Confined Space: A Guide to Industrial Work in Enclosed Areas

A confined space is an area that is large enough for a human to enter, but with limited means of entering or exiting the area. These spaces are not intended for continuous human occupation. All three of these conditions are what define a confined space.

There are also permit-required confined spaces (PRCS). The Occupational Safety and Health Administration (OSHA) defines a PRCS as follows:

  1. Contains or has a potential to contain a hazardous atmosphere.
  2. Contains a material that has the potential for engulfing an entrant.
  3. Has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes downward and tapers to a smaller cross-section.
  4.  Or contains any other recognized serious safety or health hazard.

With stricter regulations and ageing assets, nearly all industries require inspections in confined spaces. Some examples of confined spaces include tanks, silos, pipes, sewer systems, chimney stacks, tunnels, maintenance holes, and more.

This guide contains a lot of information about confined space work and inspections—here is a menu you can use to jump around:

The Dangers of Confined Space Work

Confined space work is incredibly dangerous. Any emergency situation or rescue scenario is typically classified as a deficient program, so it is in the best interest of the Entry Supervisor to develop a successful plan.

The four main dangers of confined space entry are as follows:

  1. Mechanical hazards, like structural hazards, falling debris, collapse, moving parts of equipment, entanglement, engulfment, slips, or falls
  2. Risk of explosion or fire
  3. Inadequate oxygen for the worker to breathe without support, or the presences of asphyxiants
  4. Presence of hazardous biological or chemical substances

If a space has hazards present, then hazards must be mitigated before a person can enter. If confined space hazards cannot be mitigated, then a person must not enter until there are safety procedures in place, like proper equipment, rescue personnel present, and enough oxygen.

Fatalities often occur because a space is oxygen deficient, combustible, or toxic. It is imperative that these spaces are classified as PRCS and should be tested before to ensure safe entry as well as during the confined space work.


Confined Space Entry: How Confined Space Work Is Done

Before we go into confined space entry procedure, it’s important to note that OSHA requires anyone who plans to enter or work around a confined space to be certified under the OSHA Confined Spaces standard 29 CFR 1910.146. 

Because of the intricacies of confined space entry, special training is required in order to be certified. The confined space training is designed to help workers identify hazards and maximize safety protocol. 

Confined space entry training consists of learning how to:

  • Test the air quality for breathable air
  • Lock and tag out connecting piping
  • Force ventilation
  • Observe workers in the space
  • Develop a premeditated rescue plan

A worker who plans to enter or work around a confined space is required to pass an exam. A passing grade is considered to be 80% or higher, with a maximum of three attempts. A certified confined space worker will be able to:

  • Determine what is a “confined space” by definition and if it is a PRCS
  • Understand the application and scope of OSHA’s confined space entry standards
  • Understand OSHA’s requirements for safely developing and running a PRCS entry program
  • Identify when to use OSHA’s alternate entry and reclassification procedures
  • Know the responsibilities of entrants, attendants, entry supervisors, and contractors
  • Understand the requirements for emergency services and rescue
  • Have basic knowledge of general use and limitation of related equipment

Confined space entry procedures begin by determining if the space is a PRCS. If so, a permit will need to be obtained before moving forward. Then, workers will assess hazards, and develop an entry plan, and have a rescue plan. 

See the PRCS Decision Flow Chart for a full picture of confined space entry procedures:


What Kind of Work Is Done in Confined Spaces?

Confined space work consists of visual inspection or non-destructive testing (NDT) and mechanical work. 

Visual inspections and NDT ensure that infrastructure is properly maintained and maintenanced in order to avoid crumbling infrastructure and catastrophic accidents. NDT methods are most typically used in industrial applications, particularly for boilers and pressure vessels which could be incredibly dangerous if not properly maintained. 

Here are NDT methods that can be used in confined spaces:


Confined space industries

OSHA distinguishes three main industries that have confined space work: general industry, maritime, and construction.

General industry includes Oil & Gas, Chemical, Mining, Power Generation and Utilities, and Renewable Energy. Underground coal mines are incredibly dangerous PRCS that are highly toxic (miners have to pump in fresh air to combat unpredictable methane gas) and pose many risks like explosion, fire, and cave-ins.

Maritime includes shipping yards and marine vessels. Ballast tanks, which control the balance of ships by pumping sea water in and out, are confined spaces deep within a ships’ core. Because of the salinity of the sea water, corrosion is the main problem. Inspectors must inspect these tanks regularly for the health and longevity of the ship.

Construction includes residential and commercial properties. Sewer systems are a great example of necessary confined space entry. Typically a PRCS due to hazardous biological and chemical substances that are present, workers must gain entry to perform inspections for mechanical integrity and mechanical work like caulking.

Confined space regulations

Since confined space entry is incredibly dangerous, OSHA’s confined space regulations are detailed.

For a complete list of confined space regulations and requirements, visit OSHA’s Permit Required Confined Spaces standard.

Tools for Confined Space Work

On recently commissioned assets, a lot of work is being done on designs to limit the need for entry into confined spaces, but in most cases, it cannot be avoided completely.

DIY or industrialized “camera-on-a-stick”, or cameras lowered from the top of the confined space with wires can sometimes represent a very cost-efficient and effective solution to get images without human entry. These approaches are however limited to a small number of simple geometries as they cannot be operated beyond the spaces accessible with a 1-dimensional movement from the access point.


Searchcam's Recon - Camera designed for search and rescu

“Crawler” robots are the tool of choice for the inspection of long spaces with a consistent geometry such as pipes and ducts. Usually connected to the outside world  by a tether providing power and a data link, they allow to perform live inspection several hundred meters down a pipe for an unlimited time. However, they are mostly applicable in situations where there are no significant obstacles, T-junctions, or large change in the diameter of the pipe such as reservoirs.


Pipe inspection crawler from Inuktun

Other notable developments include “snake” robots, that are able to enter through a manhole and be operated inside a tank to maneuver around the internals and access virtually any place located close enough from the entry manhole; the drawback of such systems being its large weight and footprint. Those systems are currently mostly at the prototype stage and we are not aware of scaled-up deployments.


"Snake" robot from the Petrobot research project

Finally, other bespoke robotics systems such as “climber” robots use magnets to climb vertical surfaces and thus freely navigate the surface of metallic confined spaces, provided that the environment does not feature sharp angles that might block the movement. While some miniature versions of such climbers have been developed, most “climber” robots are typically heavy and expensive equipment.  

How Drones Can Help with Work in Confined Spaces

Using drone, or Unmanned Aerial Vehicles (UAVs) for indoor use, moreover in a confined and complex space could sound like a stretch, as most well-known use cases for drones feature wide open spaces that require coverage of large areas such as fields for agriculture or power line inspection.

However, UAVs have a serious advantage over other mobile robotics: their versatility. Their mobility in three dimensions allows to access virtually any place, from any angle, regardless of the shape, material and geometry of the environment.


This versatility also enables users to perform multiple tasks with the same device inside the plant, strongly shortening the time to return on investment. In addition, as those versatile tools can be often manufactured in larger volumes than bespoke machines, UAVs tend to be cheaper than custom ground robots.

However the use of drones indoors require one major problem to be solved: the risk of collisions. Indeed, in-flight collisions is the nightmare of any UAV pilot as a single contact can result in a crash and send the UAV to the ground. Even the best of the pilots cannot reliably avoid contacts with obstacles in complex confined spaces, moreover when flying beyond visual line of sight. Multiple other challenges await drones flying indoors: turbulences due to the small air volume or to drafts inside the confined space, presence of dust, signal transmission beyond line of sight, complete darkness and presence of reflective surfaces reducing image quality.

At Flyability, we tackled this issue through observing how insects solve this challenge: by using obstacles instead of avoiding them in order to navigate efficiently indoors. Think of a housefly finding its way out through an open window. Through specific flight algorithms and a mechanical design including a carbon-fiber decoupling system between the outer cage and the UAV itself, our Elios UAV can tolerate any collision in flight without perturbation. Moreover, on this drone designed for confined spaces inspection, the lighting and transmission system were designed to adapt to this particular environment.

This unique capability has won the trust of over 300 companies worldwide, which are using Elios to perform indoor visual and thermal inspection in confined spaces instead of sending workers in environments such as boilers, sewers, stacks or tanks.

An important limitation persist with the use of drones: the weight they can carry is limited by their size, and only small devices (for instance, Elios is only 40cm in diameter) can be conveniently used in small confined spaces. This means that they are unable to carry heavy sensors, but are perfectly capable of embedding cameras and thermal imagers.

What Does the Future Hold?

By lowering the costs and risks associated to confined space inspection through robotic solutions, it is to be expected that these inspections will be performed more often, in order to further reduce the risk of an emergency shutdown or accident. We forecast that no human will have to enter confined spaces for inspection by 2025.


Gathering more comfortably and more frequently data will allow for predictive maintenance and to a greater digitalization of the assets.

Drones will go in the direction of automated machines able to gather data without the intervention of any pilot. The data gathered will be organized on 3d models and analyzed to automatically identify defects and bring the attention of the asset operator immediately.

While the social and economic challenges arising from an increasing presence of robotics are numerous, their ability to go instead of us humans in dangerous, dull and dirty environments is definitely something we are looking forward to!

Download The Ultimate Guide to Commercial Drones In the Industrial Space


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