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This means that breathing low concentrations of freon from a leaking refrigerator or air conditioner over a long period of time is unlikely to have a cumulative effect, and thus few, if any, long term health effects.
in a condo, have an outside ac unit with 'air handler' in my laundry room, with coils I assume freon runs thru from outside (they get cold). Had the fan motor replaced and the tech had to add a pound of freon, commented could be a leak in the inside coils and may need to add more freon in a couple of years.