Messy, this goes right back to two things. The early days of the FP Act and research carried out on behalf of the Home Office in the mid 1980s. When the FP Act was first introduced the chance that you would die from fire if you spent one night in a hotel was approx 10 times that if you spent one night at home. The Act, the designation order and the early guidance was not intended to protect the individual in the room of origin, but only to protect the means of escape for others. ( Thus the person could kill himself if he wanted, same as at home, but not kill anyone else.) Early guidance from the Home Office was that you did not need ANY AFD for this purpose, but all you needed was a break glass manual system. This alone was very effective in reducing fire deaths dramatically-see 1970s fire stats and you will note a step change in fatalities. In practice, as time progressed, people were using AFD in hotels, BUT (and this is really important, Messey) the goal had not changed-the objective was still as set out above. To meet '' the objective'', AFD was put in the corridors only. ( There are still hotels with only the manual systems or only the AFD in corrdiors even today). It was assumed that the AFD in the corridors would operate early enough to allow those beyond the room of origin to escape. Then, around the mid 1980s, the Home Offcie began to ask the question as to whether everyone was sure that the above practice did indeed meet the objective. Specifically, they wanted to know whether the detectors in the corridors would operate early enough to allow escape of those beyond the room of origin before the corridor was smoke logged.
So FRS were contracted to carry out very elegeant research work, using a full scale mock up of a corridor with rooms of at Cardington. They set fires in a room and observed conditions in the corridor, with detectors 15m apart. In general, they found the set up was often ok and people were given early enough warning. However, under certain circumstances, which included no intumescent strips on the doors but just old BS 459-3 doors (which are not used now anyway!!!) they coculd smoke log the corridor before an alarm was given. Further research showed that this depended on the size of the gap around the door. Sods law was that a 3mm gap was worst case, and further work showed that the problem was caused not so much by the hot buyoant gases from the fire but from the pyrolisis of the timber at the head of the door, which resulted in relatively cool, heavy tarry smoke entering the corridor and not having enough bouancy to operate detectors 15m apart.
In truth, this was all very interesting but there was no anecdotal evidence whatsoever of this causing fatalities in hotels, and in any case bedroom doors all have intumescent strips. So, many took the view that it was all very interesting, but so what (including an ex senior fire safety man from your brigade).
There were, howvever, 3 options in dealing with the theoretical problem. One was to rely on the intumescent strips. (Counter arguement was that they might not be fitted.) Two was to ensure that a dtector was always fitted in the corridor close to the bedroom door, as the problem only arose in a lenghty corridor with the detectors 15m apart. (Counter arguement, makes for an awful lot of dtectors in corridors, so might as well go for third option.) Third option was to put detectors in rooms. BIG POINT HERE: These detectors were NEVER intended to protect the person in the room of origin but to protect everyone else to a much better standard.
Ultimately, it was thr 3rd option that was selected. WHY? Because the research showed that even a heat detector in the room would buy about 9 minutes (in the particular reasearch set up) over and above smokes in the corridor alone.
It was purely this work that led to the invention of the Cat L3 system. It does not protect the individual in the room but ensures loadsa warning before the common escape routes are threatened. Thus BS 5839-1 was revised to say (as it still does today), these detectors can be of any type, heat, smoke or CO. Moreover, since the only objective is to warn others before a whacking great fire occurs in the room to the extent that a 30 min FR door is burning away, the detectors can even just be heat detectors on the wall near the door.
Home Office policy was to agree that any detector will do the job , but heat should be chosen because of the need for false alarms (except for disabled rooms and dormitories).This was perfectly logical advice that really still stands today.
Problem was that a lot of fire authorities (including yours) got the entirely wrong end of the stick and though that this new call for detectors in bedrooms was because the objective had changed and we were now protecting the individual in the room of origin. This was not correct and it was some years before the penny dropped and, in the case of your brigade, a chap (who is now a very well respected consultant but was in your fire safety policy group at the time) issued a gudiance note telling the I/Os to stop demanding smoke detectors in bedrooms.
To this day, it remains a mess, Messy, in the sense that a lot of this was lost on new I/Os throughout the country. Many still think the detectors are to protect the occupant. Some accept heat without question. Some accept heat and recommend smoke. Some demand smoke because they dont understand the background.
What about the poor guy in the room of origin? The record shows he doesnt die anyway. In a study carried out in fires over a 5 year period prior to introducing detectors in bedrooms, not a single sould died from fire in any star rated hotel in the UK. Thos who died in non-star rated accommodation were mostly in hostel-like properties, and those who died in the room of origin were committing suicide or were out of it on drugs or alcohol in the main.
So those who do require s/d in bedrooms are trying to save the lives of those who never die anyway---to the detriment of the safety of others, which is compromised by the tendency to ignore alarms because of the rate of false alarms, to introduce staff alarms to delay signals from s/d (so might as well have hd) etc etc.
Ignore hype from people about sophisticated systems ignoring phenomena that cause false alarms, as, in the case of the average system, it is bunkum. In a recently opened hotel, there were 50 false alarms in the first week as a result of steam from en suite showers and kettles.
