Hazard characteristics of confined space operations

The operating environment is complicated

Limited space, poor ventilation, not conducive to gas diffusion

1. Produce, store, use hazardous chemicals or produce toxic and harmful gases due to biochemical reactions (protein spoilage), respiration, etc., and easily accumulate. After a period of time, it will form a relatively high concentration of toxic and harmful gases.

Observe ventilation at any time when working in confined spaces

2. Some toxic and harmful gases are odorless, which can make operators relax their vigilance and cause poisoning and suffocation accidents. In addition, the infiltration or sudden influx of undercurrents around some restricted operation spaces, collapse of buildings, or other liquid solids (such as mud The flow of sand, etc., and the use of electrical leakage in the operation and the machinery used in the operation pose potential hazards to confined space operators.

3. Some poisonous gases have a paralytic effect on nerves (such as hydrogen sulfide) when they are high in concentration, but they cannot be smelled.

Limited space lighting, poor communication, and difficulties in normal operation and emergency rescue

In addition, the infiltration or sudden influx of undercurrents around certain restricted working spaces, the collapse of buildings, or the flow of other fluid solids (eg, silt, etc. Workers pose potential hazards.

High risk, often causing serious consequences in the event of an accident

The poisoning and suffocation of workers occur instantaneously. Some toxic gas poisonings can cause death in minutes or even seconds.

Hydrogen sulphide (H2S) is a colorless gas with a special odor (odor egg flavor) that is easily soluble in water; its specific gravity is greater than air and can easily accumulate in poorly ventilated urban sewers, manholes, septic tanks, lagoons, Pulp ponds and other types of fermentation ponds and vegetable marinating ponds and other low-lying areas (nitrogen-containing compounds such as proteins produced by decomposition). Hydrogen sulfide is a suffocating gas and is a strong neurotoxicant. H2S concentration of 0.4mg/m3, people can clearly smell the odor of hydrogen sulfide; 70 ~ 150mg/m3, inhalation of a few minutes that occurs olfactory fatigue and smell odor, the higher the concentration of olfactory fatigue Faster, the more likely it is to deter people from alertness. When it exceeds 760 mg/m3, pulmonary edema, bronchitis, and pneumonia can occur within a short period of time, which may result in life-threatening injuries. If it exceeds 1000 mg/m3, it can cause electrocution-like death.

Carbon monoxide (CO) is a colorless and odorless gas. It is slightly soluble in water and soluble in most organic solvents such as ethanol and benzene. It is a combustible and explosive toxic gas that can form an explosive mixture when mixed with air. It can cause burning explosions when exposed to open flames and high heat. . Carbon monoxide easily binds to hemoglobin in the blood (relative to oxygen) and causes tissue hypoxia. Mild poisoning patients have headache, dizziness, tinnitus, palpitations, nausea, vomiting, weakness, blood carboxyhemoglobin concentration can be higher than 10%; moderate poisoning in addition to the above symptoms, as well as skin and mucous membranes are cherry red, fast pulse, Irritability, gait instability, mild to moderate coma, blood carboxyhemoglobin concentration higher than 30%; severe patients deep coma, narrowed pupils, increased muscle tone, frequent convulsions, incontinence, shock, pulmonary edema, severe myocardium Damage and so on.

Suffocation: The process of causing an anoxic state in human tissue is called asphyxiation. The effects of different concentrations of oxygen on the human body are as follows:

It is easy to expand casualties due to blind rescue

A well-known multinational chemical company has done statistics. 50% of the deaths in restricted space operations were rescue workers, and the casualties were expanded due to improper rescue.

Due to the poor safety awareness and lack of safety knowledge, some restricted space operators and operators have not developed a restricted space safety operation system or an imperfect system, are not strictly enforced, and safety measures and guardianship measures are not in place or implemented. No hazard identification was done before operation, no targeted emergency response plan was formulated, necessary safety facilities and emergency rescue equipment and equipment were lacked, or although emergency response plans were prepared but training and drills were not conducted, operations and guardians lacked basic Emergency common sense and self-rescue and mutual rescue capabilities have led to the failure to implement scientific and effective rescue in the event of an accident, which has further increased casualties.

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