5. Is CO2 toxic?

At everyday levels of concentration, CO2 is not toxic; rather, it is very useful. CO2 is in the air we breathe, the water we drink and the food we eat. Humans and animals breathe it out, plants need it to grow, and it is a common ingredient in many drinks and candies.

However, when CO2 is more concentrated (10% or greater of the composition of the air that we breathe) it can cause intoxication or poisoning over prolonged periods. The concentrations of CO2 in the pipeline from North Dakota to Saskatchewan are near 95%. At these levels, exposure to CO2 would cause asphyxiation.

But because all gas pipelines - whether carrying natural gas, oil, CO2 or other compounds – carry potentially dangerous substances, strict monitoring and maintenance regulations are in place to ensure they are safely operated. In 13 years of injection there has not been a single injury or death caused by the CO2 pipelined and injected into the Weyburn and Midale oilfields.