A few weeks ago, a new coworker asked me if a narrow aisle stacked with pallets qualified as a confined space. It sparked a discussion about what truly defines one and why it matters. Misidentifying such spaces can lead to overlooked hazards and unnecessary risks. In this article, I’ll explore the common confined space examples, their defining characteristics, and the hazards that make them dangerous.
Key Takeaways
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Understanding confined spaces helps identify risks and apply the correct safety measures to protect workers from hazardous conditions.
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Manholes are classic confined spaces with limited entry, poor ventilation, and atmospheric hazards like toxic gases, making safety measures essential for entry.
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Lockout tagout prevents accidental equipment activation, isolating hazards during maintenance in confined spaces.
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Engulfment hazards escalate quickly, as materials like grain or water can trap workers, leaving little time for rescue.
Define Confined Space
According to the Occupational Safety and Health Administration (OSHA) standards outlined in Section 29 CFR 1910.146, a confined space is defined by three specific characteristics:
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It is large enough for someone to enter and perform work.
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It has limited or restricted means of entry or exit.
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It is not designed for continuous occupancy.
These characteristics make confined spaces inherently hazardous. Limited ventilation systems, restricted movement, and risks like toxic gases, engulfment, or entrapment make these spaces dangerous without proper precautions. But not every tight or enclosed area qualifies as a confined space, and that’s where things can get confusing.
Let’s go back to that moment when my coworker asked if a narrow aisle stacked with pallets was a confined space work. At first glance, it might seem like one. The area was enclosed on both sides by tall stacks of pallets, creating a tight, tunnel-like feel. Movement was restricted, and it felt a bit claustrophobic.
But here’s why it wasn’t a confined space. First, the aisle is designed for humans to occupy, it wasn’t fully enclosed, allowing air circulation. Second, entering or exiting wasn’t restricted; you could walk out at either end without much effort. Finally, the space wasn’t inherently hazardous in its normal condition. There were no toxic gases, engulfment risks, or structural dangers present.
It was a tight space, yes, but it didn’t meet the formal criteria for a permit required confined space. This distinction matters to avoid unnecessary procedures or, worse, a failure to recognize actual confined spaces where hazards are present.
Examples of Confined Spaces
Confined spaces exist in various environments, from industrial sites to agricultural settings. Each example has unique characteristics, hazards, and entry requirements. Let’s break down some of the most common confined spaces to understand what makes them hazardous and how to approach them safely:
Tanks and Vessels
Tanks and vessels are enclosed containers used to store liquids, gases, or other materials. These permit required confined spaces are large enough for a person to enter for maintenance or cleaning, but they have limited access points, often through small hatches or openings. Poor ventilation in tanks can lead to the accumulation of hazardous gases or a lack of oxygen.
Additionally, the materials stored inside, such as chemicals or fuel, can present toxic or flammable risks. Entering a tank requires specific precautions, including air quality testing, respirators, and confined space permits to manage potential dangers.
Sewers
Sewers are underground chambers designed to transport wastewater. While their size accommodates workers who perform maintenance or repairs, sewers are confined due to their restricted entry points and hazardous conditions. These include toxic gases like methane or hydrogen sulfide, oxygen deficiency, and the risk of flooding or engulfment.
Sewers also present physical dangers, such as slippery surfaces and limited visibility. Worker safety procedures for sewer entry include ventilation equipment, gas detection devices, and personal protective equipment (PPE) to mitigate these risks.
Silos
Silos, whether used for silage or grain storage, are vertical storage units with small access points and limited airflow. They pose significant risks, including engulfment, as the stored material can shift and trap workers. Harmful gases, such as carbon dioxide from fermentation, may also accumulate.
The image above shows what it looks like inside an enclosed grain bin. A worker entering this space without proper training risks being engulfed by shifting grain in seconds. Entry into silos requires monitoring air quality, using personal harnesses or lifelines, and maintaining communication with a spotter outside the space.
Pits
Pits, such as maintenance or inspection pits, are openings in the ground used for various purposes, including vehicle repairs or equipment servicing. While open at the top, pits are confined spaces due to limited exit routes and the potential for hazardous gas buildup at lower levels.
Risks include slips, falls, and exposure to harmful fumes, especially if the pit is in a poorly ventilated area. Safe entry requires proper ventilation, barriers to prevent falls, and gas detection tools to monitor air quality.
Boilers
Boilers, used in industrial and commercial heating systems, are enclosed spaces with high temperatures and have limited space for entry points. Workers may need to enter boilers for maintenance or repairs, where they often encounter risks such as burns from residual heat, exposure to steam, and reduced oxygen levels within the confined space. Safe work in boilers often involves waiting for the equipment to cool, monitoring air quality, and using appropriate protective gear.
Tunnels and Pipelines
Tunnels and pipelines are long, narrow passageways that restrict movement and airflow. These spaces are common in construction sites and utility work, such as water or gas line installations. Hazards include oxygen deficiency, the risk of collapse, and entrapment. Entry procedures involve communication systems, ventilation systems, and emergency evacuation plans to address the unique challenges of these spaces.
Hoppers
Hoppers, used for handling bulk materials like sand or gravel, are tapered containers with restricted entry points. The sloped design makes engulfment a serious hazard, as materials can shift unexpectedly. Workers must use fall protection and avoid entering unless absolutely necessary, with proper equipment and communication systems in place.
I remember reading about a tragic confined space accident that happened in 2023. A miner entered a hopper to clear an obstruction, and while he was inside, a front-end loader unknowingly dumped two loads of crushed limestone into the hopper, burying him. This devastating incident highlighted critical failures in communication, hazard isolation, and confined space entry protocols.
When you think about it now, proper measures, such as lockout/tagout procedures, external obstruction-clearing methods, and effective communication, could have prevented this tragedy.
Water Supply Towers
Water supply towers, used for storing large volumes of water, are confined spaces due to their enclosed design, limited access points, and lack of ventilation, which can lead to oxygen deficiency or hazardous gas buildup. Accidents often occur during maintenance, cleaning, or repairs, where workers face drowning risks, chemical exposure, or falls from slippery or corroded surfaces while working at height. Safe entry in water supply towers demands thorough preparation, including safety harnesses, spotters, air quality monitoring, clear communication, as well as rescue plans and protocols to prevent accidents.
Shipping Containers
Shipping containers though seemingly straightforward, qualify as confined spaces during certain operations such as storage, repair, or repurposing. Their enclosed space design, with limited airflow through a single door, often results in poor ventilation.
This can lead to the accumulation of hazardous gases, oxygen depletion, or extreme temperatures, especially if the container has been sealed for long periods or exposed to the sun. Entering a shipping container without proper air quality testing, ventilation, or PPE can result in asphyxiation, chemical exposure, or even fire-related injuries.
Access Shafts
Elevator shafts are a specific type of access shaft commonly encountered in construction, building maintenance, or repair projects. These shafts are confined spaces due to their narrow, vertical design and restricted access points. Accidents in elevator shafts often occur due to inadequate fall protection, insufficient communication among workers, or failure to secure the machinery before entry.
For example, a worker entering an elevator shaft without isolating the system risks being struck by a descending elevator car or counterweight. To address these risks, strict safety protocols must be in place. Workers should use harnesses and fall arrest systems and isolate the elevator system using proper lockout tagout devices before entering the shaft.
“Dumb-waiters” are also similar to elevator shafts and the same precautions should be used. There are many stories where employees simply trying to get a dumb-waiter to function and have tragically lost their lives due to a lack of knowledge in hazard identification, LOTO, and confined space entry.
Is a Manhole a Confined Space?
Yes, a manhole is a classic example of a confined space. Manholes provide access to underground utilities, such as sewers or electrical systems. Its access is through a small vertical opening, which limits ventilation and makes rescue efforts challenging.
What makes manholes particularly hazardous is their enclosed nature and the potential for hazardous atmospheres to develop inside. Harmful gases like methane or hydrogen sulfide can accumulate due to decaying organic material or industrial waste. Oxygen levels can also drop, creating an asphyxiation risk.
What Is an Example of an Engulfment Hazard in a Confined Space?
One of the most common and well-documented examples of an engulfment hazard occurs in grain bins. Grain storage bins are used to store large quantities of grain, but the stored material behaves like a fluid when disturbed. For example, when a worker steps onto the surface of stored grain, it can shift or collapse, pulling the worker under like quicksand. Within seconds, the worker can become engulfed, unable to escape due to the weight and pressure of the surrounding grain.
Preventing engulfment hazards starts with a comprehensive understanding of the hazards present and strict adherence to safety protocols. If entry is required, the following measures can help reduce the risk:
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Material Flow Isolation: Before entry, all electrical equipment that could cause material movement, such as augers or flow mechanisms, should be deactivated and locked out.
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Safety Harnesses and Lifelines: Workers entering confined spaces with engulfment risks should wear properly secured harnesses connected to lifelines for easy retrieval in case of an emergency.
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Standby Personnel: A trained standby team should monitor the access points and be equipped to initiate a rescue if necessary.
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Testing and Monitoring: Air quality and material stability should be tested before entry to assess any immediate hazards.
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Communication Systems: Continuous communication between the workers inside the storage tank and those outside is critical to quickly address any problems.
Engulfment hazards are particularly perilous because they escalate rapidly, leaving little time for workers to react or for rescue teams to intervene. Once a person is engulfed, the pressure exerted by the surrounding material restricts movement and breathing and can ultimately cause serious injuries.
FAQs about the Examples of Confined Spaces
What is a NC2 confined space?
A NC2 confined space refers to a confined space with moderate risk levels that typically requires precautionary measures but does not involve highly hazardous conditions. These spaces may still pose risks like low oxygen levels or toxic gases but do not typically require advanced rescue procedures.
What is a NC3 confined space?
A NC3 confined space is classified as high-risk due to the presence of severe hazards, such as hazardous atmospheres, engulfment risks, or extreme difficulty for rescue. Entry into NC3 spaces requires detailed planning, advanced safety equipment, and highly trained personnel to manage the significant risks involved.
Is a cold room a confined space?
A cold room can be considered a confined space if it has limited openings and exit points and is not intended for continuous occupancy. Additionally, risks like low oxygen levels or being locked inside could elevate it to confined space status under certain conditions.
Can a roof be a confined space?
A roof is generally not a confined space unless it meets the criteria of limited entry and exit, is not designed for continuous occupancy, and presents specific hazards. For example, a roof area enclosed on all sides with poor ventilation could qualify as a confined space.
What is not an example of a confined space?
An open-air workspace, such as a large, unrestricted warehouse or a fenced yard, is not an example of a confined space because it lacks the characteristics of limited space for entry, poor ventilation, and hazardous conditions typically found in confined spaces. Spaces that allow unrestricted airflow and movement without inherent risks are excluded from this classification.