Logo - Prévenir les risques professionnels avant d’intervenir en espace clos (E.CLOS)



An allergen is a chemical or biogenic substance that can cause skin or respiratory allergic reactions. Some common allergens are colophony (rosin), formaldehyde, metals (for example, chromium, nickel), organic dyes, epoxy hardeners, turpentine, isocyanates, reactive dyes, tropical wood dusts and biogenic allergens (for example, fungi, animal proteins, terpenes, dust and storage mites, enzymes).

Allergens may be found in many industrial processes, like fermentation, drug production, baking (for example, flour, grain), paper production, wood processing (for example, sawmills), biotechnology (for example, enzymes, vaccine production, tissue culture) and spice production (for example, garlic powder).

Repeated exposure to a substance designated with an S in Schedule 1 of the ROHS may cause sensitization, that is, a reaction in the form of an allergic (immunological) response of the respiratory tract, mucous membranes, conjunctivas or skin.

http://www.ilocis.org/documents/chpt30e.htm (Figure 30.1)



Carcinogens can increase the incidence of malignant neoplasms, reduce their latency or increase their seriousness or number. Carcinogens may be substances (for example, asbestos, formaldehyde, benzene, nickel), lifestyle factors (for example, tobacco use) or situations (for example, rubber manufacturing).


Chemical asphyxiant

Chemical asphyxiants (for example, carbon monoxide, nitrobenzene, hydrogen cyanide, hydrogen sulphide) prevent oxygen transport and the normal oxygenation of blood.

http://www.ilocis.org/documents/chpt30e.htm (Figure 30.1)


According to the Régie du bâtiment du Québec, a client is a person who hires a contractor to carry out work.

Note that the concept of client is similar to that of principal contractor. However, the concept of principal contractor is specific to construction sites.


Combustible dust

Combustible dust is a mixture or substance in the form of fine, oxidizable solid particles, which, at the time of ignition, are liable to burst into flame or explode when dispersed in the air.

http://www.apsam.com/sites/default/files/docs/publications/espaces-clos-guide.pdf(French only)

Confined space

According to section 1 of the ROHS, a confined space is “any space that is completely or partially enclosed, such as a reservoir, a silo, a vat, a hopper, a chamber, a vault, a pit, including a pit and a reception pit for manure, a sewer, a pipe, a chimney, an access shaft, a truck or freight car tank, or a wind turbine blade, and that presents one or more of the following risks due to the confinement: (1) a risk of asphyxia, intoxication, loss of consciousness or judgment, fire or explosion associated with the atmosphere or internal temperature; (2) a risk of being buried; (3) a risk of drowning or being carried away due to the level or flow of a liquid”.




Corrosives (for example, strong acids, strong bases, phosphorus) can destroy exposed body tissues on contact, including the skin, eyes and respiratory tract.


Decomposition product

A decomposition product is a significantly changed organic substance (or matter) on its way to putrefaction (rotting). The decomposition of matter creates new contaminants (for example, carbon dioxide, methane, hydrogen sulphide).


Due diligence

Due diligence refers to the degree of judgment, care and prudence that can reasonably be expected under specific circumstances. Under Quebec provincial law, an employer’s duty of diligence has three distinct and essential components:

  • a) The duty of foresight, which, with respect to occupational health and safety, requires the employer to identify occupational hazards and determine the appropriate preventive measures to take.
  • b) The duty of effectiveness, which requires concrete measures to be taken to ensure worker safety with respect to machinery, training and supervision, as well as monitoring to ensure safety instructions are followed.
  • c) The duty of authority, under which employers have an obligation not to tolerate dangerous conduct and to impose disciplinary measures on employees who fail to obey the rules of caution. Due diligence thus means taking all reasonably practicable precautions and acting conscientiously.



An entrant means a person who enters a confined space. According to section 298 of the COHSR, this person must be a licensed worker who is 18 years of age or older.

A confined space entry is an action that is considered to have occurred as soon as any part of the entrant’s body breaks the plane of an opening into such a space, regardless of whether the intended work activities may or may not require whole body entry, such as atmospheric testing.



Entry permit – Control form – Entry fact sheet

An entry permit or control form is a sheet showing the work procedure in the form of a checklist to make sure the confined space work is done under safe conditions, the work procedure is properly supervised and that nothing has been forgotten. By using an entry permit or control form, workers can check the key points of the work procedure before entering the confined space.

The entry permit or control form should cover the following points (see Table 13 in IRSST report R-955):

  1. Location and description of confined space
  2. Description of work to be done and specific hazards inherent to confined space
  3. Date issued and validity period of permit or control form
  4. Confined space preparation (cleaning, flushing, etc.)
  5. Air quality analyses to be done
  6. Lockout procedure
  7. Ventilation required
  8. Personal protective equipment required
  9. Other necessary equipment (fan, winch, ladder, etc.)
  10. Tools permitted
  11. Presence of supervisor
  12. Workers’ minimum skills
  13. Emergency procedure
  14. Signature of person in charge of work
  15. Signatures of workers

Some companies or employers’ associations use the term “work permit” to cover all aspects of the ROHS.

http://www.cnesst.gouv.qc.ca/publications/200/Documents/DC200-16088web.pdf (French only)


Flammable or explosive

A flammable mixture may catch fire or burn furiously.

For combustion or explosion to occur, the concentration of an explosive mixture has to be between its lower explosive limit (LEL) and its upper explosive limit (UEL) (for example, methane is explosive at a concentration in the air of between 5% [LEL] and 15% [UEL]). An explosive mixture may be a gas (for example, methane, hydrogen) or a vapour (for example, acetone, toluene, turpentine).

The concentration of flammable gases or vapors must be less than or equal to 5% of the LEL.



Under standard ISO 12100, a hazard is a potential source of harm.

In this tool, confined space hazards have been grouped into seven categories:

  • Atmospheric: Poisoning, asphyxiation, explosion/fire.
  • Chemical: Toxic substances, irritants, corrosives, carcinogens.
  • Biological: Decomposition/degradation products, sediments, residues, slow oxidation, pathogens, allergens, animals.
  • Falling: Falls from heights, falls on same level, falling objects.
  • Mechanical: Moving parts, sharp parts, parts with potential energy, flying parts, outside traffic, structural failures, mobility of confined space.
  • Physical: Electricity, heat, optical and ionizing radiation, noise, vibration, engulfment, drowning.
  • Ergonomic: Physical exertion, work posture, heat constraints, inadequate lighting/reduced visibility, atmospheric pressure, psychology/stress.



Under standard ISO 12100, harm is physical injury or damage to health.



Irritants (for example, strong acids, strong bases, solvents, oils, aldehydes, ammonia, nitrogen dioxide, phosgene, chlorine, bromine, ozone) cause tissue inflammation. Skin irritants may cause reactions like eczema or dermatitis. Severe respiratory irritants might cause shortness of breath, inflammatory responses and edema.

http://www.ilocis.org/documents/chpt30e.htm (Figure 30.1)


According to section 1.1 of the SCCI, “lifeline” means a synthetic fibre rope, a steel wire rope or a strap attached to an anchorage system and used to guide a rope grab. A lifeline is used in a “fall arrest connecting device,” defined as all equipment used to secure a safety harness to an anchorage system.



According to section 188.2 of the ROHS, lockout, or, failing that, any other method that ensures equivalent safety must be applied before undertaking any work in the danger zone of a machine (for example, maintenance, inspection). The purpose of such work methods is to control hazardous energy associated with the equipment in order to prevent any accidental release of energy and therefore any possible injuries.

More specifically, under section 188.1 of the ROHS, lockout means an energy control method designed to install an individually keyed lock on an energy isolating device or on any other device allowing for the control of energy such as a lockout box.



Most pathogens are microscopic organisms that are invisible to the naked eye. They are found everywhere, in living beings, in the environment and in workplaces. They can be divided into broad categories: bacteria, microscopic fungi, viruses, protozoa and prions. Pathogens can cause disease in humans (for example, asthma, flu, tetanus) and may be hazardous to workers.



Preventive measures

Under standard ISO 12100, a protective measure is a measure intended to achieve risk reduction.

Following the risk evaluation, risks deemed unacceptable must be reduced. In this tool, preventive measures are grouped into the following categories (by order of effectiveness):

  • Eliminate risk at the design stage
  • Eliminate the need to enter the confined space
  • Attenuate the hazard associated with the process
  • Use engineering controls or collective protective equipment
  • Establish work procedures
  • Use personal protective equipment
  • Other


Principal contractor

According to section 1 of the AOHS, principal contractor means the owner or any other person who, on a construction site, is responsible for the carrying out of all the work.

Note that the concept of principal contractor is similar to that of client. However, the concept of principal contractor is specific to construction sites.


Qualified person

According to section 297 of the ROHS, qualified persons are those who, by reason of their knowledge, training or experience, are able to identify, assess and control the dangers (hazards) relating to an “enclosed area” (confined space).

The SCCI does not describe “qualified persons” with regard to confined spaces. It says that the principal contractor, together with the employer, must identify, assess and control hazards associated with a confined space.



Qualified workers

According to section 298 of the ROHS, qualified workers are 18 years of age or older and those who have the knowledge, training or experience required to do work in an “enclosed area” (confined space).

The SCCI does not describe “qualified workers” with regard to confined spaces. It says that the principal contractor, together with the employer, must identify, assess and control hazards associated with a confined space.



Risk analysis

Under standard ISO 12100, a risk analysis is a combination of the

  1. specification of the limits of the machine
  2. hazard identification
  3. risk estimation


Risk estimation

Under standard ISO 12100, “risk estimation” means defining the severity of harm and the probability of occurrence of that harm. This work may be done with the help of a risk graph or risk matrix, for instance.


Risk evaluation

Under standard ISO 12100, “risk evaluation” is a judgment, on the basis of risk analysis, of whether the risk reduction objectives have been achieved. In other words, it is a judgment intended to determine whether the estimated risk is acceptable. Acceptability refers to criteria that must be set ahead of time.


Simple asphyxiant

A simple asphyxiant (for example, methane, ethane, hydrogen, helium, nitrogen) is a physiologically inert gas that acts primarily by displacing airborne oxygen and that can cause a decrease in the percentage in volume of airborne oxygen. The minimum percentage of oxygen allowed in confined spaces in an establishment is 20.5% (s. 302 of the RROHS). It is 19.5% in confined spaces located on a construction site (s. 3.21.2 of the COHSR).


Slow oxidation

Oxidation is the chemical action of a body combining with oxygen to form an oxide. The rusting of iron in damp air is an example of slow oxidation. Oxygen in the confined space is used up as a result.

http://www.cnrtl.fr/definition/oxydation (French only)



Under standard ISO 12100, risk is a combination of the probability of occurrence of harm and the severity of that harm.


Residual risk

Under standard ISO 12100, residual risk is the risk remaining after protective measures have been implemented.



Sediment consists of particles suspended in a liquid, the air or ice, which settle due to the force of gravity, often in successive layers, or strata. A sediment is characterized by its nature (physical and chemical composition), origin, particle size distribution, elements and potential toxicity.


Toxic material

Toxic materials are substances (for example, solvents, organic materials, metals), which through inhalation, ingestion or skin contact may cause various acute, chronic, carcinogenic or fatal physiological reactions in a target organ.



The term “work in confined space” (or confined space work) in this tool includes the entry phase, but also all related activities, such as the preparation phase, supervision and rescue. Work may include several distinct tasks to be done in the confined space.