20 hazards in confined spaces and how drones reduce them
Work in confined spaces is very risky. In this article we look at 20 hazards that occur in confined spaces and show how drones such as the Flyability ELIOS 3 help to reduce the risks.
20 hazards when working in confined spaces
When it comes to work in confined spaces, safety and risk reduction come first. These areas are often hard to access, poorly ventilated and harbour unpredictable hazards. A thorough risk assessment is essential before people enter these environments. In the following 20 points we look at the most important hazards that can arise when working in confined spaces – including the possibility of reducing many of these risks by using drone technology such as the Flyability ELIOS 3.
Christian Engelke
1. Oxygen deficiency
The oxygen content of normal breathing air is around 20.9%. If the oxygen content in confined spaces falls, breathlessness, dizziness and ultimately asphyxiation can follow. Oxygen deficiency can arise when oxygen is displaced by gases such as nitrogen or carbon dioxide. Oxygen consumption by people or machines in enclosed spaces without adequate ventilation can also lead to life-threatening situations. The insidious thing is that oxygen deficiency is barely noticeable: those affected can lose consciousness without warning. With the drone, nobody has to enter the vessel; gas-free testing for personnel is not needed.
2. Oxygen enrichment
Too high a proportion of oxygen – above the natural level of 20.9% – can considerably increase the risk of ignition. Even a small spark is enough to cause a fire or explosion, because oxygen makes materials burn more readily. Such an excess can be caused by leaking oxygen cylinders or faulty welding equipment. Handling oxygen in confined spaces therefore calls for particular care. During a drone inspection, nobody is in the space. The drone itself can, however, be an ignition source; whether it may fly is decided by the operator as part of its release procedure.
3. Hazardous gases
Toxic gases that are difficult or impossible to perceive can accumulate in confined spaces. Particularly dangerous gases are:
- Hydrogen sulphide (H₂S): a highly toxic gas that smells of rotten eggs at low concentrations but can be odourless and fatal at higher concentrations. It often occurs when organic matter decomposes.
- Carbon monoxide (CO): a colourless, odourless gas produced by incomplete combustion. Carbon monoxide prevents oxygen transport in the blood and, depending on the concentration, can soon lead to unconsciousness and death.
- Methane (CH₄): an explosive gas often released in sewage treatment works or when organic material decomposes. Although it is non-toxic, it is highly flammable.
- Carbon dioxide (CO₂): in large quantities it can displace oxygen and lead to asphyxiation.
With the drone, nobody breathes in these gases: personnel stay outside, and gas-free testing for personnel is not needed.
4. Explosion hazard
Explosive gases and their mixtures with air are dangerous when their concentration lies within a certain range, known as the explosive range or flammable range. This range is defined by the lower explosive limit (LEL) and the upper explosive limit (UEL). Important explosive gases in confined spaces are listed below. Please refer to the safety data sheet or the GESTIS substance database for the explosive limits; we deliberately do not give individual values here.
- Methane (CH₄): produced when organic matter decomposes, for example in sewage treatment plants or mines.
- Hydrogen (H₂): in industrial processes and refineries; very wide flammable range.
- Propane (C₃H₈): fuel gas; heavier than air, collects in low-lying areas.
- Butane (C₄H₁₀): in gas cylinders; heavier than air, collects at floor level.
- Carbon monoxide (CO): produced by incomplete combustion; odourless and toxic.
- Ethane (C₂H₆): raw material in the chemical industry.
- Acetylene (C₂H₂): welding gas; very wide flammable range and unstable.
- Ammonia (NH₃): in the chemical industry and fertiliser production; also toxic and irritant.
Conditions for an explosion:
- Ignition source: An explosion can only occur if there is an ignition source. This can be a spark, an open flame, a hot object or even a static discharge.
- Explosive concentration: The gas must be present at a concentration between the LEL and the UEL. If the concentration is too low (below the LEL), the mixture is too lean, and if it is too high (above the UEL), it is too rich to explode.
- Heat: The hotter the environment, the more likely a gas is to ignite. Some gases can also ignite without an ignition source at high temperatures, a process known as auto-ignition.
- Pressure: Higher pressure generally widens the explosive range and increases the effect of an explosion. In confined spaces, gases can also accumulate more easily in dangerous concentrations.
- Ventilation: In poorly ventilated confined spaces, gases can accumulate unnoticed because they are not diluted or carried away. A lack of adequate air exchange increases the risk of an explosive atmosphere.
Examples of situations with an explosion hazard:
- Tank cleaning: Gases such as methane or hydrocarbons can accumulate in decommissioned tanks or silos. When work is carried out in these areas, sparks from tools or machinery can trigger an explosion.
- Sewage treatment plants: Methane and hydrogen sulphide are often produced when organic material decomposes. In poorly ventilated areas such as septic pits, there is a risk of explosion.
- Chemical storage: Ammonia or butane in storage tanks that are not properly ventilated can accumulate and become explosive, especially if there is no continuous monitoring.
With the drone, nobody is in the space during the inspection. Our drones are not explosion-protected; in hazardous (Ex) areas, the operator decides whether the drone may fly.
5. Risk of engulfment in bulk materials
Bulk materials such as grain, sand or chemicals can slip or slide down during work in silos and bury people. Once a person is buried under the material, there is an acute risk of suffocation, as the weight of the material makes any movement or escape impossible. With the drone, nobody has to enter the silo; the risk of personnel being buried is removed.
6. Mechanical hazards
Confined spaces often contain moving machinery or equipment that can cause serious injury if started incorrectly or unexpectedly. Rotating mixers, conveyor belts or ventilation systems, for example, can be a hazard if they are switched on accidentally while people are nearby. During a drone inspection, nobody is in the space if equipment starts up unexpectedly. It is still switched off and secured so that the drone is not damaged.
7. Falls from height
Many confined spaces, such as silos or shafts, require work at great height or depth. Inadequate fall protection – for example missing ladders, fall arrest systems or safety attendants – can lead to serious accidents. Even a small lapse in attention can be fatal if no protective system is in place. With the drone, nobody has to work at height or depth; scaffolding and fall protection for the inspection are not needed.
8. Electrical hazards
Confined spaces are often damp or conductive, which considerably increases the risk of electric shock. Inadequately insulated cables or improperly operated electrical equipment can cause fatal electrical accidents. It becomes particularly dangerous when residual current devices (RCDs) are missing or defective and do not trip in the event of a fault. The drone is controlled from outside; nobody works with electrical equipment in the damp space.
9. Lack of rescue options
In an emergency, rescue teams may find it difficult to get into confined spaces or to bring an injured person out. Narrow passages, blocked access points or hard-to-reach locations slow down rescue considerably, which can be life-threatening in critical situations. Where nobody goes in, nobody has to be rescued: during a drone inspection, personnel stay outside.
10. Chemical reactions
Different chemicals that are processed or stored in confined spaces can trigger dangerous reactions on contact with each other. Acids and bases, for example, can react strongly and exothermically, releasing toxic fumes or causing fires. It is particularly dangerous when these reactions take place in poorly ventilated spaces. During a drone inspection, personnel are outside if fumes are released.
11. Heat and cold
Confined spaces can be extremely hot or cold. Hot surfaces or chemical reactions can cause burns, while cold media can cause frostbite. A further danger is that heat or cold builds up in the confined space and cannot dissipate because of a lack of ventilation. With the drone, nobody in the space is exposed to heat or cold; vessels and boilers are out of service and released for the inspection.
12. Biological hazards
Biological hazards often occur in damp or poorly ventilated confined spaces. Bacteria such as Legionella can accumulate in water or damp environments and cause serious infections when inhaled. Moulds and other microorganisms are also a hazard and can cause respiratory illnesses. With the drone, nobody in the space breathes in germs or mould spores.
13. Restricted access openings
Many vessels, tanks and shafts can only be accessed through small manholes or entry hatches. Getting in and out with respiratory protection, a safety harness and tools is therefore laborious and time-consuming. Narrow openings also hinder ventilation and make it considerably harder to rescue an injured or unconscious person, who often can only be recovered with a rescue hoist and several helpers. Access, the rescue route and rescue equipment must therefore be planned before work begins. A drone, by contrast, fits through the manhole without anyone having to enter.
14. Inadequate lighting
Many confined spaces lack sufficient light, which makes working there dangerous. Hazards go unnoticed, and missteps or collisions can lead to serious injuries. Poor visibility can also mean that important work steps are overlooked. The drone carries its own lighting, and personnel stay outside.
15. Psychological strain
The tightness and isolation of confined spaces can cause considerable stress. Claustrophobia, anxiety or panic attacks are common reactions to working in cramped, enclosed spaces. This mental strain can lead to mistakes and careless behaviour, which in turn increases the risk of accidents. With the drone, nobody has to enter the cramped space; the pilot controls it from outside.
16. Falling objects
In confined spaces there is a risk of tools or components falling from above. It becomes particularly dangerous when work is carried out on several levels or materials are not properly secured. Even small objects can cause serious injuries when they fall from a greater height. During a drone inspection, nobody stands beneath a work area in the space.
17. Noise and vibration
Confined spaces amplify noise and vibration, which can lead to hearing damage and fatigue. Noise levels that persist over long periods impair concentration and well-being, which increases the likelihood of errors. With the drone, nobody in the space is exposed to the noise.
18. Dust
Dust that accumulates in confined spaces can not only cause breathing problems but also form explosive mixtures with air. Combustible dusts are particularly dangerous, as they can cause severe explosions when they accumulate and ignite. With the drone, nobody breathes in the dust. Dense dust does, however, limit the camera's view, and with combustible dust the operator decides whether the drone may fly.
19. Slips and trips
Slippery surfaces, standing water or tools left lying around increase the risk of slipping or tripping in confined spaces. Because the environment is cramped, a fall can have more serious consequences, as the person cannot break their fall or move out of the way. With the drone, nobody has to walk through the space.
20. Inadequate atmospheric monitoring
In confined spaces it is essential to monitor the concentration of oxygen and potentially hazardous gases continuously. Without suitable measuring equipment, the atmosphere can change suddenly and create acute health hazards before anyone even notices. Incomplete monitoring often leads to unforeseen accidents. With the drone, nobody has to enter the space, and gas-free testing for personnel is not needed. In hazardous (Ex) areas, the operator decides whether the drone may fly.
Every entry you avoid is one risk less
Work in confined spaces involves considerable risks that can become life-threatening within a short time without the right precautions. For such work, employees often have to make complex and costly preparations, including wearing extensive personal protective equipment (PPE) such as breathing apparatus, protective suits and full-body harnesses. Work in confined spaces also requires careful planning and extensive safety measures that take both time and resources.
The Flyability ELIOS 3 offers a way of avoiding many of these risks: it flies into the vessel while the team stays outside. Man entry is not needed, nor are scaffolding, rope access technicians or cranes. The vessel has to be out of service, emptied and released for the drone flight, but the shutdown is considerably shorter because the inspection takes hours instead of days. Learn more about how we inspect tanks and silos by drone.