A scientist at the Morgantown Energy Technology Center, West Virginia, USA, using an argon ion laser to determine the flow of coal ash particles in an exhaust gas model. This is part of a programme which is researching methods of reducing emissions from coal-fired powerplants, a major contributor to global acid rain problems. Other aspects of the project include flue gas desulphurisation and high-efficiency combustion technologies designed to reduce the environmental impact of electricity generation from fossil fuels.