Confined spaces at heights

Small and enclosed areas are not only found in underground industries like the mining sector. There are a number of above-ground environments that are also considered confined, including silos, water tanks, wind turbines, manholes and storage bins.

These are often accessed for maintenance, installation and restoration, and can require work to take place more than 10 m above the ground. They are, in fact, doubly hazardous, as the requirements both of work at height and of tight spaces need to be factored into safety considerations.

Access and entry

Confined spaces are generally not designed for everyday use and tend to have openings that are only large enough for people to get in to perform certain jobs. These often require the use of rope access techniques and, in some cases, even the erection of scaffolding within the space. Importantly, work at height does not start only when inside the confined space – the requirements need to be considered right from the point of entry.

There is a range of specialised equipment that can be used when accessing a confined space, including tripods and mechanical lifts. This equipment is most often used in conjunction with the personal rope access equipment that is utilised inside the space. With the particular hazards involved in these environments, training is required in the risks of confined spaces, and safe access is required.

Exit points

Confined spaces often only have one single access point for both entry and exit – a factor that needs to be taken into account during safety planning. The means of entry/exit can also differ from site to site. For example, grain silos have an access point on the top, but also have an opening at the bottom where the grain is pumped out onto a conveyor. The bottom opening, however, is often too small to be accessed by a person wearing full protective equipment and therefore cannot be counted on for a quick escape.

It can happen that a rope access technician gets stuck on their working ropes, is unable to ascend back up to the entry point and becomes trapped. This can happen quickly and, unless provision has been made to retrieve the technician by other means, it could lead to death. Because of this, it is recommended that well-formulated site and rescue plans be completed before any work is conducted.

Hazards

Significant hazards are involved in working in a confined space, such as:

Excessive heat

Temperatures in a confined space can become far higher than in a normal place of work. Individuals exposed to these conditions can experience heat exhaustion, fainting and severe dehydration. This can be exacerbated by the physical effort required while in the confined space. It is therefore important to monitor fluid intake as well as the amount of time spent in the confined space.

Toxic gas, fumes or vapour

Some tanks and silos contain material that generates toxic gases and fumes, such as petrol storage tanks. These gases can build up in the area and become trapped if there is inadequate ventilation. It is imperative that a gas monitor be used to measure the presence and concentration of gases before workers enter a confined space, and that care is taken to use the appropriate personal protective equipment and breathing apparatus before entering.

Toxic gases, fumes and vapours can cause fainting, asphyxiation or immediate death. The presence of these gases also makes the area oxygen-deficient, meaning that a person would have to substitute or supplement their oxygen with specialised breathing apparatuses. Some gases can be combustible; the slightest spark can create a fire or even an explosion. It is therefore important to ascertain if any of these gases are present if the work requires the use of welding or electrical equipment.

Working at heights in a confined space is a very specialised task. Those involved must be competent in each environment, separately, as well as able to deal with the specific challenges that occur when they are combined. Additionally, the correct protective equipment for the scope of the work and area being accessed is required.

If there is any uncertainty on any of these points, it is best to consult with an expert who can advise on the risks and hazards specific to the location and provide the best solution.