Graeme, from one 'thick' engineer to another
I'm sure CT was not having a go at you only! I've noticed that his posts are invariably trying to teach us all not to get so caught up with the precise figures in recommendations.
All of us with a reasonable understanding of fire alarm systems must be able to be prepared to recognise where a variation from a recommendation is not unsafe. In this vein, the recent BS's have included a number of areas of flexibility where, previously, 'codehuggers' would have a field day. For example, limited areas of 60dba SPL in areas otherwise recommending 65dba. (another is mounting heights of mcps)
At the end of the day none of the recommendations should be considered as 'written in stone' for an experienced system designer/installer.
This can go both ways. For example, whilst BS might not recommend a requirement for a minimum db level for areas less than 1m2, if such an area existed and was used as a 'security officers' booth, it is highly likely that a suitable alarm db level would be required.
Commonsense and experience actually determines the requirements in most cases, rather than the BS recommendations.
Therefore should it be considered that the BS recommendations are only provided as a set of rules for those without the necessary experience/commonsense and as an approximate guide to others?