Ethyl alcohol based secondary heat transfer fluids are typically used in ground source heat pumps (GSHPs) in Sweden because of their attractive thermophysical properties and low toxicity. Denaturing agents must be added to ethyl alcohol based secondary fluids, and in Europe, the most commonly used are: propyl alcohol, n-butyl alcohol, methyl ethyl ketone, and methyl isobutyl ketone. In Sweden, only propyl alcohol and n-butyl alcohol can be used because of ...