Generally refrigerant is not safe to breath. It can cause the heart to beat irregularly and could cause death if released in a confining space as most boats are. Large chiller rooms have alarms, horns and strobes and emergency
fans to ventilate the machine room in case of a failure and release.
Generally R12 is a cause of ozone depletion and was more or less banned by many country's ages ago, R22 causes less ozone depletion, but should still not be released. IT also has been phased out.
R134A has zero ozone depletion, but is a greenhouse gas. Personally I love greenhouse gases as it is what keeps the planet from being an ice ball.
Generally all refrigerant should be recovered, period. If one was to vent the refrigerant then it should be vented to the outside where it will safely dissipate. If there is no service
valves, then a saddle tap could be added. A ice maker kit with saddle valve would do that cheaply if one did not have the proper gauges, valves, etc.