Reference(s) for this article..www.ccohs.ca / January 28, 2023
Many workers are injured and killed each year while working in confined spaces. An estimated 60% of the fatalities have been among the would-be rescuers. A confined space can be more hazardous than regular workspaces for many reasons. To effectively control the risks associated with working in a confined space, a confined space hazard assessment and control program should be implemented for your workplace. Before putting together this program, make sure to review the specific regulations that apply to your workplace. All jurisdictions within Canada have regulations dealing with confined space entry. The regulations can vary slightly from jurisdiction to jurisdiction. A contact list for the jurisdictions is available in the OSH Answers document Canadian Government Departments Responsible for OH&S.
More information about the confined space control program is located in the OSH Answers document Confined Space - Program and Confined Space - Atmospheric Testing.
If the confined space cannot be made safe for the worker by taking precautions then workers should NOT enter the confined space until it is made safe to enter by additional means. All confined spaces should be considered hazardous unless a competent person has determined otherwise through a risk assessment.
Generally speaking, a confined space is a fully or partially enclosed space that..
can represent a risk for the health and safety of anyone who enters, due to one or more of the following factors..
Confined spaces can be found in almost any workplace. Confined spaces can be below or above ground. A confined space, despite its name, is not necessarily small. Examples of confined spaces include silos, vats, hoppers, utility vaults, tanks, water supply towers, sewers, pipes, access shafts, truck or rail tank cars, aircraft wings, boilers, manholes, pump stations, digesters, manure pits and storage bins. Ditches, wells, and trenches may also be a confined space when access or egress is limited (but they still have 'blue sky' above). Barges, shipping containers and fish holds are also considered as possible confined spaces.
What are the hazards in a confined space?
All hazards found in a regular workspace can also be found in a confined space. However, they can be even more hazardous in a confined space than in a regular worksite.
Hazards in confined spaces can include..
Why is working in a confined space more hazardous than working in other workspaces?
Many factors need to be evaluated when looking for hazards in a confined space. There is smaller margin for error. An error in identifying or evaluating potential hazards can have more serious consequences. In some cases, the conditions in a confined space are always extremely hazardous. In other cases, conditions are life threatening under an unusual combination of circumstances. This variability and unpredictability are why the process of hazard and risk identification and assessment is extremely important and must be taken very seriously each and every time one is done.
Some examples include..
What should be done when preparing to enter the confined space?
The important thing to remember is that each time a worker plans to enter any work space, the worker should determine if that work space is considered a confined space. Be sure the confined space hazard assessment and control program has been followed. Please see the OSH Answers document Confined Space - Program for more information.
The next question to ask is - Is it absolutely necessary that the work be carried out inside the confined space? In many cases where there have been deaths in confined spaces, the work could have been done outside the confined space!
Before entering any confined space, a trained and experienced person should identify and evaluate all the existing and potential hazards within the confined space. Evaluate activities both inside and outside the confined space.
Air quality testing.. The air within the confined space should be tested from outside of the confined space before entry into the confined space. Care should be taken to ensure that air is tested throughout the confined space - side-to-side and top to bottom. Continuous monitoring should be considered in situations where a worker is in a space where atmospheric conditions have the potential to change (e.g., broken or leaking pipes or vessels, work activities create a hazardous environment or isolation of a substance is not possible). A trained worker using detection equipment which has remote probes and sampling lines should do the air quality testing. Always ensure the testing equipment is properly calibrated and maintained. The sampling should show that..
The results of the tests for these hazards are to be recorded on the Entry Permit along with the equipment or method(s) that were used in performing the tests.
Air testing is often ongoing, depending on the nature of the potential hazards and the nature of the work. Conditions can change while workers are inside the confined space and sometimes a hazardous atmosphere is created by the work activities in the confined space.
For more information see our OSH Answers document on Confined Space - Atmospheric Testing.
How are hazards controlled in confined spaces?
Hazards and risks associated with a confined space must first be identified through a risk assessment. After this is done, a hazard control program can be put in place. The traditional hazard control methods found in regular worksites, which are implemented based on the hierarchy of controls, can be effective in a confined space. The most effective controls are elimination and substitution, if these are not possible or if there is remaining risk, then engineering controls should be considered. Administrative controls should also be put in place to complement other controls. The last measure to consider is personal protective equipment.
However, often because of the nature of the confined space and depending on the hazard, special precautions not normally required in a regular worksite may also need to be taken. Elimination removes the hazard (e.g., finding another way to complete a job without entering a confined space) and substitution replaces a hazard with a safer one (e.g., using cold work methods instead of hot work). An engineering control commonly used in confined spaces is mechanical ventilation. The entry permit system is an example of an administrative control used in confined spaces. Personal protective equipment (such as respirators, gloves, hearing protection etc.) is commonly used in confined spaces as well. However, wearing of PPE sometimes may increase heat and loss of mobility. Those situations should be carefully evaluated. When using PPE, always use as part of a PPE program and be sure to evaluate all possible hazards and risks associated with PPE use.
How is air quality maintained?
Natural ventilation (natural air currents) is usually not reliable and not sufficient to maintain the air quality. Mechanical ventilation (e.g., blowers, fans) is usually necessary to maintain air quality.
How are fire and explosion prevented?
Work where a flame is used or a source of ignition may be produced (hot work) should not normally be performed in a confined space unless..
All flammable gases, liquids and vapours are removed before the start of any hot work. Mechanical ventilation is usually used to
While doing the hot work, the concentrations of oxygen and combustible materials must be monitored to make sure that the oxygen levels remain in the proper range and the levels of the flammable products or combustible materials do not get higher than the prescribed Lower Explosive Limits in your jurisdiction. In special cases, it may not be possible, and additional precautions must be taken to ensure the safety of the worker prior to entering the confined space.
If potential flammable atmosphere hazards are identified during the initial testing, the air in the confined space should be cleaned or purged, ventilated and then tested again before entry to the confined space is allowed. Only after the air testing is within allowable limits should entry occur as the gases used for purging can also be extremely hazardous.
How are energy source controlled?
All potentially hazardous energy source such as electrical, mechanical, hydraulic, pneumatic, chemical, or thermal must be de-energized (or isolated) and locked out prior to entry to the confined space so that equipment cannot be turned on unintentionally. If de-energization is not possible, the hazardous energy must be controlled in a way that eliminates or minimizes worker exposure to the hazards before workers are allowed to enter the confined space. It is important that any method of control other than isolation and lockout must be evaluated and the effectiveness for controlling the hazardous energy must be demonstrated.
Please see the OSH Answers on Hazardous Energy Control Programs and Lockout/Tag out for more information.
What are other safety precautions?
Many other situations or hazards may be present in a confined space. Be sure that all hazards and risks are identified and controlled, for example..