It might have been ammonia.
When did they stop making ammonia refrigerators?
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Ammonia was once widely used as a refrigerant in household refrigerators, but it was eventually phased out due to safety concerns. Pure ammonia gas is highly toxic to humans, and even small leaks could pose a significant threat.
The Shift to Alternative Refrigerants
In the 1930s, Du Pont developed chlorofluorocarbons (CFCs) as a non-toxic replacement for ammonia. CFC-12 (dichlorodifluoromethane) was particularly popular due to its similar boiling point to ammonia. This marked the beginning of the end for ammonia refrigerators in household use.
Large-Scale Industrial Use
While ammonia is no longer used in household refrigerators, it is still used in some large-scale industrial refrigeration systems, such as packing houses and cold storage facilities. This is because the risks associated with ammonia leaks are mitigated by proper safety measures and equipment design.
In summary, ammonia refrigerators were largely phased out in the mid-20th century due to safety concerns and the development of alternative refrigerants.