Confined Space Hazards and Precautions

Sometimes the working environment in itself is a source of risk. One key cause of this is confined space such as elevator shafts, underground storage tanks and reservoirs, crawl spaces and basements, sewers and conduits, welding and soldering tents.


Confined Space Hazards and Precautions


They are often dark, oppressive and poorly ventilated, thereby creating specific risks such as suffocation or fire hazards.

What Is Confined Space?

A confined space is a area that is closed off or half-open, often with a narrow entrance and little room to move. The means of escape are generally limited. Confined spaces are not suitable to work long periods of time in.


They are particularly dangerous due to poor lighting and ventilation, the possible presence of dangerous substances or fumes or a dangerous atmosphere and the often high level of relative humidity. Conduits and cables are often found in an unexpected place, causing people to trip and fall.


Risk of Confined Space

Working in a confined space often involves a number of risks such as fire and explosion, suffocation and poisoning, electrocution and tripping or falling.


Fire Risk and Risk Of Explosion

The odds of fire or an explosion occurring are greater in a confined space; the lack of ventilation can cause gases to build up and the lower explosion limit is easily reached. You should also be careful in spaces containing flammable substances.


Even when a space looks clean, the floor or the pores of the walls can still hold substances. Also take into account that the substances that are present may ignite spontaneously, e.g. in a petroleum storage tank, where the iron of the tank and the sulfur in the oil may combine to form iron sulfide which, when drying, may combust spontaneously at room temperature.


The likelihood of fire and explosion increases with activities involving fire or sparks such as welding and cuffing and activities involving supply pipes that can leak.


Danger Of Suffocation

In a confined space you have to be acutely aware of the danger of suffocation. Inadequate ventilation quickly results in oxygen deficiency, which is hard to sense. Keep in mind that e.g. Welding uses a lot of oxygen, causing levels to decrease even more rapidly.


The presence of fire, noxious fumes and chemical or biological reactions can also make it hard to breathe and lead to suffocation.


Risk Of Poisoning

The Risk of poisoning is higher in confined spaces than in any other environment. Even in small quantities the concentration level of a dangerous substance can quickly reach critical levels due to poor ventilation and the limited dimensions of the confined space.


Watch out for noxious gases or fumes produced in the space itself e.g. through the removal of old layers of paint.


Risk Of Electrocution

The risk of electrocution is greater than normal in confined spaces because of the higher level of humidity often found there. They are often damp by nature and temperatures are higher because of poor ventilation, causing those present to sweat more. The high humidity increases conductivity.


Consequently, you should always use the lowest tension possible. Be particularly careful when the confined space itself consists of conductive material. For example, an entire steel tank can be put under tension if the electrical cable of the tool you’re using is defective.


Tripping and Falling

Wet floors, trailing cables and the lack of room to maneuver considerably increase the risk of tripping and falling.


General Measures and Precautions

Prevention In Confined Spaces

Because of the increased risk, it goes without saying that additional preventive measures are called for when working in a confined space. Who is allowed to work in a confined space? How long can you stay there and what should you wear? Etc. There is a specific rule for every risk.


Precautions To Be Taken Beforehand

Before you are allowed to work in a confined space, you must be certain that the confined space is sufficiently accessible. The exits must be kept unobstructed, space must be clean and dry and the supply pipes must be disconnected or secured by blind flanges.


Space must be fenced or warning signs put in place. You should also have the necessary work permit and the presence of a safety standby is required. Work in confined spaces is unsuitable for persons under 18 years of age.



Bring in at least 2 people for activities in confined spaces: one person who works inside the confined space and a partner who acts as a safety standby outside.


The rope of the safety standby should be clearly defined, either to look out to contact the safety services in the event of an emergency or if anyone is authorized to effect a rescue with relevant training and equipment should be provided.


The safety standby supervises the activities and maintains contact with the person working within the confined space. He must be present at the entrance to the confined space at all times. He also checks the ventilation system. If something goes wrong, the safety standby raises the alarm and alerts the emergency services.


Amount Of Time Spent In The Confined Space

It goes without saying that the amount of time spent in a confined space should be kept down to a minimum.



Before you can start your activities in a confined space you need a valid work permit, which should be explained in detail by someone in charge.


Types Of Confined Spaces

 Pipeline, Pumping Station


 Septic Tank

 Sewage Digester

 Storage Tank

 Sewer, Utility Vault




 Ventilation Ducts

 Crawl Spaces

Types of Confined Spaces

Confined Space Entry Requirements

Before entering in a confined space ensure the following:

  • Hazards have been identified.
  • Risks have been assessed.
  • Control measures have been implemented.

All the people required to enter into confined or enclosed spaces shall be instructed as to the nature of the hazards involved, the necessary precautions to be taken and the use of protective and emergency equipment required.


Entry Requirement

  1. Supervisor
  2. Standby Personnel
  3. Rescue Personnel
  4. Entrant

The Permit-Required Confined Space Entry Program Must Be Reviewed

Entry Permit Must Have

    • Names authorized entrants
    • Describe the location
    • Details the work to be done
    • Records test result
    • Lists control measures
    • States any chemical agents being introduced
    • Name of standby personnel (role)
    • Rescue arrangements
    • Other precautions (warning sign etc)
    • PPE
    • Period of time the permit is valid for
    • Hot work permits (welding, cutting etc)

Confined Space Hazards and Precautions Control Measures

Confined Space Hazards

▪ Hazardous substance (oxygen deficiency, flammable, toxic etc)

▪ Biological hazard

▪ Engulfment by solid or liquid

▪ Electrical shock

▪ Entanglement in machinery

▪ Falls

▪ Noise

▪ Extreme temperatures

▪ Lack of lighting

▪ Psychological stress


Measurements are of crucial importance when working in a confined space in order to verify whether the level of oxygen remains adequate and to make sure there is no abnormal build-up of gases or substances that may be dangerous in their own right or may deplete the oxygen supply.


All measurements must be taken by qualified personnel. They must be performed regularly, sometimes in several places at the same time or sometimes on a continuous basis, as circumstances can change quickly due to air movement or changes in temperature.



Before entering a confined space you need to make sure there is an adequate supply of fresh air through a system of general ventilation or local air extraction. Permanent ventilation must be available in the confined space.

Precautions Against Electric Shock

Take special precautions if your work requires the use of electrical tools in a confined space. It is advisable that machinery use a low voltage supply e.g. less than 50V AC or 120V DC to eliminate the risk of electrocution.


The electrical installations must be earthed properly and the walls of the confined space itself must also be earthed if they are made of conductive material. Obviously never use machines with damaged cables.


How To Keep From Tripping and Falling

In order to keep from tripping and falling, there needs to be adequate lighting, an appropriate workplace layout and good housekeeping. These are factors which contribute to a higher degree of safety. Protective footwear is also indispensable.


Additional Protection

Special Cases

Sometimes specific work needs to be done in confined spaces that involve increased risk or certain tools such as welding equipment or a cutting torch have to be used.


Moving Parts

Sometimes a confined space contains moving parts, e.g. a tank with a mixer. If these parts start to move while someone is in the tank, then this can be fatal. That is why moving parts should never be activated as long as someone is in the tank. In order to guarantee this, you can for example immobilize the activation switch with a lock.


Oxygen and Other Gas Bottles

The use of oxygen or other gas bottles in a confined space involves increased risk because any leak immediately leads to a higher concentration. Consequently, you need to check all the hoses for leaks prior to use.

Place the bottles outside the confined space and bring out the torches and hoses during breaks or when the work is finished.


Welding and Cutting Activities

Remove or cover all flammable substances during welding and cutting activities in order to eliminate fire risks. Pay special attention to oxygen leaks. Always keeps fire extinguishing equipment within easy reach.


Welding fumes and welding smoke must be evacuated through a local extraction installation and electric welders must use a safe voltage supply.


Flammable Production

Sometimes, it is necessary to use flammable and toxic products in a confined space, e.g. paint or solvents. It goes without saying that extra care should be taken in these cases. That is why wearing independent respiratory protection is mandatory.


You must also keep the space well ventilated in order to keep the concentration of flammable gases below a certain percentage of the lower explosion limit-this percentage varies from one country to the other. Space must not be sealed off immediately as the hardening process of some types of paint uses up oxygen.


Keep the space well ventilated for several days after the work is finished to keep the concentration of flammable gases low. Space and the equipment used must be properly earthed in order to exclude sparks due to static electricity.


Confined Space Safety Equipment List

    • – Safety harnesses
    • – Descent control devices
    • – Fall arresters
    • – Rapid rescue system (includes safety lines)
    • – Gas detectors
    • – Electronic sensor type, i.e. Exotox/Gastech
    • – Self-contained breathing apparatus – Air supplied
    • – Self-rescue type
    • – Filter type
    • – Safety helmets
    • – Safety boots
    • – Eye protection
    • – Hearing protection
    • – Hand protection
    • – Safety Torch
    • – Communication devices
    • – Fire extinguishers
    • – Others