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.
Indoor plumbing was invented long before World War 2. According to the related link below, The first patent for the flushing toilet was issued to Alexander Cummings in 1775.. â¦ but Until 1840, indoor plumbing could be found only in the homes of the rich and the better hotels.. World War 2 did not begin until 1939.