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 considered confined too, 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 over 10m from the ground. That means they are, in fact, doubly hazardous, as both the requirements of work at height, and tight spaces need to be factored into safety considerations.
Confined spaces are generally not designed for everyday use, and tend to have openings that are only large enough for people to get in and 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 then utilised while inside the space. With the particular hazards involved in these environments, training in both the risks of confined spaces, as well as safe access is also required.
As mentioned, confined spaces are not generally designed with daily use in mind. That means there is often only one single access point for both entry and exit, which needs to be taken into account in safety planning. The means of entry/exit can also be different 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 conveyer. 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.
A situation can occur where 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 certain death. Because of this, it is recommended that well-formulated site and rescue plans be completed before any work is conducted.
There are significant hazards involved when working in a confined space. Below we address two key risks that could be present:
A confined space can reach temperatures that may not occur in a normal place of work. When individuals are exposed to these conditions, they can experience heat exhaustion, fainting and severe dehydration. This can be exacerbated by the physical effort required while in the confined space. For this reason, it is important to monitor fluid intake as well as the amount of time spent in the confined space.
Some tanks and silos contain material that generates toxic gases and fumes, as in the case of 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 gasses before entering any confined space, and that care is taken to use the appropriate PPE and breathing apparatus before entering.
Toxic gases, fumes and vapours can cause fainting, asphyxiation or immediate death. The presence of these gasses also makes the area oxygen deficient, meaning that a person would have to substitute their oxygen with specialised breathing apparatus. Some gasses can also be combustible, and the slightest spark could create a fire or even an explosion. It is therefore important to ascertain if any of these are present if the work requires the use of welding or electrical equipment that could generate a spark.
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, then it is best to consult with an expert who can advise on the risks and hazards per location and provide the best suited solution in terms of equipment training competence required to access and work in the area.