Linseed oil unusually large amount of α-linolenic acid, which has a distinctive reaction with oxygen in air. Specifically, the fatty acids in a typical linseed oil are of the following types: Having a high content of di- and tri-unsaturated esters, linseed oil is particularly susceptible to polymerization reactions upon exposure to oxygen in air. This polymerization, which is called 'drying', results in the rigidification of the material. The drying process can be so exothermic as to pose a fire hazard under certain circumstances. To prevent premature drying, linseed oil-based products (oil paints, putty) should be stored in airtight containers. Like some other
User-generated content based on user-generated content, including Wikipedia (2001) and Flickr (2004). The BBC set up a user generated content team as a pilot in April 2005 with 3 staff. In the wake of the 7 July 2005 London bombings and the Buncefield oil depot fire, the team was made permanent and was expanded, reflecting the arrival in the mainstream of the citizen journalist. After the Buncefield disaster the BBC received over 5,000 photos from viewers. The BBC does not normally pay for content generated by its viewers. In 2006 CNN launched CNN iReport, a project designed to bring user generated news