Working at Heights in Confined Spaces

People usually think of working at height as only being a risk when working above ground. But you don’t necessarily need to be up high for a fall to occur. Falls from the ground to a level below, even ones inside an existing structure are equally high risk, especially in areas which are not designed for human occupancy and maybe have ingress/egress limitations. As such, the definition of what is, or isn’t, a confined space is not so clear cut.

Confined space environments come in a variety of guises including vats, tanks, pits, pipes, chimneys, silos, sewers, shafts, wells, pressure vessels, trenches and tunnels.

The WHS Regulations define a confined space as an enclosed or partially enclosed space that:

• Is not designed or intended primarily to be occupied by a person; and
• Is, or is designed or intended to be at normal atmospheric pressure while any person in in the space; and
• Is or is likely to be a risk to health and safety from:
• An atmosphere that does not have a safe oxygen level; or
• Contaminants, including airborne gases, vapours and dusts, that may cause injury from fire or explosion; or
• Harmful concentrations of any airborne contaminants; or
• Engulfment, but doesn’t not include a mine shaft of the workings of a mine.

A confined space is determined by the hazards associated with a set of specific circumstances and not just because work is performed in a small space.

Confined Spaces are responsible for multiple fatalities every year across a wide range of industries, from those involving complex plant to simple storage vessels. The risk is often underestimated with those killed not only including operators working in the confined space, but also those who try to rescue them who are often not trained or properly equipped to perform the rescue. Confined spaces, which are sometimes restricted in size, necessitate further consideration by those undertaking rope access or working at height operations, in particular the access, egress and rescue requirements specific to the space and location.

Some confined spaces are easily identified, like sewers, closed tanks used to store chemicals; however some are not so easy to identify. 

A confined space is not necessarily:

1. Enclosed on all sides.
2. Small and/or difficult to working in.
3. Difficult to get in or out of. 
4. A place where people do not work regularly. 

A place that is usually not considered to be a confined space may become one if there is a change in the conditions inside or a change in the degree of enclosure or confinement (which may occur intermittently).

Examples of a confined space. The following locations and places may be a ‘confined space’ where there is a presence of, or a reasonably foreseeable risk of, one of the specified risks to the health and safety of those working in the space:

1. Ducts, culverts, tunnels, boreholes, manholes, shafts, excavations and trenches, sumps, cofferdams, etc.;
2. Freight containers, ballast tanks, ships’ engine rooms and cargo holds;
3. Buildings, building voids;
4. Some enclosed rooms (particularly plant rooms) and compartments within them;
5. Enclosures for the purpose of asbestos removal;
6. Areas used for the storage of materials that are likely to oxidise, e.g. wood pellet  hopper tanks;
7. Unventilated or inadequately ventilated rooms and silos;
8. Structures that become confined spaces during fabrication or manufacture; and
9. Interiors of machines, plant or vehicles.

Specified risk. This means a risk of:

1. Serious injury to any person at work arising from a fire or explosion;
2. The loss of consciousness of any person at work arising from an increase in body
3. temperature;
4. The loss of consciousness or asphyxiation of any person at work arising from gas, fume,
5. vapour or the lack of oxygen;
6. The drowning of any person at work arising from an increase in the level of liquid; or
7. The asphyxiation of any person at work arising from a free flowing solid or the inability to reach a respirable environment due to entrapment by a free flowing solid.

A confined space is determined by the hazards associated with a set of specific circumstances and not just because work is performed in a small space.

Entry into a confined space means a person’s head or upper body is in the confined space or within the boundary of the confined space.

Working in a confined space is a high risk activity and the potential for incidents resulting in fatalities are compounded by the nature of the hazards present. Examples of the key risks include the potential lack of oxygen, high temperatures, explosive environments and the risk of airborne contaminants including gas, fumes and vapours. Other hazards include the risk of engulfment in flood waters, sewerage, grain, smoke or dirt from a trench collapse.

So what can you do?

There are a number of key duties:

1. Avoid entry to confined spaces, e.g. by doing the work from the outside;
2. If entry to a confined space is unavoidable, follow a safe system of work; and
3. Put in place adequate emergency arrangements before the work starts.

You should identify the hazards. Examples include:

1. Flammable substance and oxygen enrichment;
2. Excessive heat;
3. Toxic gas, fume or vapour;
4. Oxygen deficiency;
5. The ingress or presence of liquids
6. Solid materials which can flow;
7. Other hazards not specific to confined spaces, e.g. electricity, noise, collapse or subsidence of or within the space, loss of structural integrity, etc.

How can you do it?

You should assess factors that affect the work:

The precautions required in a safe system of work will depend upon the nature of the confined space and the results of a risk assessment. The main elements to consider when designing a safe system of work, and from which may form the basis of a ’permit-to-work’, are:

1. Supervision;
2. Competence for confined space working;
3. Communications;
4. Testing/monitoring the atmosphere;
5. Gas purging;
6. Ventilation;
7. Removal of residues;
8. Isolation from gases, liquids and other flowing materials;
9. Isolation from mechanical and electrical equipment;
10. Selection and use of suitable equipment;
11. Personal protective equipment (PPE) and respiratory protective equipment (RPE);
12. Portable gas cylinders and internal combustion engines;
13. Gas supplied by pipes and hoses;
14. Access and egress;
15. Fire prevention;
16. Lighting;
17. Static electricity;
18. Smoking;
19. Emergencies and rescue; 
20. Limited working time.

References: 

Safe Work Australia Model Code of Practice: Confined Spaces

IRATA International Topic Sheet No. 20