Inherently safe design is called:
＊to choose adequately various design methods in the which lose or reduce any possible hazard
＊to reduce the necessity that person belongs in hazardous area as much as possible with any technical device in the design.
For example， the machine should be operated in the safe direction not to invite the
hazardous state even in case of misunderstanding, illusion,operation error, or mechanical trouble.
Foolproof function is adopted. A person is hard to be wrong in the system or safe even if operated by mistake. And fail-safe function is adopted. The machine should be operated in the safe direction in any case.