The project developed the diagnostic tools and experimental equipment required to carry out the Pressure Effects on Pyrolysis and Soot Inception project (PEPSI - JOULE Contract JOU2-CT92- 0055). This involved the development of a laser fluorescence instrument to measure polyaromatic hydrocarbons (PAH) semi-quantitatively and a high pressure premix burner. These are now being employed in combustion studies in a number of European laboratories. The issue of soot formation in combustion plants and internal combustion engines is critical, and basic RTD actions are needed to improve understanding of its formation and burn-out. This project was concerned with the influence of pressure on the formation of soot and pyrolysis compounds. The hostile high-pressure environment called for new optical and sampling techniques.