At low concentrations carbon dioxide is harmless. It is in the air we breathe. At room temperature CO2 is a colourless, odourless gas and does not support combustion. CO2 is a by -product of living organisms i.e it is produced from humans and oxygen-using bacteria. The concentration in fresh air is about 350ppm. However, at elevated levels, CO2 can be harmful and cause dizziness, headaches and asphyxiation. CO2 can accumulate in work areas such as trenches and cellars, i.e. in any confined space. For CO2 to be dangerous to life, it must be elevated to levels of v/v 50%. It is a very common hazard encountered in confined spaces. According to the law, CO2 is classed as a substance hazardous to health and regulations in its safe use must be adhered to according to Substances Hazardous to Health Regulations 2002 (COSHH). There are workplace exposure limits (WELs) for CO2; the HSE has set this as 5000 ppm for long term exposure and 15000 ppm for short term exposure. CO2 is considered a toxic hazard and so needs to be controlled. We need oxygen to breathe so when CO2 displaces oxygen there are then risks to health.
Carbon Dioxide has many domestic and commercial uses. It is used in the fermentation process of beer and wine making. It is also routinely used in the oil industry to decrease the viscosity and aid in the extraction of oil from fields. Dry ice (solid carbon dioxide) is used to refrigerate foods. The inhalation of elevated levels of CO2 can increase the acidity of the blood and cause adverse effects on the respiratory, cardiovascular and central nervous systems. So, it is important that work areas are frequently monitored, especially confined spaces and the CO2 level controlled as set out in COSHH. Carbon Dioxide can also be a by-product of certain industries, for example, coal fired power stations which can produce up to 30 000 te/day of CO2. CO2 is a by-product from the energy, pipeline and chemical industries.
It is vital to contain and not allow the release of CO2 to become a hazard. Carbon Capture and Storage (CCS) is a low carbon technology that captures CO2 and transports it offshore for safe underground storage. CO2 is transported by pipeline or via tankers from the capture site to an offshore installation. The CO2 is then stored in a deep geological formation such as a saline aquifer, or a depleted gas or oil well. It is contained so it cannot leak out to the surrounding environment.
Eventhough carbon capture and storage needs to be regulated, it must be considered that it is an emerging process that is not specifically addressed by GB law. Even though CO2 is not listed as a dangerous substance under the Control of Major Accident Hazards Regulations 1999 (COMAH), these regulations do apply to the CSS process chain. Other regulations that are applicable to the CSS process chain include the Pipelines Safety Regulations 1996 (PSR) and the Offshore Installations (Safety Case) Regulations 1995 (OSCR). As CSS is a relatively new process, there are no large scale projects operating. However, future CSS operators will need to comply with existing health and safety law to ensure the safe capture, transportation and storage of CO2 so that it is not harmful to workers in the immediate vicinity or to the public or the environment.