Where errors, malfunctions or failures in digital systems could increase safety risks, Functional Safety standards and/or Product Liability laws/regulations might not be complied with. Electromagnetic (EM) disturbances can cause interference (EMI) with all digital processors, so must be taken into account for Functional Safety and/or Product Liability. However, it is impossible to do enough EM immunity testing to prove that a digital processor or its software programming is functionally safe enough, and this paper describes the IET's recent guidance on how to deal with this problem.