For example, for the Gases under pressure hazard class, the hazard categories are Compressed gas, Liquefied gas, Refrigerated liquefied gas and Dissolved gas. These classes relate to the physical state of the gas when packaged and do not describe the degree of hazard.
1 In 1596, a flush toilet was invented and built for Queen Elizabeth I by her Godson, Sir John Harrington. 2  The first patent for the flushing toilet was issued to Alexander Cummings in 1775. 3  During the 1800s, people realized that poor sanitary conditions caused diseases.
The first reliable (handpowered) dishwasher was invented in 1887 by Josephine Cochrane with the help of George Butters and was unveiled at the 1893 Chicago World's Fair. Cochrane was quite wealthy and never washed dishes herself; she reportedly invented the dishwasher because her servants were chipping her fine china.