Occupational Safety Training Materials for Working in Confined Spaces

DOWNLOAD THE OCCUPATIONAL SAFETY DOCUMENT SUITE (6 GROUPS, OVER 300 INDUSTRIES)

The document for the occupational safety training course in confined spaces equips workers with safety knowledge for working in tunnels, sewers, tanks, and other narrow spaces – places where there is always a potential risk of oxygen deficiency or toxic gas contamination.

Chapter 1: Overview of Confined Spaces

1. Definition in the Confined Space Safety Document

A confined space is an enclosed or partially enclosed area large enough for a worker to enter. This space is not designed for continuous human occupancy, but workers may enter it to perform tasks such as inspection, cleaning, maintenance, and repair. The small or obstructed entry/exit can make it difficult to get in and out and can complicate rescue efforts in an emergency.

---

2. Characteristics

• Entering confined spaces can be very dangerous.
• A worker is considered to have entered a confined space as soon as their head passes through the entrance plane.
• If the confined space contains toxic gases, a worker can be at risk just by being near the entrance. These toxic gases are often under high pressure and temperature.
• Only individuals trained in confined space safety are permitted to work in these areas. Proper procedures and protective equipment are required before entry.

---

3. Classification

• Type 1
  • A Type 1 confined space has a high potential risk from various contaminants that are not easily identified or controlled. The following conditions may be present in a Type 1 space:
  • The attendant outside must also wear a self-contained breathing apparatus (SCBA) for rescue purposes in case of an incident.
• Type 2
  • A Type 2 confined space has a high potential risk from identified contaminants. Type 2 confined spaces are not for frequent entry, although conditions can be controlled before entry. The following conditions may be present in a Type 2 space:
    • Known flammable or explosive gases.
    • Contaminant sources that can be controlled.
    • Controllable or predictable inflow of liquids.
    • Poor ventilation.
    • Restricted entry and exit.
• Type 3
  • A Type 3 confined space is usually isolated from potential hazard sources. These confined spaces are entered frequently under controlled conditions. The following conditions may be present in a Type 3 space:
    • Contaminants are isolated.
    • Detection of contaminants is controlled.
    • Sufficient lighting.
  • When working, continuous monitoring must be conducted in a Type 3 confined space, and personal protective equipment must be used.
• Type 4
  • A Type 4 area has a very low potential atmospheric risk. Entry and work in this type of confined space must be performed in accordance with safety procedures. Typically, Type 4 confined spaces have:
    • Unrestricted entry and exit.
    • Good ventilation.
    • Predictable and controlled low-risk contaminants.
    • Good lighting.
  • The supervisor is responsible for ensuring that the air in this type of enclosed area cannot become contaminated or oxygen-deficient.

---

4. Common Confined Spaces

Tanks, vats, furnaces, tunnels, silos, pipelines, sewers, storage bins, pits, reservoirs, water tanks.

---

Chapter II: Hazards in Confined Spaces and Responsibilities of Stakeholders

I. Hazards in Confined Spaces

1. Oxygen in the confined space safety document

• Oxygen deficiency is the leading cause of death for workers in confined spaces. Low oxygen levels cannot be detected by sight or smell. We must measure the air in the confined space to know the hazardous condition. Very low air levels can cause brain damage and cardiac arrest in just a few minutes.
• Causes of oxygen deficiency:
  • Oxygen is consumed when metal rusts.
  • Oxygen is consumed during combustion – such as with propane heating, during cutting or welding, and when internal combustion engines are running.
  • Oxygen can be displaced by other gases – such as welding gases or gases pumped into the space to prevent rust.
  • Microorganisms consume oxygen – such as in sewers and fermentation tanks.
  • Too much oxygen is not as common a hazard as too little oxygen, but it is also dangerous. Excess oxygen increases the risk of fire or explosion in an enclosed space. Common materials that would not normally ignite or burn in normal air can ignite very quickly and easily in an oxygen-rich environment.
• How to check the oxygen concentration in a confined space
  • Use an oxygen monitor
    • A trained person must use the monitor to test the air before anyone enters the confined space.
    • The oxygen monitor shows the oxygen level as a percentage of the air. Air contains 20.92% oxygen.
  • Note
    • As altitude increases, the oxygen concentration in the air decreases. However, the reading on the monitor is not affected by changes in altitude. Therefore, always consult a qualified professional to determine safe entry procedures.
    • Clean outside air contains 20.92% oxygen. If the air inside the confined space differs from 20.92%, a qualified professional must investigate the cause to ensure the space is safe. It is crucial to understand what is causing the change in oxygen levels. The cause must be known before workers are allowed to enter the space. For example, many toxic gases pose a high risk to workers even at low concentrations that displace very little oxygen. With some common solvents, a 0.1% change in the oxygen reading could mean there is enough toxic gas to cause death or serious injury.
    • Working in an atmosphere with an oxygen level between 14% and 17% can impair judgment, cause dizziness, fatigue, and fainting. At even lower oxygen levels, breathing may provide so little oxygen that a person’s muscles will not respond, and they will not have enough strength to escape, even if they are still conscious. The only safe way is to determine if the air in the confined space has enough oxygen.
• Workers must not enter a confined space with less than 19.5% oxygen without taking precautions, including the use of a supplied-air respirator.

2. Toxic Atmosphere in the confined space safety document

• Airborne contaminants can create a toxic atmosphere for workers and can cause injury or death.
• The concentration of substances inside the confined space must be determined with an air monitor that is properly sized and calibrated. An air monitor can provide an audible alarm to workers before the permissible exposure limit is reached.
• In most cases, mechanical ventilation systems such as fans must be used to ventilate the space and introduce clean air. In addition, the hazardous substance must be removed whenever possible. Air testing and ventilation are the best ways to ensure workers are not at risk from a hazardous atmosphere.
• At certain concentrations, some substances become immediately dangerous to life and health (IDLH). At these levels, even brief exposure can have permanent health effects such as brain, heart, or lung damage. Or the substance could make workers dizzy or unconscious, preventing them from escaping the confined space. Some substances have very low IDLH levels. For example, the IDLH level for hydrogen sulfide is only 100 ppm (parts per million).
• Some causes of a toxic atmosphere
  • Due to specific liquids in the confined space
    • Liquids can create a hazardous atmosphere if they evaporate. For example: Liquid fuel in a tank can evaporate. Hazardous conditions can arise when gaseous parts of waste materials are disturbed during cleaning. It could be an organic material that decomposes and can release toxic H2S gas when cleaning a manure pit. Decomposing sludge in functional tanks also produces H2S gas. Or grain in a silo that ferments will consume oxygen and produce toxic gases.
  • Due to the work being done inside the confined space.
    • In one-third of accidents involving toxic gases or oxygen deficiency, there was no hazard in the confined space when workers first entered. It was the work inside the confined space that created the hazardous atmosphere. Activities that can release hazardous substances into the air include grinding, scraping, removing insulation, metal spraying, rubber lining, painting, cutting, welding, and using internal combustion engines. Cleaning agents can be toxic, can react with residue in the tank, or can release deadly gases from absorbent surfaces in the space.
  • Due to contamination from external sources: The confined space may be located next to a source of hazardous materials. Contamination can enter the confined space through permeable walls, such as sewer or pit walls, or openings that are difficult to seal, such as conduits. Often, a mechanical ventilation system is installed to bring outside air into the confined space. If the air intake duct is placed next to a running vehicle or equipment, or a chemical source, the duct will draw that gas into the confined space.

3. Explosive Atmosphere in the confined space safety document

Three elements are required for a fire or explosion to occur: Oxygen, a flammable material (fuel), and an ignition source.

• Oxygen
  • Normal air contains 20.92% oxygen, which is sufficient for combustion. However, higher oxygen levels increase the flammability of materials. Air is considered oxygen-enriched when it exceeds 23%. This increase can be caused by improperly sheathed oxygen lines, ventilating the space with oxygen instead of air, or leaking welding equipment.
• Fuel
  • Fires and explosions in confined spaces are often caused by flammable gases and vapors. Coal dust and grain dust can explode when the amount of dust reaches a certain level in the air.
  • Note:
    • Fuel containers such as gasoline and propane gas should not be brought into a confined space because the fuel can easily ignite or explode.
    • Two or more chemicals can react with each other to cause an explosion.
  • Some gases that can explode or burn in a confined space.
    • Acetylene gas from leaking welding equipment.
    • Methane and H2S gases released from organic waste materials in sewers or tanks.
    • Hydrogen gas generated when aluminum or galvanized metal comes into contact with corrosive liquids.
    • Grain dust, coal dust.
    • Solvents such as acetone, ethanol, toluene, turpentine, and xylene, which may be present in a confined space due to spills, improper use, or disposal.
  • A trained person must test the atmosphere for flammable or explosive gases and vapors before entering a confined space. Hazardous gases and vapors are not always visible or smellable. If a potentially explosive atmosphere is detected, a qualified person must evaluate the air to ensure that entry into the confined space is safe.
• Ignition sources
  • Ignition sources include: Open flames, welding sparks, hot surfaces, lights, sparks from metal-on-metal contact, electric motor sparks, static electricity, and chemical reactions.

CONTAMINANT	WHAT IS THE MAIN HAZARD	WHAT DOES IT LOOK/SMELL LIKE?
Argon (Ar)	Displaces oxygen, Can accumulate at the bottom	Colorless, odorless
Carbon dioxide (CO2)	Displaces oxygen, Toxic	Colorless, odorless
Carbon monoxide (CO)	Toxic – asphyxiant (suffocating)	Colorless, odorless (NO WARNING)
Chlorine (CL2)	Toxic – irritates lungs and stings eyes, Can accumulate at the bottom	Yellowish-green; pungent odor
Gasoline vapor	Fire and explosion, Can accumulate at the bottom	Colorless; sweet odor
H2S	Very flammable, Very toxic – damages lungs, Can accumulate at the bottom	Colorless; rotten egg smell
Methane (CH4)	Fire and explosion, Can accumulate at the top	Colorless, odorless (NO WARNING)
Nitrogen (N2)	Displaces oxygen	Colorless, odorless (NO WARNING)
Nitrogen dioxide (NO2)	Toxic – severe lung irritant, Can accumulate at the bottom	Reddish-brown; heavy odor
Sulfur dioxide (SO2)	Toxic – severe lung irritant, Can accumulate at the bottom	Colorless; foul, suffocating odor
Oxygen (O2)	Low level – asphyxiation, High level – immediate ignition, explosion	Colorless, odorless

 

4. Loose and Unstable Materials

• Whenever unstable solid materials composed of small particles, such as sand, are stored in a confined space, there is a risk of the material collapsing onto workers, trapping or burying them. Examples of these confined spaces include sand bins, wood chip or sawdust bins, grain storage silos, etc.
• Wherever there is loose, unstable material that could trap or bury you, a qualified person must inspect and assess the hazards. Do not enter until the hazards have been eliminated or controlled. Specific training and safety precautions must be applied before you enter.

5. Slips, Trips, and Falls Hazards.

• Confined spaces may have an opening that is difficult to squeeze through, and a ladder to climb up or down. Therefore, there is a risk of falling while entering the space as well as while inside. In addition, tank floors or other wet environments or ladder rungs can be very slippery.
• If this hazard cannot be eliminated and there is a risk of falling from a height, a fall protection system (such as guardrails or a harness and lifeline) may be required.

6. Falling Objects in the confined space safety document

• In a confined space, there may be a risk of being struck by falling objects such as tools or equipment, especially when entry points or workstations are located above workers.
• If workers may face the risk of falling objects, safe work procedures must be implemented to prevent this. For example, scheduling work so that no worker is working above another, and lowering equipment and tools before workers enter and removing them after workers leave.

7. Electric Shock

• Electric shock can be caused by damaged power cords, welding cables, or other electrical equipment. Working in enclosed metal spaces or in wet conditions can be very dangerous. Install a ground-fault circuit interrupter (GFCI) or use a solid ground wire when there is a risk of electric shock. All electrical sources that pose a hazard to workers inside the space must be locked out according to the written lockout procedure for that confined space.

8. Substances Entering Through Pipes

• Pipes near a confined space may contain liquids, gases, or other hazardous substances. If these substances enter the confined space, the following hazards may exist:
  • Toxic gases
  • Burns from hot substances
  • Drowning
  • Being trapped, crushed, or buried
• The entry of substances through pipes into the confined space must be prevented. This is done by “isolating” the pipe from the confined space. This method usually involves removing sections of pipe or using special blanks to block the pipe from the confined space. If valves are used to isolate the pipe, a special double block system must be used so that nothing can leak into the confined space. In special cases, a qualified person may certify that the valve isolation system is safe for workers to perform the intended work in the confined space.

8. Poor Visibility.

• Poor visibility increases the risk of accidents and makes it more difficult for someone to see a worker in distress. If poor visibility is due to insufficient lighting, the lighting level should be increased (although it is not always necessary to illuminate the area). If activities such as sandblasting or welding cause poor visibility, adequate ventilation may be needed to reduce airborne contaminants.

If portable lighting is used where there may be an explosive atmosphere, the light must be “explosion-proof.” Emergency lighting such as flashlights or battery-operated area lights should be provided when necessary so that workers can locate exits and escape routes.

9. Extreme Temperatures in the confined space safety document

• Special precautions are required before workers enter equipment such as boilers, reactors, and low-temperature systems. A qualified person must provide these measures. Allow sufficient time for confined spaces that have been steam-cleaned to cool down.

10. Noise

• Noise in a confined space can be very hazardous because it reflects off the walls. The noise level from a source inside a small confined space can be up to 10 times louder than the same source outdoors. If the noise level cannot be reduced, appropriate hearing protection must be worn when necessary.

11. Drowning Risk

• Confined spaces should be drained or dry when entered. Areas that are not drained or dry may pose a drowning risk. The risk of drowning in a tunnel or tank with a lot of liquid is easy to recognize. However, workers have also drowned in puddles of liquid. For example, oxygen deficiency, toxic gas, or a blow to the head can cause a worker to become unconscious. The worker falls face down in a small puddle of water and drowns.

---

II. Responsibilities of Stakeholders

1. Responsibilities of the Supervisor

• The supervisor or foreman must strictly manage the work environment with the following specific responsibilities:
• Conduct a job safety analysis to identify potential hazards associated with the work to be performed.
• Prepare adequate personnel, equipment, and safety means necessary to perform the work.
• Ensure that the concentration of oxygen and explosive substances in the confined space is checked and closely monitored.
• Ensure that workers are aware of and comply with safety procedures and regulations when working in confined spaces.
• Ensure that all workers are in good health and are trained to be able to perform and complete the work.
• Ensure that the Confined Space Entry Permit is fully completed. The work permit is valid for 12 hours and if the work continues.
• Ensure that warning signs, an attendant outside, rescue and firefighting equipment, ventilation, and communication systems are maintained throughout the work process.
• Upon completion of the work, when closing the workplace, the supervisor must check to ensure that no one is left inside and that all equipment, tools, and materials are cleaned up.

2. Responsibilities of the worker when entering to work in a confined space.

• Ensure they are in good health and trained to be able to perform the work, and are aware of the potential hazards through the job safety analysis to be performed.
• Ensure strict compliance with safety regulations and procedures when working in the confined space and sign the Work Permit before starting the work.

---

Chapter III. Preparation Steps Before Entering a Confined Space and Safety Requirements and Principles

I. Preparation Steps Before Entering a Confined Space

1. Implement isolation measures

• Implement isolation measures for the confined space to prevent external impacts such as pressure, temperature, or other energy sources. Specifically:
  • Isolate electrical sources.
  • Deactivate control device switches.
  • Bleed pneumatic and hydraulic lines, and disconnect mechanical linkages on equipment such as control shafts where possible.

2. Conduct gas testing

• Gas testing must be conducted by a trained person, always prioritizing external measurement methods. Because many gases are heavier than air and will settle at the bottom of the confined space, and some gases are lighter and will float at the top. Therefore, it is necessary to test all locations (top, middle, bottom) of the confined space with an accurately calibrated testing device.

• Important
  • Never trust your senses to determine that the air in a confined space is safe, as you cannot see or smell to detect toxic gases, nor can you determine the existing oxygen level.
  • Do not use a lighter or open flame for inspection before gas testing.

3. Ventilation in the confined space safety document

 

• Ventilation with a blower fan is essential to remove toxic gases or vapors from inside the confined space. Typically, for ventilation, we use a fan to blow air from the outside into the confined space. Ventilation requires ensuring that the intake air is clean and that as many air outlets as possible are opened in the confined space.
• There are many ventilation methods; the method and equipment used depend on the size of the entrance to the confined space and the available air supply.
• If ventilation into the confined space is not possible, workers can use gas masks or self-contained breathing apparatus.

4. Plan for emergency response

• The rescue plan must be approved by everyone involved in the work. The requirements for equipment, systems, or auxiliary measures in the plan must be fully met before work begins.

5. Prepare emergency rescue tools and equipment

• Emergency rescue tools such as breathing apparatus, rescue ropes, lights, stretchers, and other first aid equipment.

6. Assign a person to watch outside the manhole or exit

• This person must have first aid skills and be able to communicate with relevant parties. This person must not leave their post as long as anyone is working inside the confined space. This person is also responsible for recording the name and time of each person entering and exiting the confined space.

7. Tools for working in a confined space

• must be considered; equipment that is flammable or explosive must not be used. If working in a potentially explosive environment, all tools used must be non-sparking or intrinsically safe according to explosion-proof standards.
• Workers in confined spaces must always wear full personal protective equipment, and a safety line must be connected to an area outside the workplace.
• Only low-voltage electrical equipment under 12V should be used when working in metal tanks or wet areas.

---

II. Requirements when working in a confined space

1. An attendant must always be present outside and maintain communication with the person working inside.
2. Always monitor the concentration of toxic gases and Oxygen (ensure Oxygen is between 19.5% – 23.5%) (International), QCVN No. 34/2018.
3. Monitor the temperature in the work area.
4. Safe and adequate lighting system.
5. Exits are always ready.
6. Ventilation system is always ensured.
7. Always control the use of chemicals in the work area.
8. When the work is finished, ensure the number of workers who entered equals the number who exited.

---

III. Safety rules for working in a confined space

1. Workers must be safety-trained and in good health.
2. Before entering a confined space, they must be:
   • Informed about the microclimate, equipment, and goods.
   • Briefed on the work methods.
   • Must use all necessary personal protective equipment.
3. Open all hatches in the confined space, and ventilate the air inside.
4. Re-check the concentration of air and toxic gases/vapors.
5. Do not have many people enter the confined space at the same time; the first person to enter must wear a lifeline.
6. There must be an attendant outside the confined space or a sign posted that says “person working in confined space” while work is in progress.
7. Electric welders working in a confined space must have adequate personal protective equipment such as insulated shoes, boots, gloves, etc., and follow safety measures.
8. Movement in and out of the confined space must follow regulations.
9. Lighting in a confined space must use 12V voltage.
10. Confined spaces containing flammable or explosive substances must use specialized explosion-proof tools and equipment. Regularly check and prohibit bringing lighters, matches, or oil lamps.
11. Continuously implement ventilation measures for work that regularly generates toxic gases/vapors.
12. When working in manholes, tunnels, sewers, etc., there must be barriers, warning signs, and an attendant outside to prevent others from falling in or throwing objects in.

---

IV. Work Procedure in a Confined Space

---

Chapter IV: Escape and Rescue Guide

• Immediately notify others in the work group in the enclosed area and the attendant of the emergency and the need for rescue. When the attendant is unaware of the group’s status OR the cause of the injury OR cannot communicate, the environment must be considered hazardous, and the hazardous environment rescue procedure must be followed.
• The attendant immediately notifies emergency services.
• Always perform emergency rescue via the fastest and safest route. Identify and isolate the hazard if it can be done safely.
• The enclosed area can only be entered if it has been made safe by:
  • Using personal breathing apparatus
  • Isolating the hazard
  • Having attendants outside
• And having all rescue equipment, including ventilation equipment if necessary. The emergency response is applied even in an emergency situation to perform resuscitation, provide first aid, or rescue.
• In the initial response when emergency rescue is needed, standard rescue techniques will be applied by trained personnel.
• If possible, a person needs the emergency services team to provide necessary instructions.
• Immediate action in an emergency, such as entering the enclosed area immediately for rescue, can lead to more casualties – not only to those needing rescue but also to those attempting the rescue.
• Upon escape, the permit holder will do a head count of everyone.
• Re-entering the enclosed area to retrieve tools and equipment is only permitted when the atmosphere has been tested and the area has been made safe.
• The permit holder will submit an incident/injury investigation report to the project manager.

---

Chapter V: Further Reference

1. Group 3 Safety Training and Certification Service

---

2. Group 3 Occupational Safety Test

• Group 3 Occupational Safety Multiple Choice Test

---

3. Price List for Occupational Safety Training Services

• See details

---

4. Download the document

• Download the occupational safety document for confined spaces