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.
1 King Minos of Crete had the first flushing water closet recorded in history and that was over 2800 years ago. 2  A toilet was discovered in the tomb of a Chinese king of the Western Han Dynasty that dates back to 206 BC to 24 AD.