More recently I have been using a relatively-new technique (proton transfer reaction mass spectrometry, or PTR-MS) for making measurements of other types of volatile organic compounds (e.g. hydrocarbons, oxygenated hydrocarbons) in the atmosphere. These compounds play an important role in the photochemical production of ozone in the troposphere. Currently we have one ground-based instrument, which is deployed at the Weybourne Atmospheric Observatory for long-term observations; and one aircraft instrument, which operates during intensive flying campaigns on the UK atmospheric research aircraft (FAAM). In recent years these campaigns have included deployments in the Azores (ICARTT, 2004) and West Africa (AMMA, 2006).