De-learning – a challenge for risk management.

Risk analysis professionals and policy-makers may wish that the state of knowledge is continuously improving – that the body of information on accident prevention is ever expanding – as if obeying a fundamental law of nature. A case is presented which shows that the opposite can occur. That awareness of hazards learned the hard way after accidental explosions with great loss of life, careful investigation of causes and dissemination of findings in scientific journals, can slip into oblivion and disappear from the body of generally recognized expert knowledge. Wood pellets are the most common form of woody biomass, and the fuel is widely considered CO₂-neutral. The fast-growing wood pellet sector struggles with smoldering fires in storage silos. The fires are difficult to deal with. Water cannot be used. This has led to new techniques for firefighting which employ inert gases. Nitrogen and carbon dioxide are common inert gases for firefighting, and they are commercially available in large quantities. Unfortunately, the release of carbon dioxide can create electrostatic sparks. Because smoldering fires create flammable pyrolysis gases, the application of carbon dioxide for quenching of a fire may lead to explosion resulting in loss of life. The presentation offers evidence that information on the hazardous electrostatic properties of carbon dioxide has gone unnoticed in popular wood pellet industry handbooks, reference works and even in internationally recognized standards and codes. The presentation also covers some of the foot dragging and bureaucratic difficulties that are experienced when bodies such as the National Fire Protection Agency (NFPA) are notified of shortcomings in their publications, leading to slow progress in improvement in standards and codes.