An accident is any unplanned event with the potential to cause injury.
The best way to avoid chainsaw accidents is to understand how chainsaws react in different scenarios such as binding, pinching, cutting on the top of the bar, and cutting with the tip. Be familiar with how the saw performs and handles in each situation.
Be familiar with the forces in the wood you are sawing, to avoid binding, rolling, and falling in unintended directions.
Keep the chain sharp and properly adjusted.
Don't use a chainsaw when distracted or tired.
Notice I have said nothing so far about protective equipment.
Protective equipment does not prevent accidents. It helps to protect you when accidents happen.
Saw kicks back, and brake stops the chain before it gouges your face? That's an accident.
Saw slips and chews up your chaps but not your legs? That's an accident.
Log shifts and binds the saw? That's an accident.
Branch flies up and hits your face shield? That's an accident.
Safety is not a device; it is a state of mindfulness.