There are two main types of fire extinguishers: stored-pressure and cartridge-operated. In stored pressure units, the expellant is stored in the same chamber as the firefighting agent itself. Depending on the agent used, different propellants are used. With dry chemical extinguishers, nitrogen is typically used; water and foam extinguishers typically use air.
The Encyclopedia Britannica, which has been in continuous print since it was first published in Edinburgh in 1768, said today that it will continue with digital versions currently available online. The final set of the 32-volume printed edition remains available for sale on the company's website for Â£890 ($1,400). Scroll down for video
Since 2000, a third edition of the dictionary has been underway, approximately a third of which is now complete. The first electronic version of the dictionary was made available in 1988. The online version has been available since 2000, and as of April 2014 was receiving over two million hits per month. The third edition of the dictionary will probably only appear in electronic form; Nigel Portwood, chief executive of Oxford University Press, thinks it unlikely that it will ever be printed.