when is an inner room not an inner room

[GM]

f you had an old business unit located under a railway arch with 6 multi-purpose rooms used for beauty therapy,  etc. which discharge into a small internal lobby area and then from this internal lobby area you had to go through an office room/waiting area to be able to get to the entrance lobby which contains the electric meter in a cupboard and out to a place of safety. The furthest distance to travel would be 17metres from the furthest point to the place of safety. There is automatic smoke detection in each room/lobby.
Max of 15 people only one way out. Complies with all the guidance in relation to max travel dist, small number of occupants and early warning via mains smoke detection.

The only slight concern that it is not inner rooms direct to the outer room, so in theory by having a lobby you lose that close proximity and have 2 doors between the inner and outer room instead of one. My own thoughts are that this layout is okay provided a clear path is kept with adequate emergency lighting, as the distance is okay and early warning is provided by detection and possibly somebody sat in the outside room. So regardless of close proximity the smoke detection will give early warning. Any comments please. I appreciate guidance is only guidance but I have come across situations where it has been used to try to undermine pragmatic decisions

[AnthonyB]

Is the lobby sterile or used such that you'd technically be inclined to count that as a room too?

[GM]

It is a  small lobby and is kept a sterile area by good management. Used for accessing rooms only.

[Dinnertime Dave]

ADB gives the guidance on new/refurbished building and would not allow your senario. However, I would assume that your unit was converted prior to the latest addition of ADB (c was added relatively recently and from experience is ignored). My advice in the Fire Risk Assessement is to record what is there and justify it. Shouldn't be difficult.

Inner rooms
3.10 A room from which the only escape route is through another room is called an inner room. It is at risk if a  re starts in the other room, called the access room (see Diagram 12).
Such an arrangement is only acceptable if the following conditions are satis ed:
a. the occupant capacity of the inner room should not exceed 60 (30 in the case of a building in purpose group 2a (Institutional));
b. the inner room should not be a bedroom;
c. the inner room should be entered directly off the access room (but not via a corridor);
d. the escape route from the inner room should not pass through more than one access room;
e. the travel distance from any point in the inner room to the exit(s) from the access room should not exceed the appropriate limit given in Table 2;
f. the access room should not be a place of special  re hazard and should be in the control of the same occupier; and

[GM]

Hello Thank you to everybody who has replied, your comments have been really helpful, apologies about the delay in acknowledging them