of waste gas containing hydrogen sulfide shall comply with the environmental protection law. In order to reduce the harm of hydrogen sulfide to human body, it is suggested to choose relevant detection instruments (such as hydrogen sulfide alarm) to remind people to take timely measures to minimize the harm and loss.