I think it always means you can install them or not as you wish - but under some conditions you should do an RA to reach that decision. Presumably in the other case you can toss a coin.

Not perhaps  the finest wording.

Less flippantly

lets look at what it all means _ think basically Group 0 locations might uin clude the waiting room and nurses office, and a power cut is likely to lead to no more inconvenience than a school or office other more or less public place.

Group 1 and 2 things may be being done to patient, internally or externally, where the risk to patient is increasing, and the chance of un-authorised equipment being plugged in is low and the wiring will be to a known standard, we hope.

9.3 Definitions
9.3.1 Medical location
Location intended for purposes of diagnosis, treatment including cosmetic treatment,
monitoring and care of patients.
9.3.2 Patient
Living being (person or animal) undergoing a medical, surgical or dental procedure.
Also, a person undergoing treatment for cosmetic purposes may be regarded as a
patient.
.....
Part of medical electrical equipment that in normal use necessarily comes into physical
contact with the patient for the ME equipment or an ME system to perform its function.

9.3.5 Group 0
Medical location where no applied parts are intended to be used and where
discontinuity (failure) of the supply cannot cause danger to life.

9.3.6 Group 1
Medical location where discontinuity of the electrical supply does not represent a
threat to the safety of the patient and applied parts are intended to be used:
(a) externally; or
(b) invasively to any part of the body, except where Group 2 applies.

9.3.7 Group 2
Medical location where applied parts are intended to be used, and where discontinuity
(failure) of the supply can cause danger to life, in applications such as:
(a) intracardiac procedures; and
(b) vital treatment and surgical ope

Mike.

In my opinion guidance is missing on this matter.

The regulation does not use the terms "shall not be installed" as this is quite restrictive. Such a restriction would impair the designer's ability to use equipment appropriately. (I know you could use Reg 120.3 but permitted exceptions are difficult to apply correctly) Hence the wording "not required to be installed" was believed to give the experienced designer opportunity to apply the requirements appropriately.

Just for the record, AFDDs should not be installed on a Medical IT system. 

In my opinion guidance is missing on this matter.

The regulation does not use the terms "shall not be installed" as this is quite restrictive. Such a restriction would impair the designer's ability to use equipment appropriately. (I know you could use Reg 120.3 but permitted exceptions are difficult to apply correctly) Hence the wording "not required to be installed" was believed to give the experienced designer opportunity to apply the requirements appropriately.

Just for the record, AFDDs should not be installed on a Medical IT system.