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.
In the early 1800s, clothes dryers were first being invented in England and France. One common kind of early clothes dryer was the ventilator, the first one known to be built was made by a Frenchman named Pochon. The ventilator was a barrel-shaped metal drum with holes in it.