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 1782 Henry Sidgier was issued a British patent for a rotating drum washer.   Nathaniel Briggs of New Hampshire received the first United States issued patent for a washing machine in 1797.There is very little known of this machine because a fire destroyed the records of it. Nathaniel Briggs of New Hampshire received the first United States issued patent for a washing machine in 1797. There is very little known of this machine because a fire destroyed the records of it.