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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.
A system that is only 10% low in coolant will not operate efficiently and can cost over 20% more on your monthly utility bills. Continued operation of your HVAC units with low coolant can damage your compressor. Freon is 4 times heavier than air and sinks to the ground/floor initially when a leak occurs.