[ballenf]

Also flywheels don't give off noxious fumes during failure.

[naravara]

For now. If you want to use one for long term energy storage, though, you're going to need to invent some kind of room temperature superconductor and frictionless surfaces. Who knows whether those would be noxious or not.

[smaddox]

Why? Magnetic bearings and copper work just fine...

[jhayward]

Are you sure? Metal fumes and vaporized epoxies are usually pretty toxic.

[tossandturn]

...or during production (relatively speaking).