Ammonia was the working fluid in household refrigerators throughout the early 20th century, where it killed lots of people. Freon was invented as a safe replace

Ammonia was the working fluid in household refrigerators throughout the early 20th century, where it killed lots of people. Freon was invented as a safe replacement for ammonia, and Thomas Midgely was hailed for saving thousands of lives as a result. Albert Einstein invented a new type of refrigerator that didn't use ammonia after hearing of the death of an entire family caused by the explosion of an ammonia refrigerator. It's still used in commercial refrigeration plants, as it's highly efficient.