We all know (or should know) that venting refrigerant is a big no-no and can result in trouble from the EPA.
There are many other potential violations, but two that can easily occur if you aren’t thinking ahead are the disposal of mercury and oil.
Mercury is found in fairly large quantities in the bulbs of old thermostats. Instead of ditching these stats, gather them up and return them to an A/C supply house for proper recycling. Most supply houses offer this service.
Refrigerant and Vacuum pump oil are both oils that we often need to drain for one reason or another. Make sure to capture the oil in a pan (or an oil coil cleaner jug) and turn it in to an oil recycler. Many auto parts stores and auto mechanics will have no problem taking it off your hands.
Simple… but easy to get wrong if you don’t pay attention.
No matter what you believe politically we all agree that taking care of the environment is worth doing and something that all responsible adults consider.