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FIRE SAFETY => Fire Alarm Systems => Topic started by: Mike Buckley on June 15, 2012, 01:21:08 PM
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I am carrying out FRAs on a chain of hotels. Most of the Hotels are looking at a delayed evacuation policy for mobility impaired guests. the issue I have is that they have measured the noise level from the fire alarm and it is in the region of 95dB in the bedrooms and refuge areas. Obviously the minimumof 75 dB at the bed head applies but is there any guide on the maximum level. I am suggesting that the guidance in the Noise at Work Regs is followed and a maximum level of between 80 and 85 dB should be applied. Note I am only suggesting this for areas where guests are expected to remain prior to a decision to evacuate.
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Only max in the code is 120 dB(A). It is unnecessary for such high levels and you would need to watch that the level is not so high that refuge comms become a problem.
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Thanks Colin, I thought as much.
Bearing in mind this is a hotel, I am recommending a maximum level in the refuges of 85 db based on the Noise at Work Regulations. I know Noise at Work does not apply to this situation but at least it gives me a basis to work from as opposed to plucking a figure out of the air.
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Occupational exposure is based on a time weighted average! It's not the sound pressure level but the exposure duration to the sound pressure level. i.e 85 dB(A) over 8 hours exposure is equivalent to 87 dB(A) over 4 hours, 90 dB(A) over 2 hours etc.
120 dB(A) would not be recommended
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Yes I know that the occupational levels are based on a daily average, however I am looking for a reasonable upper level for disabled hotel guests to stay in whilst they are in a place of safety as part of a delayed evacuation policy. We bear in mind that the lower level will be 75 dB however the upper level must be reasonable so that the guests can use the communications required for refuges and can remain in the area without distress. This upper sound level would only apply for areas used as refuges.
I chose the Noise at Work Regs as it does give a figure which gives it a bit of justification.
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Do you what type of sounders are installed Mike?
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It varies from hotel to hotel, some have the horn type, some have the sounder incorporated into the base of a detector in the ceiling. The sounders can either be in the room or in the corridor.
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are the horn types outside the bedrooms and none in the bedrooms.
I find sounders commonly installed and left at max volume (factory set level) especially non addressable ones.
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The horn types can be fitted insode the bedrooms.
Please understand that I am only concerned about the sonders fitted inside rooms and refuge areas where mobility impaired people are expected to remain with the fire alarms sounding. As far as the rest of the hotel is concerned, appart from the reception where again a member of staff is expected to remain to communicate with the guests in the refuges, the maximum sound level can be up to 120 dB.
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LOL ;D
120 dB(A) over 3 seconds is equal to 8 hour exposure to 80 dB(A) and so NIHL would be likely. Good luck with that then
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BTW
That's not even taking into account frequency masking and typical response of human hearing to 1/3 octave band.
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Let's not over complicate the issue. With regard to most of the building where everybody is expected to evacuate the sound levels in BS5839 apply. The only areas I am concerned about are the areas which are used as refuges in a delayed evacuation procedure where people are expected to remain for some time. Given the way some people react to a fire alarm, the idea that people are forced out of the building because they can't stand the noise has some merit. However there are some people who are expected to remain inside the building in a place of relative safety until assistance is available to evacuate them and we can't deafen them.
Hence I propose a maximum limit of 85dB in these areas, which is above the 75dB bedhead level but gives some spread for the engineers to work with. I am going for 85dB as I can point to other regulations as guidance and show I am not just pulling a figure out of the air.
The original question was to ask the panel if anyone knew of any guidance which I have missed.
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65 dB(A) min or 5 dB(A) above background LA90 noise level . Unless sleeping accomodation where SPL should be 75 dB(A)
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Hi Mike
Do you know the make of the "horn types" out of interest?
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Is it wise to have the alarm so loud in protected staircases and especially refuges? BS5839-1 suggests that lower levels are appropriate in staircases?
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Kurnal,
Hence why I am looking for any guidance on the upper level for these areas.
As an aside, one of the rough and ready indicators of excessive noise in a factory is if you need to raise your voice to speak to someone then you need to check the sound levels. As BLEVE has pointed out, the threshold limits I am using as a guide are for an average daily exposure so whilst they will be loud enough to satisfy BS5839 they should not be overly loud for people staying in the area.
BLEVE with regard to the horns I cannot help you.
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Personally I think you only need a relatively quiet signal in the staircases. Possibly no sounders at all with the evacuation signal bleeding in from adjacent spaces. There does need to be a distinctive signal to confirm to people escaping that they should continue making their way out but it only has to be audible, it shouldn't make communications difficult. I'm talking about escape staircases here, not large accommodation stairs that fall within main accommodation spaces.
I could even envisage an acceptable situation where there were no sounders in the escape staircases because they had been replaced by flashing red beacons. Provided all users know what it means, why not?
NFPA72 asks for 15dBA above ambient so, as ambient noise is often almost zero in these spaces, they would be quite happy with very reduced audibility levels, certainly less than 65dBA.
Remember that the objective of the signal in the staircases in not to wake people or to initially alert them or to drive them out with uncomfortable noise levels - these people are already escaping and need the signal merely as continuing confirmation that evacuation is still required.
I've been in too many staircases where it's impossible to think, let alone communicate, because of the ridiculous noise level of the alarm.
Stu
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I test fire alarms every day. I wear ear defenders when measuring the sound output of systems. Even with them, I can be left with temporary residual humming in my ears. One day I forgot my ear defenders. I found that the piercing sound of a sirens actually made me confused! I think that I would have run through a fire to get away from them. That is not intended to be a flippant remark. Refuges, I believe should be around 60dbA only because refuges are normally part of escape routes . Any greater than that might cause disorientation both for the disabled and those who might need to help them. 95dbA in a bedroom is nothing short of brutal! A heart-attack is perhaps a more likely consequence to an alert than the coherent reaction required in a fire situation. I am sure some authority has done some research on this and could offer an alternative more sensible approach than the blind adherence to only a minimum level.
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In the end it is a warning not a fright. If they are awake and can hear it why blast their ears?
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Around 70dB is accepted as being the minimum to awaken your average sleeping person.
The sounder,if mounted directly outside of the bedroom,will drop off between 20dB and 30 dB through the door plus another 12dB if it is 4 metres away from the bedhead so a sounder needs to be in the bedroom BUT doesn't need to be blaring at 95dB to 105dB at 1 metre!!
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The problem is that these are hotels and need to conform to the 75dB at the bedhead. Also we cannot treat the guests as average people because the hotel chain would like the guests to spend their evenings increasing the bar profits.
I would agree with lyn that a lower level would be acceptable in refuges, as the guests would have to be awake to get to them.
As a matter of interest lyn what sound levels are produced by the sirens you are testing?