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Interpreting the Key Contents of the Safety Technical Specifications for Work in Confined Spaces

On October 31, 2025, the State Administration for Market Regulation and the National Standardization Administration Committee released the “Safety Technical Code for Work in Confined Spaces” (GB46768-2025), which came into effect on May 1, 2026. The core content includes safety management, pre‑work safety technical requirements, in‑work safety technical requirements, post‑work safety technical requirements, verification methods, and more.

Confined spaces come in a wide variety of forms, are found across numerous industries, have unique structural characteristics, and often suffer from poor natural ventilation, making them prone to the accumulation of toxic, harmful, flammable, or explosive substances, or to oxygen deficiency. Performing work in confined spaces carries significant risks, easily leading to safety incidents such as poisoning, asphyxiation, and fire or explosion. Moreover, reckless rescue attempts after an accident can quickly escalate casualties and lead to severe consequences.

To curb the frequent occurrence of accidents during confined space operations, China has promulgated a series of regulations and standards related to confined space safety, which have played a positive role in practice. However, at present, China’s specialized laws and standards for confined space safety still fall short of meeting actual needs. First, there is a lack of national standards that cover confined space safety across all industries and all relevant fields. Second, some departmental standards are outdated, with certain provisions failing to align with or complement national and industry standards, leading to ongoing challenges. Third, according to the current “Standardization Law of the People’s Republic of China,” with the exception of national standards, industry standards and local standards are, in principle, only recommendatory—posing certain difficulties when it comes to effective implementation. Therefore, whether from the perspective of preventing confined space accidents, guiding and standardizing confined space safety management and operational practices, or strengthening oversight and enforcement of safe production in confined space operations, there is an urgent need to develop a comprehensive technical standard for confined space safety that covers all industries and all relevant fields.

The development of this standard will fill the gap in China’s lack of fundamental technical standards for confined space operations across the entire industry. The implementation of this standard will effectively guide organizations involved in confined space work to enhance their operational safety management, standardize work practices, and improve safe production conditions in confined space operations. At the same time, it will provide strong support for safety regulatory authorities at all levels in urging relevant entities to fulfill their primary responsibilities for safe production in confined space operations and in carrying out safety oversight work efficiently. This is of great significance for elevating the level of confined space operation safety in China, curbing accidents, and safeguarding the lives and safety of employees.

This article provides an interpretation of key contents from the “Safety Technical Code for Work in Confined Spaces,” including the definition and identification of confined spaces, the critical requirements for gas detection, the strict implementation of the principle “Ventilate first, then detect, and finally commence work,” the duties of supervisors, and the guideline “Do not attempt rescue blindly.”

I. Definition and Identification of Confined Spaces

Definition of a confined space: A space that is enclosed or partially enclosed, not designed as a permanent workplace, where personnel can enter to perform work, and which is prone to the accumulation of toxic or hazardous, flammable or explosive substances, or to insufficient oxygen levels.

The definition comprises four key elements:

1. Spatial characteristics: Enclosed or partially enclosed, meaning that connectivity with the external atmospheric environment is limited and air circulation is poor.

2. Design Purpose: It is not designed for continuous, long‑term operation; it is only occasionally accessed for maintenance, inspection, cleaning, and other similar tasks.

3. Accessibility: The head or entire body of a person can enter.

4. Hazards: Toxic and harmful gases (such as hydrogen sulfide and carbon monoxide), flammable and explosive gases (such as methane), or oxygen deficiency (below 19.5% by volume) may easily accumulate.

Common confined spaces include the following three categories:

1. Underground Structures: Such as basements, underground warehouses, underground projects, underground pipe trenches, culverts, tunnels, underpasses, pits, deep excavations, abandoned wells, cellars, inspection chambers, biogas tanks, septic tanks, and sewage treatment ponds, etc.

2. Above-ground types: such as distiller’s grains tanks, fermentation tanks, pickling tanks, pulp tanks, grain silos, and feed bins, etc.

3. Such as ship cabins, storage (tank) vessels, tank trucks, reaction towers (kettles), kilns, furnace chambers, flues, pipelines, and boilers, etc.

2. Key Requirements for Gas Detection

Gas detection is the most critical safety measure for confined space operations and must follow the principle of “ventilate first, then detect, and finally work.”

1. Pre‑testing Preparation:

Investigate and analyze the types of hazardous gases that may be present (do not conduct tests blindly). Stir up accumulated water, sediment, and material residues to ensure that hazardous gases are fully released (to avoid low concentrations during testing that increase upon entry).

2. Testing Items:

Required inspections: Oxygen, combustible gas, hydrogen sulfide, and carbon monoxide (four-in-one detector).

Targeted Testing: Based on other potentially present toxic and harmful gases in the working environment (such as ammonia, chlorine, carbon dioxide, benzene compounds, etc.).

3. Testing Method:

Use a pump‑suction gas detection alarm (not a diffusion‑type; pump‑suction devices can sample from a distance).

The inspectors are positioned upwind outside the confined space (to ensure the safety of the inspection personnel).

Detection direction: From top to bottom, and from near to far (because some gases are heavier than air and will settle at the bottom, while others are lighter than air and will accumulate at the top).

4. Testing Site Setup (Extremely Important):

Vertical directions (such as shafts and storage tanks): At least 3 measurement points— the top point no more than 1 m from the top, the bottom point no more than 1 m from the bottom, and intermediate points evenly spaced with a maximum spacing of 8 m.

Horizontal directions (such as pipelines and culverts): At least 2 points, with the near end located ≥0.5 m from the inlet and the far end located ≥2 m from the inlet.

When space is limited, the number of detection points can be appropriately reduced, but it must not fall below the prescribed minimum.

5. Passing Criteria (Must be met simultaneously):

Oxygen content: 19.5%–23.5% VOL (oxygen levels below 19.5% may lead to hypoxia, while levels above 23.5% pose an explosion risk); combustible gases: ≤10% LEL. Toxic and harmful gases: ≤ the maximum permissible concentration or the permissible concentration for short-term exposure.

6. Inspection Records:

The detection location, time, gas type, and concentration must be recorded accurately, signed for confirmation by the inspector, and filed for safekeeping.

7. Non‑conformance Handling:

Any failure to meet the standards will result in immediate suspension of work; mechanical ventilation must be carried out, followed by retesting until the requirements are met.

3. Strict Adherence to the Principle of “Ventilate First, Test Next, Then Work”

“Ventilate first, then test, and finally work” is the most fundamental and critical safety principle for confined space operations, which must be strictly followed and the order must not be reversed.

Step 1: Natural Ventilation:

On the upwind side outside the confined space, open the entrances and exits and other facilities that are connected to the external atmospheric environment (such as vents and exhaust ports).

Natural ventilation time: Generally no less than 30 minutes (determined based on the size of the confined space and the level of hazard).

Pay attention to safety when starting: Gas may surge out or liquids may splash—be sure to wear protective gear.

Step 2: Initial Gas Detection:

Perform initial gas detection after natural ventilation.

Step 3: Work Environment Assessment:

Based on the test results, determine whether the entry conditions are met: oxygen content between 19.5% and 23.5%, combustible gas ≤ 10% LEL, and toxic or hazardous gases ≤ the maximum permissible concentration or the short-term exposure limit.

Step 4: Mechanical Ventilation (if the initial inspection fails):

Use mobile mechanical ventilation equipment (such as axial fans and centrifugal fans) to supply clean air into confined spaces (pure oxygen or oxygen‑enriched air must not be used).

Ductwork Installation:

Single air inlet/outlet: The duct extends into the bottom for supply air (without touching the bottom, leaving space for airflow).

Multiple entrances and exits: Supply air near the workers and exhaust air away from the workers (forming an airflow channel).

Ventilation time: Determined based on the size of the space and the level of contamination, generally no less than 30 minutes.

Step 5: Conduct another gas detection and environmental assessment.

After mechanical ventilation, re‑testing is required; if the results are still unsatisfactory, ventilation must continue. The causes should be analyzed and targeted measures implemented, and entry into the work area is permitted only after passing the inspection.

Step 6: Maintain continuous ventilation during作业.

Continuous ventilation is required throughout the work process; mechanical ventilation must be maintained continuously in the following situations:

Those that fail the initial inspection.

Oxygen may be lacking during the work process.

During the work process, gas concentrations may suddenly increase.

Carrying out operations such as dredging, painting, waterproofing, anti-corrosion treatment, and welding.

Key points:

1. Pure oxygen or oxygen‑enriched air must not be used for ventilation, as excessively high oxygen concentrations (>23.5%) can significantly increase the risk of fire and explosion. Clothing, tools, and other materials are highly flammable in oxygen‑enriched environments; therefore, only clean compressed air or ambient air should be used.

2. Selection of Ventilation Methods

Natural ventilation: Suitable for confined spaces with low levels of hazard and good ventilation conditions.

Mechanical ventilation: Suitable for confined spaces with a higher degree of hazard, poor ventilation conditions, or where natural ventilation still fails to meet the required standards.

3. Verification of Ventilation Performance

You cannot rely on experience to determine whether ventilation is sufficient; you must verify the effectiveness of ventilation through gas detection.

Only those who pass the inspection are allowed to enter.

4. Duties of Guardians and the Principle of “Do Not Rescue Recklessly”

The guardian is the “lifeline” of confined space work safety, and the extent to which they fulfill their duties directly affects the life safety of the workers.

The core responsibilities of a guardian:

1. Continuous monitoring throughout the entire process

You must remain outside the confined space at all times (you may not leave), provide continuous supervision (you may not engage in other activities), and wear clearly visible identification (such as a “Supervisor” armband or vest).

2. Closely monitor

Monitor the operator’s work process (movements, status, and location), keep an eye on gas detection data (with real‑time monitoring to identify abnormalities), and maintain effective communication with the operator (through scheduled check‑ins and timely responses).

3. Timely Alerts

Immediately sound an evacuation alarm upon detecting any abnormalities and assist workers in evacuating the confined space. Abnormal conditions include: workers experiencing physical discomfort, gas detection alarms, equipment failure, or other hazardous situations.

4. Regional Control

Prevent unauthorized personnel from entering the work area, especially to stop those unfamiliar with the situation from accidentally trespassing.

The guardian’s “three no’s” principle:

1. Do not leave the work site.

Even brief departures are not permitted; if you need to leave, another qualified guardian must take over.

2. Entry into confined spaces for work is prohibited.

Once a supervisor enters the area, they lose their supervisory function; if something goes wrong with the worker, the supervisor will also be in danger.

3. Do not attempt rescue blindly.

In the event of an accident, caregivers must not enter to provide assistance without first taking proper protective measures. They must immediately activate the emergency response plan and carry out rescue operations only after ensuring hazard control and personal protection are in place; when necessary, they should request support from professional emergency rescue teams.

The deeper meaning of “do not attempt rescue blindly”:

A prominent characteristic of confined space accidents is “escalation of casualties”: what begins as an incident involving just one person in distress can quickly turn into a tragedy, as reckless rescue attempts lead to additional rescuers becoming trapped, ultimately resulting in mass fatalities and injuries.

Typical manifestations of reckless rescue:

Entering a confined space without wearing respiratory protection.

Entering a confined space without conducting gas detection.

Entering a confined space without taking ventilation measures.

Entering confined spaces without using safety ropes or other protective measures.

Multiple people enter to provide rescue at the same time.

The problem of reckless rescue efforts is particularly acute: nearly 80% of confined space work accidents result in increased casualties due to indiscriminate rescue attempts, and more than 50% of fatalities are rescue workers. Therefore, reckless rescue must be strictly prohibited to prevent the escalation of injuries and deaths.

The correct approach to scientific rescue:

Immediately activate the emergency response plan.

Call the police immediately (119, 120, or the company’s emergency response team).

Take measures outside the confined space (such as improving ventilation or calling for the workers).

If entry is necessary, you must wear a self‑contained breathing apparatus, secure a safety rope, and have someone outside to provide guidance and support.

Only one person should enter to provide rescue at a time, and someone must remain outside to supervise and provide assistance.

Wait for the professional emergency rescue team to arrive.

Rescue methods include non-entry rescue and entry rescue:

Non‑entry rescue refers to a rescue method in which rescuers, from outside the confined space and using relevant equipment and tools, safely and quickly remove trapped personnel from the confined space. Non‑entry rescue is a relatively safe rescue approach, but it must meet at least the following two conditions simultaneously:

1. The person trapped in the confined space was wearing a full-body harness and was securely connected to a tether point outside the confined space via a safety rope.

2. The location of the person trapped in the confined space must be unobstructed and free from any barriers between their position and the entrance/exit of the confined space.

When the trapped person is not wearing a full-body harness, has no safety rope connected to an anchor point outside the confined space, or when non‑entry rescue cannot be carried out due to the trapped person’s location, rescuers must enter the confined space to perform the rescue.

Entry-based rescue operations carry significant risks; if rescuers fail to properly implement protective measures, casualties are highly likely to escalate. Therefore, when conducting entry-based rescue, rescuers must adopt scientifically sound protective measures to ensure their own safety and effectiveness. For example, rescuers must wear positive-pressure air respirators, full-body harnesses, hard hats, and other personal protective equipment before entering the site—and it is strictly prohibited to carry out entry-based rescue without proper protection!