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
The earliest dictionaries in the English language were glossaries of French, Spanish or Latin words along with their definitions in English. The word dictionary was invented by an Englishman called John of Garland in 1220 â he had written a book Dictionarius to help with Latin diction. An early non-alphabetical list of 8000 English words was the Elementarie, created by Richard Mulcaster in 1582.