How should I safely dispose of an old phone with a swollen battery?

If you can do so without handling the phone more than necessary, move it to a cool, dry outdoor location on concrete or another nonflammable surface, away from buildings and combustible materials. Don’t place it in a sealed container, and don’t transport it until the disposal facility tells you how they want it handled. If it starts heating, smoking, hissing, or producing an odor, move away and call emergency services.

The safest approach is to call your local hazardous-materials or non-emergency fire-service line for instructions. Tell them the phone has a visibly swollen lithium-ion battery. They can direct you to the right collection point or arrange safe handling; ordinary recycling and trash services may not be equipped for it.

Treat it as a real lithium-battery fire hazard. Don’t charge it, turn it on, press on the swollen area, puncture it, or throw it in household trash or a normal electronics-recycling bin. Since the battery is built into the phone, don’t try to remove it unless a qualified technician says it can be done safely. Keep it away from heat and anything flammable, and contact a local hazardous-waste facility or battery-recycling center first to confirm they accept swollen devices.