Because the limited space is relatively closed, it is difficult for toxic and harmful gases to diffuse. If they accumulate to a certain extent, they can cause people to be poisoned. Faced with this "invisible killer", Xiaohan will take you to an in-depth interpretation.

Q1 What is a limited space?

Limited space refers to a space that is closed or partially enclosed, with restricted access but people can enter, is not designed as a fixed workplace, and has poor natural ventilation, which is likely to cause the accumulation of toxic and harmful, flammable and explosive substances, or insufficient oxygen content.

Q2 Where does the danger of limited space come from?

There is a deadly killer hydrogen sulfide in many limited spaces. When the concentration of hydrogen sulfide is low, it smells like rotten eggs. After inhaling it, it will affect the eyes, respiratory system and central nervous system.

Q3 What are the dangers of hydrogen sulfide?

When the concentration of hydrogen sulfide is high, it will paralyze the olfactory nerves, but there is no smell. Inhalation of a small amount of high concentration of hydrogen sulfide can be fatal in a short time. At the same time, hydrogen sulfide is flammable and can form an explosive gas mixture when mixed with air. It will cause combustion and explosion when exposed to ignition sources such as open flames and high heat.

Q4 What should I pay attention to when rescuing?

In recent years, the problem of blind rescue in limited space operation accidents is very prominent. If an emergency occurs, blind rescue must be eliminated to avoid the expansion of casualties.

In the past decade, Beijing's limited space poisoning and suffocation accidents have always accounted for a relatively high proportion of the total number of deaths in industrial, mining and commerce, especially the number of accidents and casualties in 2017. Although the relevant figures have decreased in the past three years, considering that limited space operations involve a wide range of fields, especially since there are more construction projects in Beijing this year, the number of related operations may increase compared with previous years, leading to a further increase in the risk of accidents. The Beijing Emergency Management Bureau analyzed the 26 incidents that occurred in Beijing in the past ten years (2011-2020) from six aspects: the time when the accident occurred, the location of the accident, the area where the accident occurred, the type of operation, the cause of the accident, and the direct cause of death. Poisoning and suffocation accident in limited space.

1 month of incident

Of the 26 accidents, 6 accidents occurred in July, 5 accidents occurred in August and September, 4 accidents occurred in June, 2 accidents occurred in April, and 1 accident occurred in January, February, March, and October. It can be seen that the accidents are mainly concentrated in the summer. The main reasons are as follows:

First, the summer temperature is high, which provides conditions for the generation and volatilization of toxic and harmful gases, and the limited space is narrow and blocked, which is not conducive to gas diffusion;

Second, there is a significant increase in summer rain, which leads to the formation of water in the limited underground space, which is conducive to the growth of microorganisms and generates toxic gases. Especially in the flood season, heavy rainfall washes the ground, causing drainage and sewage pipelines to be blocked by debris, and pipeline cleaning operations are significantly increased;

Third, the summer is relatively hot, and workers are subjectively unwilling to wear respiratory equipment and other personal protective equipment.

2 Location of the incident

There were 5 incidents in Chaoyang and Haidian Districts, 3 in Changping, Fangshan, Shunyi, and Tongzhou Districts, 2 in Daxing District, and 1 in Fengtai and Xicheng District. The limited space accidents are mainly concentrated in densely populated urban areas, which is related to the denser distribution of municipal underground pipelines and the larger amount of limited space operations.

3 Incident space

Of the 26 accidents, 22 occurred in the underground limited space area, 3 occurred inside the equipment, and 1 occurred in the limited space area above ground. A total of 12 sewage wells (pools) occurred in the limited underground space, including 3 electric wells, 2 thermal wells, 1 gas well, 1 communication well, 1 in pipeline, and 2 other wells. Confined space accidents that occurred in sewage wells (pools) accounted for the highest proportion, accounting for about half of the total number of accidents. In addition to sewage wells (pools), 4 of the 10 underground limited space accidents were clearly related to sewage. The main reason was Because there are more hydrogen sulfide, phosphine and other volatile toxic substances in sewage, the operation risk is significantly higher than other limited space areas.

4 Types of incidents

Among the 26 accidents, 11 accidents occurred during clean-up operations, 9 various construction operations, 4 survey operations, and 2 maintenance operations. Clean-up operations are relatively large due to the presence of more toxic substances in the environment; in addition to the original environmental risks of limited space, construction operations may also cause accidents due to the precipitation of construction materials or the leakage of materials in the construction pipelines. The safety risks of the four cases are relatively simple. The operators may relax their safety vigilance because there is no water and toxic gas in the tube wells, which may lead to accidents.

5 The cause of the accident

The direct causes of the 26 accidents were all due to unsafe behaviors (violating regulations, command violations, etc.), 19 of the 26 accidents were not inspected and ventilated before the operation, and 6 were ventilated and not inspected. In 1 case, ventilation and testing were carried out, but the ventilation state was not maintained all the time. From the above results, it can be seen that there are many safety operating procedures for operations in limited space, and the requirements for implementation are relatively high. As long as there is a point that does not meet the requirements, it may lead to accidents.

6 direct causes of death

Of the 26 accidents, 15 were caused by inhalation of toxic gases such as hydrogen sulfide, 7 were caused by lack of oxygen, and 4 cases were not clearly identified as toxic gases or caused by lack of oxygen. It can be seen from the results that the risk of toxic environment is still significantly greater than that of hypoxic environment.

In April, the temperature in Beijing increased and the rain increased, and the safety risks of operations in limited spaces increased. The Beijing Municipal Emergency Management Bureau reminded all relevant units of the city’s limited space operations: to strengthen the construction of systems, regulations, and plans, and determine

Organize safety training, carry out emergency drills, improve employees’ safety awareness and self-rescue capabilities, equip operation and protective rescue equipment in accordance with regulations, supervise operators to implement safe operating procedures, and actively prevent poisoning and suffocation accidents in limited spaces.

In terms of protective equipment, Hanhai Opto-electronic recommends that operators in limited space choose laser absorption spectroscopy technology products to improve the accuracy and speed of gas detection during operation. For example, when performing operations or inspections in sewage wells (pools), power wells, thermal wells, gas wells, communication wells, and pipelines, Hanhai photoelectric telemeters can be configured. In this way, remote gas telemetry can be realized, and the detection personnel can be prevented from being injured when entering the gas leakage area.

Compared with the traditional gas monitoring equipment currently in use, Hanhai photoelectric telemeter has the following advantages:

high sensitivity:

With millisecond-level response speed, it can detect even small gas concentration changes in the first time, avoid missing reports, and achieve timely warning.

High monitoring accuracy:

The laser can achieve "fingerprint" detection, only responds to the target gas, can accurately reflect the real-time gas concentration distribution in the warehouse, without false alarms, and provide reliable and effective guidance for safety management.