I would recommend an a/c specialist as the system may have moisture in it and need vac'd out.
What neo-ninja is talking about is asphyxiation. Very unlikely that this would happen tbh.
If the system has moisture in it, it will knacker the compressor.
It's needs pressure tested, vacuum'd out and then recharged with the correct weight of refrigerant. Overcharging and undercharging can both be fatal to the system.
I'm implying these techniques from working on buildings so if any a/c auto guys wanna correct me then feel free as this may be different for cars.