Freon

Freon is the trade name used for a group of chlorofluorocarbons that are used in refrigeration systems (fridges, air conditioning, etc.). The most commonly used are CFC-11 (CCl₃F) and CFC-12(CCl₂F₂).

They have been implicated as one of the causes of the ozone layer depletion problem. They are no longer being produced and while it is not illegal to own systems using them it is recommended that these be modified to use an alternative. R-134a is the name of the main US alternative.

% host -t txt freon.artificial.com
freon.artificial.com descriptive text "Anesthetized monkeys exposed to 25,000 ppm or 50,000 ppm [of freon] for 5 minutes had cardiac arrhythmias including tachycardia and decreased contractility (U.S. EPA 1983)."
freon.artificial.com descriptive text "[C2Cl3F3]"

As as side note, I'm the person who named that machine. It's a NeXT slab, and we were tossing around possible hostnames suitable for such a sweet machine. I came up with freon because

1. it's cool
2. it's old-fashioned
3. it's not used much any more
4. ... and yet, it's superior to its modern replacements

(Anyone who disagrees with that last point should go take a drive in a big boat of a freon-cooled-A/C american car.)