Fire Alarms - Seen and not heard?
Fire alarm systems are meant to be seen and not heard, that is unless you need them. 
Recently we have found that we have been carrying out more audibility tests upon systems installed in the last 10-15 years and found without exception that they have failed the audibility www. It seems that within the history of our industry, the sound levels of systems were not paid the attention that they now get.
I remember working for a large fire company that considered the need for an audibility test extra to commissioning the fire alarm, the implications of which was that it was often not an option that was taken up by the clients. The result of which is that lots of sites with perfectly good fire alarm systems will find that they are not noisy enough to meet the standards, and more importantly not noisy enough to encourage people to leave the building.
What the standards say…
In general the standards require that a room less that 60m2 should be 60dB in all areas, anything over that size should be 65dB, and sleeping accommodation should be 75dB at the bed-head, also there are additional requirements for noisy areas where you may find that you need to use flashing beacons to supplement the sounders.
Attenuation (reduce, effect, or value of)
I think that its worth pointing out that modern and now refurbished buildings greatly affect the performance of the fire alarm sounders, on average wall mounted sounders start at about 100-105 decibels (dB), although fire doors can attenuate up to 20-40 dB in my experience therefore you then have to consider the design very carefully indeed, often the choice of preference is base mounted sounders, although the penalty paid by using these ingenious sounders is that the starting level is between 80-90 dB and that they are really designed to cover one space, they can sometimes cover additional areas which have thin partitions of glass or the like.
Third Party Accreditation
Now we have BAFE (British Approvals for Fire Equipment) Scheme ‘SP203′ the industry seem to be cleaning ups its act, which in my view is long overdue. Just to cover myself, the industry will point to the existence of LPS (Loss Prevention Standard) 1014 which has been in existence for a number of years prior to the new BAFE SP203, although my recollections of working within an organisation that has LPS1014 was that the hardly any customers asked for the certification, mostly due to the associated costs, therefore none were issued, bypassing the whole scheme. This brings me back to the headline, they are supposed to be noisy and encourage people to leave, however they should just sit there patiently waiting for the day that a fire breaks out, definitely seen and not heard (except on the weekly tests of course!)
Explanation of terms
I had better provide a brief explanation of what a third party accreditation scheme is, the most famous one that most people have seen is used in the plumbing industry and referred to as CORGI™. The third party has a set of standards that the member companies have to adhear to and audits them to ensure that the company are performing to the laid out standards, in our case the Third Party Standard is BAFE SP203, (one of the BAFE Schemes), WFP are audited by BSI, although there are other auditors who can administer the scheme.
BAFE - British Approvals for Fire Equipment (Modular Fire Alarm Scheme SP203)
BSI - British Standards Institute
If you are choosing who to use then I would recommend that you choose a BAFE registered company as this will give you the assurance that the company has put in considerable effort to meet the standards and will be audited going forward.
