Confined Space Hazards and Safety Control Measures

Key Takeaways

• A confined space entry permit is essential to authorize safe entry, ensuring all safety protocols are in place before workers access a particular confined space.
• Conducting initial and periodic tests of the confined space environment is crucial for detecting hazards and maintaining safety during operations.
• Completing a confined space course and entry training equips workers with the necessary skills and knowledge to safely navigate confined spaces.
• The OSHA permit required confined space standard requires employers to implement safety measures, including the preparation of rescue and emergency services, for all confined space operations.

 

What Makes a Confined Space?

According to the Occupational Safety and Health Administration (OSHA) standards, a confined space has three defining characteristics:

1. It’s large enough for an employee to enter and perform tasks.
2. It has limited or restricted means of entry or exit.
3. It’s not designed for continuous occupancy.

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, and sewers. 

These environments share an enclosed nature that makes them inherently hazardous, primarily because of limited ventilation and tricky egress. When you combine these features with potential hazards like toxic atmospheres or oxygen deficiency, confined spaces demand heightened awareness, preparation, and compliance.

 

What Must Happen Before Any Work May Be Performed in a Confined Space?

Before any worker steps into a confined space, a structured and detailed process must take place to ensure their safety. These steps, when properly executed, minimize the risk of accidents and fatalities associated with confined space hazards. Let’s break it down into clear, actionable elements:

1. Conduct a Comprehensive Confined Space Risk Assessment: Evaluate all potential hazards, including atmospheric conditions, engulfment risks, and environmental factors. Document findings and share them with all personnel to ensure hazard awareness. Additionally, do not forget to assess your facility's training needs, including Confined Space Supervisor.
2. Obtain a Confined Space Permit: A permit formalizes authorization to enter the space, listing hazards, safety measures, and authorized personnel, monitoring results and permit limitations. It ensures all precautions are reviewed and approved before work begins. From my experience, it’s also super important to understand the nature of work inside the space to help with ventilation plans; this will ensure enough air changes during the entry.
3. Test and Monitor the Atmosphere: Use calibrated equipment to test for oxygen levels, toxic gases, and explosive atmospheres. Continuous monitoring is essential as conditions can change unexpectedly.
4. Establish Isolation Procedures: Separate the confined space from external hazards by locking out equipment, blocking pipelines, disconnecting piping or other sources, and disabling energy sources. This prevents unintentional activation or entry of hazardous materials.
5. Develop and Communicate a Rescue Plan: Create an emergency plan with assigned roles, rescue equipment, and trained personnel. Regular rehearsals ensure quick and effective responses in case of an incident.
6. Ensure Proper Training and Competence: Provide tailored training to entrants, attendants, and supervisors on hazards, equipment use, and emergency protocols. Trained workers are better equipped to recognize risks and act appropriately.
7. Verify the Work Area is Safe: Inspect the space to confirm it is free of dangerous residues and properly ventilated. Ensure all required safety equipment is in place and functioning before entry.

A comprehensive pre-entry process significantly minimizes risks associated with confined spaces. Neglecting even a single precaution can lead to severe and potentially life-threatening consequences.

 

10 Major Confined Space Hazards

Hazards specific to a confined space can be categorized primarily into three main groups: atmospheric hazards, physical hazards, and biological hazards. These hazards often overlap or amplify each other, creating complex risk profiles that demand specific control measures. Below is a detailed breakdown of the ten most common hazards encountered in confined spaces:

Atmospheric Hazards

The most dangerous threat in confined spaces often comes from the air itself. Atmospheric hazards include toxic atmospheres from gases like hydrogen sulfide, oxygen deficiency caused by chemical reactions or rusting, and oxygen enrichment, which increases the risk of fire. Workers may also encounter flammable or explosive atmospheres if gases like methane or vapors from chemicals accumulate. When using generators, welding machines, or portable air compressors, it’s important to recognize that carbon monoxide can pose a significant hazard.

Electrical Hazards

Confined spaces such as electrical vaults, manholes, substations, and maintenance pits often house electrical systems, making them high-risk areas for electrical shock or electrocution risks. Energized equipment, exposed wiring, or the use of ungrounded tools in damp conditions significantly increase these dangers. The use of lockout/tagout (LOTO) devices is critical to isolate electrical sources that can lead to fatal incidents. These devices are applied to disconnect electrical systems, ensuring no accidental re-energization occurs during maintenance or repair.

Chemical Exposures

Chemical hazards arise from the presence of flammable or toxic substances, residues, or vapors. Workers may come into contact with 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. Even small chemical spills can produce harmful vapors in an enclosed space.

Access Restrictions

The limited entry and exit points of confined spaces create serious challenges during emergencies. Narrow openings can trap workers, hinder rescue efforts, or prevent equipment from being brought into the space. These restrictions also complicate evacuation when conditions deteriorate.

Fire Hazards

Flammable substances, oxygen-enriched atmosphere, and heat sources create an ever-present fire risk in confined spaces. Ignition of these materials can occur from static electricity, sparks from equipment, or hot surfaces, leading to severe injuries or fatalities. Poor ventilation exacerbates this danger by allowing flammable vapors to accumulate.

Flood Hazards

Unexpected water or liquid entry can transform a confined space into a death trap. Spaces such as tunnels, tanks, or sewers are particularly vulnerable to flooding from internal sources like pipe bursts or external sources like heavy rainfall. Workers risk drowning or being trapped if flooding occurs, hypothermia, and exposure to water-borne contaminants, along with potential damage to equipment.

Excess Oxygen

High levels of oxygen in a confined space can be as dangerous as low levels. Oxygen enrichment can occur due to faulty equipment or leaks from oxygen tanks, significantly increasing the likelihood of materials that are normally non-flammable igniting easily and burning intensely. Even minor sparks can ignite fires in these conditions.

Explosions

Confined spaces can quickly become explosive environments due to combustible materials, gas buildup, or the presence of flammable substances. Spaces with poor ventilation allow these materials to accumulate, and a single ignition source, such as a spark or friction, can result in catastrophic explosions. Explosions can cause severe injury or death and significant structural damage, complicating rescue and recovery efforts.

Temperature Extremes

Extreme temperatures, either high or low, are a common hazard in confined spaces, influenced by external conditions or internal operations. Excessive heat can lead to heat stress, dehydration, or heatstroke, especially in spaces with poor ventilation. Cold environments, on the other hand, increase the risk of hypothermia or frostbite, particularly when workers are stationary for extended periods. 

During the summer months, employers should provide proper ventilation and designate shaded or climate-controlled areas to help workers stay comfortable. Wearing chemical-resistant or heavy protective PPE in high temperatures increases the risk of heat stress and must be carefully managed to prevent related hazards. Entry conditions should prioritize both safety and worker comfort to promote efficient and uninterrupted project execution. 

Dust

Accumulation of combustible dust in confined spaces is a significant health hazard, particularly in industries dealing with grains, flour, or certain metals. Dust suspended in the air can explode if ignited, especially in poorly ventilated spaces. Even non-combustible dust can impair visibility and harm respiratory health.

 

What Is an Example of an Engulfment Hazard in a Confined Space?

Grain storage bins are a common confined space where engulfment hazards frequently occur. Grains behave like a fluid, and even standing on its surface can cause a worker to sink. If the grain is being unloaded or shifted, it creates a funnel effect that pulls the worker downward, often burying them completely in seconds.

In February 2023, a 43-year-old employee at Westfield, Illinois, became trapped in a grain bin for five hours while attempting to unclog soybeans piled up to 30 feet high inside the bin. The worker was rescued with minor injuries, but an OSHA investigation revealed multiple violations of grain-handling safety standards, including failing to de-energize equipment and provide safety gear.

Trenches used in construction or utility work are another setting for engulfment hazards. Workers entering a trench are at risk of soil or sand collapsing from the inwardly converging walls, particularly when the trench is not properly supported or shored. Loose or unstable soil can suddenly give way, burying workers and trapping them under heavy material. Remember that soil sloping, shoring, trench boxes, and the potential for water or other liquids to seep into the space are extremely important factors to consider.

 

What Type of Material Presents an Engulfment Hazard?

Materials that present engulfment hazards are typically loose, free-flowing solid substances such as grain, sand, soil, or liquids. These materials often pile unpredictably, creating unstable surfaces that collapse under weight, leading to suffocation or crushing injuries. The unpredictability of how these materials flow, especially when disturbed, significantly increases the danger in confined spaces.

 

Who Must Know the Hazards of a Confined Space?

Understanding confined space hazards requires collaboration across multiple roles, not just the workers entering the space. The following are key roles that must have a thorough understanding of the hazards associated with confined spaces:

• • Authorized Entrants: Perform work inside the confined space and must have detailed knowledge of specific risks and hazards.
  • Attendants: Monitor conditions from outside, maintain communication, and respond promptly to emergencies.
  • Entry Supervisors: Ensure all safety protocols are followed and verify that the confined space is safe for entry.
  • Confined Spaces Advisors: Provide specialized expertise by creating safety plans, conducting risk assessments, and auditing compliance with regulations.
  • Rescue Teams: Must understand confined space hazards to carry out effective and safe emergency rescues.

All of these positions play a crucial role in delivering a safe and comfortable space for the entrants.

 

General Confined Space Safety Solutions

Below are the critical elements of safety protocols necessary for confined space operations.

1. Access and Egress: Confined space entryways should be clear, easily accessible, and properly marked similar to the image above. Emergency plans should include ladders, platforms, or harnesses that can assist in the efficient evacuation of workers if needed.
2. Competence, Training, Supervision, and Suitability: Workers and supervisors must undergo comprehensive training covering hazard recognition, equipment use, and emergency procedures. Supervisors ensure adherence to safety protocols, and workers' physical and psychological fitness must be evaluated for confined space tasks.
3. Permit-to-Work Procedure: A formal written system used to specify the work, hazards, safety checks, and authorized personnel involved. Permits are time-bound and reviewed after task completion to capture lessons for future safety enhancements.
4. Communications: Reliable two-way communication devices and pre-determined emergency plans are essential for maintaining constant contact between workers inside the confined space and the team outside.
5. Gas Purging and Ventilation: These systems remove harmful gases and replace them with fresh air to prevent the build-up of dangerous air contaminants that pose risks of asphyxiation, fire, or explosion.
6. Dangerous Residues: 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. 
7. 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.
8. Mechanical, Electrical, and Process Isolation: This 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.
9. 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.
10. Other Personal Protective Equipment (PPE): While respiratory system 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. Some spaces may also require workers to donn personal O2 detectors as another layer of protection to ensure oxygen levels are acceptable and safe. 
11. Safe Use of Work Equipment: 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 the manufacturer's guidelines to ensure they remain in safe working condition.

 

Confined Space Control Measures

To control confined space hazards, integrate the following measures into your safety plan: 

Confined Space Training

Proper confined space training significantly reduces the risk of accidents and fatalities. Workers who understand the hazards and are equipped with the right skills are better prepared to avoid mistakes and respond appropriately to emergencies. Considering this, here are the key topics and elements that should be included in a comprehensive confined space training program:

• • Hazard Identification: Workers are trained to recognize hazards in confined spaces, such as toxic gases, low oxygen, and mechanical risks, using tools like gas detectors and assessing potential dangers.q
  • Use of PPE: Training ensures workers know how to select, use, inspect, and maintain PPE like respirators, protective suits, and harnesses to protect against specific confined space hazards.
  • Safe Entry and Exit Procedures: Workers learn how to safely enter and exit confined spaces using proper access equipment like ladders and harnesses, and secure entry points to prevent unauthorized access.
  • Emergency Response and Rescue Procedures: Training covers how to react during emergencies, use rescue equipment, and assist in rescues without causing further harm.
  • Atmospheric Testing and Monitoring: Workers are trained to use gas detectors to test for oxygen levels, flammable gases, and toxic substances, with continuous monitoring when necessary.
  • Lockout Tagout Procedures: Training covers isolating hazardous energy sources by properly locking and tagging out mechanical, electrical, and chemical systems to prevent accidental activation.
  • Communication Protocols: Workers are trained to use radios or signals to maintain communication with team members and supervisors, especially during emergencies.
  • Roles and Responsibilities: Training clarifies the duties of all personnel involved in confined space work, including entrants, attendants, and supervisors, ensuring coordinated safety measures.
  • Refresher Training: Periodic refresher training is essential to keep workers updated on confined space safety procedures, regulations, and equipment advancements.

Confined Space Hazard Assessment

Hazard assessment is a confined space pre-entry step aimed at determining potential risks and dangers that can result in serious injury or death if not properly identified and mitigated. Here is an overview of the necessary steps taken in identifying confined space hazards:

• • Oxygen-Deficient Atmospheres: Identified using an oxygen meter to test the atmosphere for oxygen levels before entry, with continuous monitoring if levels are unstable.
  • Flammable or Explosive Atmospheres: Detected by using a gas detector to check for flammable gases, Lower Explosive Limits, like methane, propane, VOCs, or other explosive or flammable vapors before entry into the confined space.
  • Toxic Atmospheres: Identified through gas detectors that monitor for toxic gases such as hydrogen sulfide or carbon monoxide, both before and during the operation.
  • Mechanical and Physical Hazards: Assessed by inspecting the space for entrapment, crush points, moving machinery, and unstable structures, along with applying lockout/tagout procedures to prevent accidental activation.

Confined Space Isolation

Confined space isolation involves controlling hazardous energy sources through several procedures. The goal of isolation is to eliminate the risk of accidental exposure to harmful substances, unexpected mechanical movements, or the activation of hazardous energy sources while work is being performed. Lockout tagout ensures that all identified energy sources, such as electrical circuits or hydraulic systems, are de-energized, locked, tagged, and verified before work begins, with locks removed only by the worker who applied them. 

For pipelines or ducts, physical disconnection or blinding is often necessary to prevent hazardous materials from entering the space, while heat-producing equipment must be fully disconnected and cooled to avoid burn or fire risks. In industries like petrochemicals, a double block and bleed system is used to isolate pipelines, providing an extra safety measure by draining material between two closed valves, but sometimes may not be 100% effective.

From my experience, blinding or isolating the process away from the space is more effective as double block and bleed uses valves that may leak. Facilities must evaluate and determine the best, most effective isolation for their hazards and spaces. 

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. Remember also to ground air movers to prevent any static discharge.
  • 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. Attendants must also be clear of their role when it comes to rescue - they should not enter the space at any point in time. 
  • Lockout Tagout 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. Confined space covers also serve as physical barriers to protect unattended confined space openings from unauthorized access or accidental entry.
  • 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.

Ensuring safety during confined space entry requires adherence to strict protocols, including obtaining a confined space permit, conducting initial and periodic tests of the confined space environment, and completing a comprehensive confined space course. Each particular confined space presents unique hazards, making compliance with the OSHA confined space standard essential and critical.

My experience in ensuring entrant and confined space safety relies heavily on all team members being well trained, communicating and discussing hazards and protocols of entry before the space is entered and holding post-entry discussions to discuss what could go better. It all depends on everyone paying attention and ensuring the safety of the entrants and maintaining safe conditions inside and outside the space. 

 

FAQs

What are the three types of confined spaces?

The three types of confined spaces are non-permit confined spaces, permit-required confined spaces, and enclosed spaces with hazardous atmospheres or physical dangers.

What is the normal oxygen level in a confined space?

The normal oxygen level in a confined space is between 19.5% and 23.5%.

What PPE is required for confined space entry?

Required PPE for confined space entry may include respiratory protection, hard hats, protective suits, gloves, safety boots, and harnesses.

What is the maximum allowable temperature for confined space entry?

The maximum allowable temperature for confined space entry typically should not exceed 104°F (40°C), but this can vary depending on the task and regulatory guidelines.

What are the confined space training objectives?

The objectives of confined space training are to ensure workers understand hazard identification, safe entry and exit procedures, emergency protocols, and the proper use of PPE and rescue equipment.