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 washing machine was designed by H. Sidgier of Great Britain in 1782. The first patented washer in the United States was by Nathaniel C Briggs in 1797. It was a manual device. The first electric washing machine was invented in 1906 by Alva J. Fisher.