The limited space is in a closed or semi- closed , and the entrances and exits are limited, and the natural ventilation is poor, which may easily cause the accumulation of toxic, harmful, flammable and explosive substances or insufficient oxygen content. In addition, the working environment is greatly affected by natural weather, and adverse weather such as high temperature and high humidity exacerbates the deterioration of the space . Hazardous factors in confined spaces are mainly poisoning, asphyxiation due to lack of oxygen, explosion and other harmful factors.
poisoning hazard
There are a lot of toxic substances , and once people touch it, it is easy to cause chemical poisoning, which may lead to death. Common toxic substances include hydrogen sulfide, carbon monoxide, benzene series, volatile organic solvents, etc.
Hydrogen sulfide is a colorless asphyxiating gas with the smell of rotten eggs and a strong nerve poison. Heavier than air, it is easy to deposit at the bottom of pits, pools and wells, and may cause "electric shock-like" death. Operators are very likely to be exposed to hydrogen sulfide when cleaning and dredging biogas digesters, sewers, garbage stations, septic tanks, and sewage wells .
Carbon dioxide is a colorless, odorless, non- irritating gas that is explosive. Generally, mild carbon monoxide poisoning will cause severe headache, dizziness , nausea, vomiting, malaise, lack of energy, etc.; severe carbon monoxide poisoning can lead to deep coma, and severe cases can lead to death. For example, the accumulation of carbon monoxide caused by electric welding operations, the leakage of residual carbon monoxide etc.
An organic solvent is a liquid composed that dissolves another substance. Organic solvents at normal temperature and pressure are in liquid state and are volatile. The main route of poisoning is inhalation , and it can also be poisoned through skin contact or absorption through the digestive tract. For example, when painting , cleaning and repairing the reactor (tower), poisoning will be caused by contact with volatilized organic solvents such as benzene, toluene, and xylene .
Hypoxic asphyxia
Due to poor ventilation, biological , the limited space will form a hypoxic state. Once the oxygen concentration in the air is lower than 19.5%, there will be a risk of hypoxia, which may lead to hypoxia and suffocation. Accidents happen. Common causes of oxygen deficiency are carbon dioxide and inert gases. Carbon dioxide is heavier than air . In various mines, cellars, cabins, cold storages and other places with poor ventilation for a long time, it is easy to occupy space, resulting in low oxygen concentration and hypoxia. In addition, inert gases such as nitrogen, argon, helium, and water vapor can also cause oxygen deficiency. Inert gas is commonly used in industry to flush reactors, storage tanks, steel cylinders and other containers. If there is too much inert gas remaining in the container , simple hypoxia or suffocation will easily occur when the operator enters. Methane and propane can also cause hypoxia or suffocation.
explode
There may be a large amount of flammable and explosive . When the concentration is higher than the lower limit of explosion, it will explode or burn when it encounters fire or provides certain energy in other forms . The high temperature generated by the skindeflagration , and the toxic substances produced can cause poisoning. The explosion limits of common flammable and explosive substances, such as the lower explosion limit of methane is 5%, and the upper limit is 15%; the lower explosion limit of hydrogen the upper limit is 45.5%; was 74.2%.
In addition to the above factors, there may also be life-threatening or health-threatening environmental conditions such as falling, drowning, object strikes, electric shocks, etc., which may cause safety accidents in confined spaces.
