Confined Space Hazards: Managing The Risks Of Working In Confined Spaces

working in confined spaces

Confined spaces are common in many industrial settings, from construction sites to chemical plants. These environments pose significant risks due to their restrictive nature and potential exposure to hazardous conditions. Understanding these risks and implementing strict safety protocols is crucial to protect workers who must enter these spaces. This article discusses what confined space refers to, defines what a required confined space permit space is, and explores safety strategies and rescue procedures to prevent serious injury when entering a confined space.


What Is A Confined Space?

A confined space, as defined by the Occupational Safety and Health Administration (OSHA), is any enclosed or partially enclosed space that is not designed for continuous human occupancy, has limited or restricted means for entry or exit, and can pose serious hazards to workers entering the space. These spaces are often uncomfortable and potentially dangerous due to their design and the type of work performed within them. Some examples of areas considered confined spaces include:

  • Utility vaults
  • Pits
  • Manholes
  • Tunnels
  • Equipment housings
  • Pipelines
  • Silos
  • Sewers

Key Characteristics of Confined Spaces

Confined spaces are unique in their structure and potential hazards. The primary characteristics that define these spaces include:

  • Limited Entries and Exits: The entrances and exits of confined spaces are typically narrow, which can complicate both routine and emergency egress and ingress. For example, manholes, ducts, and crawl spaces have limited openings, making it challenging for equipment and rescuers to reach someone quickly during an emergency.
  • Not Designed for Continuous Occupancy: These spaces are generally designed for storage, processing, or accessing equipment for maintenance rather than for workers to stay for extended periods. Examples include underground vaults, tanks, and silos, where tasks are usually brief but require entry for specific operational or maintenance reasons.
  • Potential for Hazardous Atmospheres: Confined spaces often contain or have the potential to contain a hazardous atmosphere. This could be due to the presence of toxic chemicals, flammable gasses, or insufficient oxygen. For instance, a tank previously used to store chemicals may have residual vapors, or a poorly ventilated pit might have dangerously low levels of oxygen.
  • Engulfment Hazards: Some confined spaces pose risks of engulfment where an individual could be swallowed up by materials such as grains, sand, or other similar substances. This is particularly common in silos or bins used in agricultural or industrial settings.
  • Other Physical Hazards: Depending on their specific use or design, confined spaces may also present physical hazards such as unguarded machinery, exposed live wires, or heat stress conditions which are exacerbated by poor ventilation.

Confined Spaces Standards and Regulations

Standards and regulations governing confined spaces ensure safety and health in industrial workplaces. These regulations are designed to protect workers who may be exposed to dangerous conditions while working in confined spaces. 

OSHA 29 CFR 1910.146 Specifies requirements for permit-required confined spaces in general industry, focusing on safety procedures and worker protection
OSHA 29 CFR 1926 Subpart AA Provides guidelines for confined spaces in construction, addressing unique hazards specific to construction activities.
NFPA 350 Offers guidance on safe confined space entry and work, aiming to provide best practices beyond compliance.
ANSI Z117.1 Establishes safety requirements for entering, working, and exiting confined spaces at normal atmospheric pressure.
ISO 9001 Focuses on quality management systems which can include safety protocols such as those for confined spaces under operational risk management.
ISO 45001 A framework for occupational health and safety management systems, improving safety and reducing workplace risks, applicable to confined spaces.


10 Major Confined Space Hazards

confined space hazards info

Building on our understanding of what a confined space is and the regulations that govern them, it's crucial to recognize the physical and atmospheric hazards that can make these environments dangerous. Awareness and preparedness are key to managing these risks effectively. Hazards associated with confined spaces include:

  1. Atmospheric Hazards - Atmospheric hazards in confined spaces include toxic gasses, vapors, or insufficient oxygen levels. These hazards arise from both the nature of the stored materials and the external environment. Exposure to harmful gasses can lead to health complications, unconsciousness, or death. Oxygen-deficient environments can cause asphyxiation rapidly.
  2. Electrical Hazards - Electrical hazards occur due to exposed wires, conductive materials, or operational electrical equipment within the confined space. Electrocution or electrical burns are significant risks, particularly in wet conditions or where protective measures like grounding are not in place.
  3. Chemical Exposures - Workers in confined spaces may be exposed to hazardous chemicals in the form of solids, liquids, or gasses, which can be part of the process materials or residues. Chemical burns, poisoning, and long-term health effects such as cancer or organ damage can occur depending on the toxicity and exposure level.
  4. Access Restrictions - Confined spaces often have limited access, which can impede both entry and exit in emergencies. Delayed emergency response and difficulty in rescuing or evacuating workers quickly, increasing the severity of any incident that occurs.
  5. Fire - The risk of fire is elevated in confined spaces due to limited ventilation, which can enhance the flammability of materials and gasses. Fires in confined spaces are particularly dangerous due to rapid spread and intense heat, compounded by difficulties in escape and firefighting.
  6. Flood - Flooding can occur in confined spaces from internal sources like pipe bursts or external sources like heavy rainfall. Drowning, hypothermia, and exposure to water-borne contaminants are primary concerns, along with potential damage to equipment.
  7. Excess Oxygen - High levels of oxygen in a confined space can be as dangerous as low levels, particularly due to the increased risk of fire and explosion. Elevated oxygen levels can cause materials that are normally non-flammable to ignite easily and burn intensely.
  8. Explosions - Confined spaces can accumulate flammable gasses, vapors, or dust, which can lead to explosions if ignited. Explosions can cause severe injury or death and significant structural damage, complicating rescue and recovery efforts.
  9. Temperature - Extreme temperatures, either high or low, are a common hazard in confined spaces, influenced by external conditions or internal operations. Heat can lead to heat stroke and dehydration, while cold conditions can cause hypothermia and frostbite.
  10. Dust - Accumulation of combustible dust in confined spaces is a significant hazard, particularly in industries dealing with grains, flour, or certain metals. Combustible dust can lead to respiratory issues or, more critically, dust explosions.


Confined Space Requirements: Safety Protocol Key Elements

confined space sign

Having identified the major hazards associated with confined and enclosed spaces, it's essential to discuss the safety protocols that mitigate these risks. Effective safety management in confined spaces hinges on thorough planning, competent personnel, and strict adherence to safety standards and procedures. This section will outline the critical elements of safety protocols necessary for confined space operations.

Competence, Training, Supervision, and Suitability

Safety in confined spaces starts with ensuring that all personnel involved are competent and well-trained. This includes not just the workers entering the space but also those supervising and involved in rescue operations. This emphasizes the need for comprehensive training that cover critical aspects such as hazard recognition, equipment use, emergency procedures, and specific job tasks.

In addition, adequate supervision must be provided to ensure that safety procedures are followed meticulously. Supervisors need to be experienced and capable of recognizing early signs of trouble. Furthermore, it is crucial to evaluate the physical and psychological suitability of workers for working in confined spaces. This includes assessing their ability to wear required personal protective equipment and perform tasks under physically constrained and potentially stressful conditions.

Permit-to-Work Procedure

The permit-to-work is a formal written system used to control work in confined spaces and ensure that all elements of the safety protocol are in place before entry is allowed. Permit space must follow the following confined space regulations:

  • Clear Description of Work: The permit must clearly describe the work to be done, the hazards involved, and the measures to mitigate these hazards.
  • Safety Checks: Before a permit is issued, a series of safety checks must be completed. This includes testing atmospheric conditions, ensuring all equipment is functional, and confirming that emergency procedures are set.
  • Sign-off by Authorities: The permit must be signed off by the designated safety officer or supervisor. This signifies that all safety measures meet the required standards and that it is safe to proceed.
  • Time Bound: Permits are strictly time-bound. They are only valid for the duration of the specific job or shift and must be renewed for additional work.
  • Closure and Review: Once the task is completed, the permit should be formally closed with a debrief and review to ensure any learning points are captured and future safety is enhanced.

Gas Purging and Ventilation

Gas purging and ventilation are critical procedures designed to mitigate atmospheric hazards in confined spaces. Enclosed spaces produce dangerous air contaminants that pose risks of asphyxiation, fire, or explosion. This process ensures that harmful gasses in the atmosphere are removed and replaced with fresh air, minimizing risk and ensuring safe air circulation in the area. This involves displacing hazardous gasses and vapors from the confined space with an inert gas, typically nitrogen, with the goal to minimize the oxygen level to prevent combustion and to eliminate any toxic substances from the atmosphere.

Dangerous Residues

Dangerous residues, whether chemical, biological, or radiological, can pose severe health risks to individuals entering confined spaces. Before entry, all residues must be identified, and their potential hazards assessed. This includes understanding the chemical nature of residues and their possible reactions.

Whenever possible, residues should be removed or neutralized before entry. If removal is not feasible, appropriate protective measures must be taken to safeguard workers from exposure. In addition, appropriate PPE must be worn by all entrants to protect against specific hazards posed by the residues. This might include respirators, gloves, and chemical-resistant clothing.

Testing and Monitoring of the Atmosphere

Testing and monitoring the atmosphere in confined spaces are essential to detect invisible threats such as toxic gasses, explosive limits, and oxygen deficiency or enrichment. Before entry, the atmosphere should be tested from outside the confined space using portable gas detectors to determine if it is safe to enter. The atmosphere in a confined space should also be continuously monitored to alert workers of any changes in atmospheric conditions that could indicate developing hazards.

Mechanical, Electrical, and Process Isolation

Isolation of mechanical, electrical, and process systems is essential to prevent unintended energization or release of hazardous substances into confined spaces. Mechanical isolation involves physically disconnecting machinery and equipment from their power sources, typically through lockout/tagout (LOTO) procedures, to prevent accidental startup. Electrical isolation is achieved by disconnecting electrical power entirely and locking out the switches while process isolation involves closing and locking valve systems to prevent the flow of gasses, liquids, or solids into the confined space.

Respiratory Protective Equipment (RPE)

In environments where ventilation is insufficient to ensure breathable air, Respiratory Protective Equipment is crucial to protect workers from inhaling harmful contaminants.

  • Air-Purifying Respirators: Suitable for environments where the air quality is compromised but contains enough oxygen to breathe safely. These respirators use filters or cartridges to remove contaminants.
  • Air-Supplying Respirators: Used in oxygen-deficient atmospheres or where unknown hazards exist. These include self-contained breathing apparatus (SCBA) or airline respirators that provide a safe, external source of breathable air.
  • Fit Testing and Maintenance: Regular fit testing is essential to ensure a tight seal and effective protection. Maintenance, cleaning, and storage of RPE must follow manufacturer guidelines to ensure their reliability and performance.

Other Personal Protective Equipment (PPE)

While respiratory protection is critical, other types of PPE are equally important to ensure the safety of workers from head to toe. This includes the use of protective clothing from head to toe, eye and face protection, hearing protection, and head protection to ensure worker health and safety while working in confined spaces.

Safe Use of Work Equipment

In confined spaces, the correct and safe use of work equipment is crucial not only for the task at hand but also for the safety of the workers involved. All equipment used in confined spaces must be specifically suitable for the intended tasks and the environmental conditions of the space. These should also be regularly inspected and maintained according to manufacturer's guidelines to ensure it remains in safe working condition. Furthermore, workers must receive thorough training on the correct use of each piece of equipment.


Robust communication systems are essential in confined spaces due to the isolation of these areas and potential barriers caused by structural elements. Strategies often include the use of reliable two-way communication devices that can operate effectively in confined settings if necessary to maintain constant contact between the workers inside and the team outside, the establishment of predetermined emergency communication plans, and the implementation of regular check-ins during operations.

Access and Egress

Safe access to and egress from confined spaces is vital to ensure the safety of workers, especially in emergencies. Entry points should be large enough to allow workers to enter and exit easily, and accommodate the safe passage of rescue equipment if necessary. Ensure that pathways to and from the entry points are secure and free of obstructions to facilitate quick evacuation or rescue operations.


Confined Space Hazards: Control and Management

Effective management and control of confined space hazards require a strategic approach that combines thorough risk assessments, the right tools and equipment, and adherence to best safety practices. This comprehensive approach ensures that risks are minimized and worker safety is prioritized.

Confined Space Risk Assessment

Risk assessment is the first and most critical step in confined space safety management. It involves identifying potential hazards, evaluating the risks associated with these hazards, and determining appropriate control measures. This process involves:

  1. Identification of Hazards: Review all activities and conditions in the confined space that could potentially harm workers, such as toxic substances, oxygen deficiency, or fire risks.
  2. Risk Evaluation: Assess the likelihood and severity of each identified hazard impacting workers, considering existing control measures.
  3. Implementation of Controls: Based on the risk evaluation, implement control measures to eliminate or minimize risks. This may involve engineering controls, administrative controls, or personal protective equipment.
  4. Review and Update: Regularly review the risk assessment to ensure it remains up-to-date with changes in work processes, equipment, or regulations.

Confined Space Safety Tools and Equipment

Having the right tools and equipment is essential for ensuring the safety of workers operating in confined spaces. This includes not only personal protective and emergency equipment but also devices designed to control hazardous energies and inform personnel of potential dangers.

  • Gas Detectors - Essential for continuous monitoring of atmospheric hazards such as toxic gasses, flammable vapors, and oxygen deficiency. These detectors can provide early warning alerts to prevent health risks or fatal incidents.
  • Ventilation Equipment - Portable mechanical ventilation systems help maintain breathable air quality and can be crucial in removing or diluting hazardous atmospheres within confined spaces.
  • Personal Protective Equipment (PPE) - Comprehensive PPE may include respirators, protective suits, gloves, helmets, and boots, tailored to protect against specific hazards identified in the risk assessment.
  • Communication Devices - Devices that are intrinsically safe and capable of maintaining clear communications in environments with structural interferences are vital for coordinating operations and ensuring safety in emergencies.
  • Rescue and Emergency Equipment - Equipment such as rescue tripods, winches, and retrieval lines are critical for providing a means of rapid extraction in case of an emergency, ensuring that rescue operations can be executed swiftly and safely.
  • Lockout/Tagout (LOTO) Devices - LOTO devices are crucial for ensuring that all mechanical and electrical equipment associated with the confined space is de-energized and remains inoperative while work is being performed. This prevents accidental start-up of machinery which could lead to injuries.
  • Safety and Warnings Signs - Workplace signs play a critical role in warning about the hazards, indicating the nature of the confined space, and providing instructions or prohibitions specific to the site.

Precautions and Safety Tips For Working In Confined Spaces

Working in confined spaces has a ton of risks. Therefore, it is important to take extra precaution to ensure worker safety. Adherence to safety tips and taking proactive measures can significantly reduce the risk of accidents and limit the hazards associated with confined spaces.

Start by implementing a permit-required system where a complete and authorized permit is needed to enter a confined working space. Put a buddy system in place where workers outside the confined space are always ready to assist a worker inside in case of emergencies. More than that, ensure to maintain constant communication with team members inside and outside the confined space. Plan for emergencies by developing and rehearsing emergency response procedures tailored to the specific confined space and potential hazards and providing regular training and refresher programs to update all team members on confined space safety protocols and equipment.



A permit required confined space will often have which of the following hazards?

A permit-required confined space often has one or more of the following hazards: toxic or flammable atmospheres, oxygen deficiency or enrichment, physical hazards such as engulfment, or configuration hazards that can asphyxiate an entrant.

Who must know the hazards of a confined space?

All personnel involved in confined space work must be aware of the hazards. This includes entrants, attendants, supervisors, and rescue team members. Additionally, anyone involved in assessing or monitoring the space should also be knowledgeable about the potential hazards.

What is the least preferred method to control confined space hazards?

The least preferred method to control confined space hazards is Personal Protective Equipment (PPE). PPE is considered the last line of defense and should only be relied upon when other methods such as elimination, substitution, engineering controls, and administrative controls are not feasible.

What type of hazards occur in the majority of confined space accidents?

Atmospheric hazards are the most common type involved in confined space accidents. These include toxic gas exposure, oxygen deficiency, and explosive or flammable atmospheres.

What are the three main atmospheric hazards associated with confined spaces?

The three main atmospheric hazards in confined spaces are (1)Toxic Atmospheres, where the presence of harmful levels of contaminants or poisonous gasses, (2) Flammable or Explosive Atmospheres, which are conditions where flammable gasses or vapors are present in sufficient quantities to produce explosive mixtures, and (3) Oxygen Deficiency or Enrichment, where the Levels of oxygen below 19.5% or above 23.5%, which can respectively cause asphyxiation or increase fire risk.

The material provided in this article is for general information purposes only. It is not intended to replace professional/legal advice or substitute government regulations, industry standards, or other requirements specific to any business/activity. While we made sure to provide accurate and reliable information, we make no representation that the details or sources are up-to-date, complete or remain available. Readers should consult with an industrial safety expert, qualified professional, or attorney for any specific concerns and questions.


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Author: Herbert Post

Born in the Philadelphia area and raised in Houston by a family who was predominately employed in heavy manufacturing. Herb took a liking to factory processes and later safety compliance where he has spent the last 13 years facilitating best practices and teaching updated regulations. He is married with two children and a St Bernard named Jose. Herb is a self-described compliance geek. When he isn’t studying safety reports and regulatory interpretations he enjoys racquetball and watching his favorite football team, the Dallas Cowboys.