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 Romans invented indoor plumbing. It took America in the late 20th century to uninvent it. The fateful year was 1994, when the federal government mandated that all toilets manufactured and sold in the U.S. have tanks no bigger than 1.6 gallons. It was the new prohibitionism. Gradually over the coming years, the toilets stopped working as they once did. The reality was slow to dawn on Americans, who are rather used to improvement in consumer products, not slow depreciation, devaluation, and even destruction. Over time, the problems were legion.