Posted By Alexander Falconer Bob, to my knowledge, there is no specified minimum levels, however it is recommended through one of the BS specifications, alarms should be a minimum of 5 dB higher than the maximum noise levels normally encountered on a typical working day. (obviously to assist personnel in distinguishing the difference from normality and fire conditions). There is no point in specifying a 70 dB level alarm if the normal environment is measured at say 72 dB. Sorry cannot be more precise with regards to the spec, however your fire alarm servicing company may be able to assist

Posted By stephencarey i believe you may find the info required here. http://www.tcea.org.uk/Documents/Fire-alarms.htm

Posted By stephencarey in bedrooms say for a hotel when all furnishings doors closed etc. 75db at the bed head is required. Not sure if i would survive the noise from a deep sleep let alone the fire

Posted By Smiff BS5831 Part 1 is the standard you are looking for. Sounders are available at various SPL outputs and you system should be designed so that they can be heard in the event of an emergency. e.g. if you have small rooms off a coridor, you may have 65dB "compact" sounders in the rooms, but a whopping 105dB sounder in the corridor, or several 90dB ones dotted along the corridor. Factories and warehouses tend to have a few big ones, and office environments have many smaller ones. Risk assess and consider where are people likely to be, and what type of sounder is needed for them to hear it and respond in an unambiguous fashion. Curiously, metal bells are actually having a bit of a renaissance in workplaces where electronic sirens of many kinds are going off all the time. If you have a siren type most have selecable tones to enable them to stand out in certain environments. Don't hesitate to get in touch if you want to know any more.

Posted By RobAnybody Bob, I think the previous British Standard quoted was incorrect. Just Browsing through IHS Tech Indexes as I have to deal with fire related matter & the British Standard you want is : BS 5839 - 1:2002, Section 2, 16 Audible alarm signals. Sorry if I've put anyones nose out. Rob.

Posted By Allen Higginson 65dB - General Levels. 5dB above Ambient noise of more than 60dB which persists for more than 30 seconds. 75dB - At bedheads in systems designed to rise people from sleep. 60dB - In Stairways,areas of no more than 60m2 (cellular offices for example) and areas of "limited extent" (where you are generally getting 65dB apart from a small area where it drops down to but not below 60dB) Levels must not exceed 120dB at any accessible point to the sounder. In places of entertainment or retail outlets where music is likely to be present and above 80dB, the music sholud be muted when the fire alarm goes off (via a relay/interface connected to a contactor for example). In larger installations (production factory for example) you can install secondary mains sounders (earbursters!) to compliment the system, but these must only operate when the production process is running and should isolate when the machinery is not working (fed from common contactor on the same supply circuit as the machinery). Think that (mpostly) covers it!