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 first edition of A Greek-English Lexicon by Henry George Liddell and Robert Scott appeared in 1843; this work remained the basic dictionary of Greek until the end of the 20th century. And in 1858 was published the first volume of the Deutsches WÃ¶rterbuch by the Brothers Grimm; the work was completed in 1961.