As defined by the Occupational Safety and Health Administration (OSHA), confined spaces are defined as areas that are large enough for workers to enter but have limited means of entry or exit and are not designed for continuous occupancy. Areas like these are common in businesses spanning several industries, and though they may appear relatively harmless at first glance, the conditions inside prove otherwise.
Confined space hazards can take many forms, which means that understanding and recognizing them with confined space training and taking steps to implement controls for them can represent the difference between life and death. Following permit-required entry procedures and training your team on the latest best practices is also critical.
At Alpha-Omega Training and Compliance (AOTC), we believe in empowering teams through proactive hazard identification and compliance support. The following guide will answer common questions, such as “What are the hazards of confined space?” It will also outline several conditions to answer, “Which of the following is considered a confined space hazard?”
Table of Contents
What Are the Hazards of Confined Space?
When entering or working in a confined space, your team members may encounter a range of hazards, some of which may be hidden or emerge unpredictably. These include the following:
- An oxygen-deficient (or rich) environment
- A flammable atmosphere
- Toxic gases or vapors (i.e., carbon monoxide, hydrogen sulfide)
- Engulfment (i.e., by grain, sludge, or sand)
- Live electrical components
- Mechanical or moving parts
- Limited visibility and restricted movement
Due to the enclosed nature of these areas, workers are often unable to vacate them if a hazard becomes evident quickly.
According to the Bureau of Labor Statistics, 1,030 workers suffered fatal injuries in confined spaces from 2011 to 2018. Leading causes of confined space fatalities include falls, engulfment, collapsed trenches, and the inhalation of harmful substances.
Hazards Specific to a Confined Space Can Be Categorized By…
Understanding and classifying the hazards your team faces is the first step to effective control and prevention. The categories that the dangers specific to a confined space can be attributed to are as follows:
Atmospheric Hazards
These include oxygen-deficient atmospheres or the presence of toxic vapors, and a lack of proper ventilation often worsens their effects. Oxygen deficiency is common in sewer systems, tanks, or vats; flammable vapors are usually found in oil refineries or spray paint booths, and toxic gases are a common concern in wastewater treatment plants.
Physical Hazards
These risks involve the structural or mechanical conditions within a confined space, such as:
- Moving Machinery: Rotating blades inside grain mills or mixers in food production facilities
- Entrapment Risks: Sloped walls or tapered bottoms in hoppers can trap workers
- Falling Objects or Slips: Overhead structures or slick surfaces can create injury risks
In particular, slips that result in a fall to a lower level represent one of the most common causes of confined space hazard fatalities; according to the Bureau of Labor Statistics research, 156 fatal incidents were caused by a fall to a lower level.
Chemical Hazards
Exposure to dangerous materials (such as residual solvents and acidic or caustic substances) often occurs in chemical processing and industrial cleaning tasks. Specifically, it is common in tank cleaning operations and paper mills, among other sectors that use similarly hazardous compounds.
Biological Hazards
Agriculture, wastewater, and food processing workers frequently encounter biological hazards. Mold and bacteria, for instance, can be found in old storage tanks or composting operations, while animal waste is a significant concern in livestock enclosures and manure pits.
The Three Main Atmospheric Hazards Associated With Confined Spaces Are…
OSHA requires atmospheric testing to be performed before an employee enters a permit-required confined space. The goal of these assessments is to check for atmospheric conditions that could endanger your employees, namely:
1. Oxygen Deficiency/Enrichment
According to OSHA, an atmosphere is considered oxygen-deficient if it contains less than 19.5% oxygen. Conversely, any atmosphere with more than 22% oxygen is considered enriched.
Deficient environments can form due to rusting metal, which consumes oxygen, while oxygen-rich spaces may be caused by leaking oxygen lines in or under medical facilities or labs. Either set of conditions, though, can be life-threatening.
2. Toxic Contaminants
Atmospheric testing also checks for contaminants that may endanger workers, primarily hydrogen sulfide and carbon monoxide. The former may be present in sewers and can be fatal at low concentrations. The latter is typically generated from internal combustion engines near confined spaces like tunnels and can quickly accumulate to deadly levels.
3. Flammable Gases or Vapors
OSHA also requires testing confined spaces for flammable gases or vapors, such as methane and petroleum. Methane is commonly found in landfills, sewers, and natural gas pipelines, while petroleum vapors may linger in fuel storage tanks long after they are emptied.
According to OSHA regulations, an atmosphere must contain less than 10% of the lower explosive limit (LEL) to permit safe entry.
Permit Required Confined Space Work Is Potentially Hazardous
OSHA designates a space as “permit-required” when it contains one or more of the following:
- A hazardous atmosphere
- Material(s) that could engulf a worker
- A configuration that could entrap or asphyxiate a worker
- Any other recognized threat to a worker’s safety or health
To that end, some examples of permit-required spaces include the following:
- Grain silos
- Maintenance holes
- Boilers or tanks
Permit-required confined space work is potentially hazardous to your employees and any rescue crews that have to respond in the event of an accident. As such, you must follow strict procedures when conducting such tasks, including the following:
- Written entry permits documenting conditions, authorized personnel, and protective measures that must be on hand
- An attendant needs to be on-site to monitor the entrant and communicate hazards to them
- A rescue plan with trained responders ready and available needs to be in place
Failing to follow permit-required mandates increases the risk of serious or potentially life-threatening injuries. Additionally, your organization could include fines and other penalties.
Common Engineering Controls Against Confined Space Hazards Include…
Both permanent and portable systems are available that are designed to prevent exposure and enable safe operations, such as:
- Mechanical Ventilation: Replaces hazardous atmospheres with fresh air (may include axial fans or air movers)
- Barriers: Placed around ledges or open access points to prevent accidental entry or falls
- Lockout/Tagout (LOTO) Systems: Prevents machinery from being accidentally started by locking controls and tagging access points with warning tags
- Gas Detection Systems: Check for flammables, oxygen, and toxic gases
- Retrieval Systems: Tripods, winches, and full-body harnesses enable non-entry rescue
You must have (and implement) the appropriate engineering controls based on your specific space and task.
Which of the Following Is Considered a Confined Space Hazard?
Consider these examples of workplace risks:
- Unguarded machinery, like a rotating auger inside a grain bin
- Engulfment materials such as loose flour in a food production silo
- Hazardous atmospheres that contain solvent vapors
- Live electrical components
As you might expect, the answer to the leading question is “all of the above.” If you know (or suspect) that any of these hazards threaten you and your workers, follow your confined space entry program and ensure that all involved parties are aware before proceeding.
Safety Best Practices for Confined Space Entry
A comprehensive confined space entry program is key to keeping your employees safe. Your program should incorporate established best practices, such as the following:
- Pre-Entry Hazard Assessment: Review the space’s history and perform appropriate testing
- Continuous Atmospheric Monitoring: Use real-time gas detectors before and during entry
- Effective Communication: Maintain radio or line-of-sight contact between the entrant and the attendant
- Proper PPE: Equip entrants with helmets, chemical gloves, flame-resistant clothing, and respirators as needed
- Entry Supervisor Oversight: Make sure that the attendant responsible for verifying safe conditions and signing the entry permit is adequately trained
Of course, these do not represent a rigid list; you can (and should) add other best practices based on your industry and the type of confined space hazards you encounter. Never cut corners when it comes to confined space safety.
The Importance of Training and Certification for Confined Space Work
OSHA requires specific confined space training for those involved in this type of work. Authorized entrants must be familiar with every kind of hazard, communication protocols, the proper use of PPE, and emergency procedures. Attendants must remain outside the space and monitor conditions, and entry supervisors must validate the space’s conditions, authorize permits, and cancel entries when they are deemed unsafe.
Your training program should include the following:
- Hands-on drills with the retrieval system
- Gas detector use
- Scenario-based exercises simulating real-world hazards
Properly documenting training is also critical, as is ensuring you provide your team with refresher training opportunities throughout the year.
Emergency Response Planning for Confined Spaces
Every confined space entry must include an emergency response plan with a non-entry and entry rescue component. Non-entry rescues are preferred; they involve a tripod, winch, or harness and are ideal for vertical entries like tanks and vaults.
Entry rescues require trained and adequately equipped personnel to enter the space. These methods are used when vertical retrieval lines are impractical or would create additional hazards.
When creating or revising your response plan, make sure that you do the following:
- Pre-identify the rescue team and practice regularly
- Ensure communication devices are operational
- Keep rescue gear on-site and ready at all times
OSHA requires that rescue personnel be available without delay; even minor pauses in response can increase the risk to workers and rescuers alike.
Partner With AOTC for Confined Space Training and Compliance Support
At AOTC, we specialize in designing confined space training that helps organizations like yours meet OSHA requirements and build a culture of prevention. These include the following:
- Confined space entry training and certification
- On-site hazard assessments
- Custom program development and mock drills
- Expert consulting for OSHA compliance
Contact and partner with AOTC today to protect your team and ensure that every confined space entry is conducted safely.
Frequently Asked Questions
What Are the 4 Types of Confined Space Hazards?
Confined space hazards fall into these four primary categories, each with distinct risks:
- Atmospheric hazards
- Physical hazards
- Chemical hazards
- Biological hazards
Each type of hazard requires specific identification, control, and mitigation measures.
What Are the Hazards of a Confined Space?
There are numerous hazards associated with working in confined spaces, such as:
- Oxygen deficiency
- Toxic or flammable atmosphere
- Engulfment
- Restricted movement
- Mechanical hazards
- Lack of visibility
Even experienced workers can be caught off guard, so proper training and preparedness are crucial.
What Are the 7 Key Hazards When Entering Enclosed Space?
When entering enclosed or confined spaces, workers face these seven primary hazards:
- Oxygen deficiency
- Toxic gases or vapors
- Flammable gases or vapors
- Physical entrapment
- Engulfment
- Mechanical hazards
- Lack of communication
Mitigating these hazards requires atmospheric testing and a dedicated attendant. You must also facilitate real-time communications and a rescue plan tailored to the space.
What Are 10 Examples of Confined Spaces?
Here are ten common examples of confined spaces found across various industries:
- Tanks
- Silos
- Sewers
- Tunnels
- Manholes
- Pipelines
- Ductwork
- Vats
- Crawl spaces
- Storage bins
All these spaces have limited access and egress. They may also contain serious atmospheric or physical hazards.