Fire Alarm Sound Level in Toilet

[JFW]

The Fire Alarm in smallist factory / office (18000 square feet) was installed and signed off back in 2000.

I have taken over responsibility for it and during a weekly fire alarm check, I used a noise meter to check the sound levels throughout the building. With the exception of one area, the sound exceeded 65 db.

However in a toilet, I measured 57db. Does the alarm system comply with BS 5839-1 as the normal background level is 44 db ?

BS 5839-1 states :-

Sound levels should generally be 65dBA or 5dBA above persistent background noise levels. This may be reduced to 60dBA in rooms smaller than 60m2, in stairwells or in specific limited points of the building.

The toilet is less than 60m2 and the alarm is over 5 db above persistent background noise. So does this comply, as the wording in BS 5839-1 is not exactly clear ?

What do you think ?

[David Rooney]

The human ear can't differentiate 3db.

I think you need to apply a bit of common sense, presuming you haven't got music being piped in or anything else that's likely to mask the alarm (such as particualrly noisy hand dryers going to keep going for more than 30 seconds) then if you (as the responsible person) feel the alarm level is adequate it should be recorded as a variation from the Standard.

If you feel there is a chance the nearest sounder may fail/be drowned out by noisy machinery etc etc then consider installing an additional sounder - and beacon to meet part M requirements.

[Phoenix]

The level of 57dB is acceptable provided that the sound of the fire alarm is clearly distinguishable.  To quote from 5839, "in an office building, it might be judged that, say, sound pressure levels of 57 dB(A) could be accepted in a number of cellular offices, since to achieve the 60 dB(A) recommended in this standard, would necessitate a large increase in the number of sounders (and hence in cost), when the difference of 3 dB is only just perceptible to occupants." 

For "cellular offices," read "wcs".

Being in a toilet can lead to problems as there are likely to be background noises.  If the room is a shower room as well as a wc then you may find that the fire alarm cannot be heard above the noise of the shower.  If it is just a wc then the noise of the flush may well drown out the noise of the fire alarm but the flush only lasts for a maximum of around one minute and, in most premises, such a delay is unlikely to be a matter of concern. 

You mention a "normal" background noise level of 44dB.  Is this a measurement taken in a cubicle with the flush going?  Or in a shower with the shower going?

If it's a simple wc it sounds like it complies, and if it's also a shower, it may need a visual warning signal as well. 

Stu

[colin todd]

5839-1 advises that flushing toilets and running showers can be ignored in determining background noise levels.

[Clevelandfire 3]

The human ear can't differentiate 3db.

Incorrect. The human ear can differentiate between 3dB

[David Rooney]

The human ear can't differentiate 3db.

Incorrect. The human ear can differentiate between 3dB

Maybe if you've just had them syringed or your 16 years old and sitting in an anechoic chamber.

If you're middle aged, with ear wax sitting in a factory toilet I doubt you would really conceive the difference.... but your are correct I should have used the technical term "hardly differentiate".

[Phoenix]

5839-1 advises that flushing toilets and running showers can be ignored in determining background noise levels.

Yes, I can't quite get my head round that. 

If you're in a toilet and you've pulled the flush then the noise of the flush doesn't last for long and you're probably in a position to be leaving the room very soon. 

If you're in a shower, with the shower going, the noise of the shower is likely to last a reasonably long period - 5 or 10 minutes in the shower is not unusual - and you are not in a position to readily leave the building on hearing the alarm.  In fact, you're in one of the the worst conditions you can be in whilst awake, you're naked and wet.  You're probably the one person in the building that deserves the earliest warning of fire, not the latest.

What rationale can support ignoring the noise of a shower when assessing audibility levels?

Stu

[JFW]

Thanks for the various comments which confirm my own conclusions.

The toilets in question are off an un-occupied attrium area used as a display area, so it is a quiet area and the nearest sounder is approx 3 meters from the outer toilet door.

Going through the outer door you go into a small corridoor with 2 doors infront of you for the gents and ladies.

The gents is a small room with a single wc with hand basin and hand dryer. The ladies is double the size with 2 wc cubicles and a single hand basin and hand dryer.

My initial conclusion is that even though the sound is below 60 dB, it can clearly be destinguished over the normal background noise and therefore no further action should be required.

I have also concluded that even though the background noise rises when the wc is flushed or the hand dryer is used, as these will last for less than 30 seconds, they can be ignored.

[colin todd]

Phoenix, its called pragmatism and reasonable practicability, in conjunction with the ability of the human ear to differentiate sounds.  The recommendation was included in the BS as a result of an over zealous officer (and one in God's own country you will be surprised to learn) demanding sounders in en suite bathrooms of hotel bedrooms.  One just rejoices that it was not as silly as an officer in a less civilised country that neighbours God's own country asking for emergency lighting fittings in the bathrooms.

Frankly, the clear danger of taking a shower is such that it is no longer the Hitchcock film that causes me to shake with fear when I take a shower, it is the chance of dying from fire.

[Phoenix]

Colin,

I stopped showering some years ago just to be on the safe side.

Stu

[colin todd]

 Stewart, Very wise. Taking a shower puts people at risk from fire-its official cos firemen want all sort of fire precautions in showers. It reminds me of the Factory Mututal insurance surveyors who always insist on sprinkler protection of water cooling towers.

[Phoenix]

I heard of a sprinkler system in a swimming pool.  Ok round the edges maybe but over the pool itself!!?  I can't help chuckling when I think of it.  They had to be taken out because of corrosion due to chlorine fumes.

Stu

[colin todd]

I seem to remember Winchester swimming pool burning down though. My recollection is that there was some delay in sending the full PDA because there was reliance on an auto dialler to call the fire brigade.

[Davo]

Stu

Dependent on the enclosure size and construction, power, water pressure etc etc a shower can reach over 70dB at 1m


davo

[colin todd]

And what proportion of the 70dB is centered around a frequency of 1kHz?