One of the most serious potential hazards is that of asphyxiation. Oil storage tanks have very limited entry points and therefore limited air supply. If proper precautions are not taken to ensure that the access point is kept open at all times to allow air to circulate through the tank, asphyxiation has a high risk of occurring, both for the rescue workers and the ones they are rescuing. This is especially true if the rescue is taking place after any oxygen-consuming activities have been performed inside the oil storage tank. Activities such as welding inside the tank tend to consume the meager supply of oxygen, and this can increase the risk of asphyxiation for the victims and the rescue team. In these cases, rescue teams must take extra steps to ensure that there is a continuous supply of breathing air inside the tank while the confined space rescue is performed.
Other hazards include any dangerous or even toxic chemicals that may be present inside the oil storage tank, and, of course, the risk of drowning if the tank is currently being used to store oil or other liquids. Both of these hazards are seriously exacerbated by the confined nature of the space. The presence of toxic chemicals is hazardous anywhere, but in a confined space with little fresh breathing air to dilute the chemicals, contamination and injury is much more likely. Drowning rescues become more complicated because if there are large amounts of liquids present inside a confined space, there are usually no dry spaces, no places to rest the victim, and no way out but up.
The rope rescue is one of the most popular forms of rescue in a confined space environment such as an oil storage tank. In a rope rescue, rescue workers must be properly trained both in the methods of rescue and extraction and in the use of the equipment used to perform the rescue. They must be able to respond to the threatening situation in a manner that is both timely and responsible.
Equipment used in rope rescue attempts within oil storage tanks may include any number of the many different forms of rescue and retrieval hoists. Rescue teams must be well-versed in the use of harnesses, lanyards, anchor points, snap hooks, lifelines, and carabineers as well as know which of these implements to use in which type of situation. Self-retracting lifeline arrests, also known as SRLs, are some of the most commonly used types of rescue equipment for rope rescues in oil storage tanks. These may be attached to a permanently mounted davit system, if one is present, to allow vertical access to the tank. A portable davit system may also be used if a permanent system is unavailable.