EICR , smoke alarms and rented flats

[tabbypurr]

which indicates that they've stopped taking the system's (many false) alarms seriously.

[ARW]

They all came downstairs, saw me and just assumed that I had set the alarm off.

[Peter Parry]

Neither fixed point trigger nor rate of rise heat alarms are adequate for protecting occupants from common causes of fire. They belong only in kitchens, utility rooms and garages where fires are likely to start quickly and other detectors cannot be used. Rate of rise detectors can also suffer nuisance alarms if for example they are positioned above oven doors where the out rush of hot air when the oven door is opened can cause them to trigger.

Neither optical nor ionisation detectors detect fires. Both detect products of combustion. Quite often victims of fires are found away from the source of the fire. Very few people burn to death, the fumes (Carbon Monoxide in particular) kill them first and the influence of heat is of minor importance.

Heat alarms trigger at about 60 deg C (fixed point) or for rate of rise detectors by about 8 deg C per minute rise. Neither are useful for life protection in common areas because by the time the fire is sufficiently developed to trigger temperature alarms it will already be producing lethal levels of fumes. Hence their only use is in small confined areas such as kitchens where fires are likely to start and either ionisation or optical alarms will routinely produce unacceptable numbers of nuisance alarms or become compromised over time by atmospheric contamination.

Positioning is important but unless a kitchen is only used to warm food and nothing will ever get burned an ionisation alarm is wholly unsuitable in a kitchen no matter where it is installed. In a normal two story construction the critical sensor is the one placed on the ceiling at the top of the stairs. That will trigger first in about

80-90% of cases no matter where the fire starts. Even quite badly placed alarms will work in most cases, just not as quickly as they could.

Unfortunately fire protection by combustion detectors is one of the fields where too many people believe that more = better and fail to understand that if there are too many (and too many is a small number) nuisance alarms then occupants will both ignore and later disable the alarms. "I've put lots of sensors in so its much safer" often really means "I've put lots of sensors in so its much less safe but I've created a really good illusion of safety".

[Robin]

I agree with the message in the para. above. but wonder if some might take it as an argument against multiple detectors per se. Eg I took the view that smoke detectors were best placed in the usual circulation spaces which here gave 3 (above stairs, rear landing and downstairs gall) and in rooms where electrical kit was routinely left on and unattended which gave another 3. Most people think that's a lot in a 3 bed terrace house. The more so as 2 are only 2m apart. But there's a closed door between them so I reckoned it was a price worth paying for earlier warnings. And we've had perhaps 3 nuisance alarms in 10+ years

- and that includes those from neighbours' summer barbecues ;)

[tabbypurr]

You and most people are wrong on one point. Ionisation alarms can cover kitchens with no significant false alarms IF positioned correctly. Obviously 'correctly' there means something different than for other alarm types or in other locations.

NT

[ARW]

That goes against the advice from every manufacturer.

[Robin]

Do you do much cooking?

[tabbypurr]

It certainly works well. Commercial installers of course want to stick something in & forget it, and that's who such advice is aimed at. But an ionisation alarm needs moving until it no longer false alarms. And since the kitchen is the prime fire risk area, I'd rather have it ionised than heated.

NT

[Robin]

On 25/11/2018 18:18, [e-mail] wrote: <snip>

And your authority for that is?

Cf:

"Ionisation smoke alarms have traditionally been used throughout properties for many years. Designed to react quickly to fast flaming fires, ionisation smoke alarms are most sensitive to small particles. When fires produce little or no smoke but the fuel is subject to rapid combustion, the ionisation smoke alarm is the quickest to sense its presence. These fires tend to originate from materials such as paper and clothing. "

"Less prone to false alarms than ionisation, optical smoke alarms are slightly quicker at detecting slow smouldering fires that tend to produce a lot of smoke. Also known as photo-electric alarms, this quick response time to smouldering fires is down to the optical smoke alarm's high sensitivity to large particles in the air. The optical sensing chamber effectively "sees" when smoke is present, as the large particles block and cause an infrared light to scatter."

• similar views from others sources

And the main cause of death in domestic fires is smoke inhalation.

[Tim Lamb]

We seem to be going round this again:-)

Slightly sideways and pertinent to why detectors may be disabled..... battery life? Set of 3 linked detectors. Batteries all failed within 2 weeks after about 6 months use! PP3s are not cheap!

[Robin]

Seems a bit odd if they were alkaline.

Anyhow, have you considered NiMH? I've been running linked detectors with NiMH PP3s for the c.8 years since the original Alkaline expired. I've had to replace one or 2 of the NiMHs (from Lidl) but so long as I can manage the ladders every 6 months[1] it's economical.

What I'm dithering over, with the detectors approaching their end of life, are the pros and cons of alkaline battery vs rechargeable lithium. The choice'd be easier if I knew my expiry date but that just shifts it to another decision...

[1] for pre-emptive recharges: something that I don't begrudge after the time it started beeping at 02:00 after a heavy night :)

[ARW]

Lack of mains power?

I would expect 5 years for a normal mains powered with battery back up smoke detector before the battery goes flat.

PP3s are about a quid unless you buy them at a petrol station.

[Tim Lamb]

I didn't install them! Trip is on at consumer unit.

That's more like it.

Huh. Tell Tesco.

>

[spuorgelgoog]

Exactly a quid from a quid shop, but I'm not sure I'd trust my life to them.

Messrs CPC's GP High Power Alkaline are £9.51/10

Ultralife Lithium Manganese 10 year shelf life are £6.75 *each*

Plus the VAT, of course.

Owain

[Dave Liquorice]

Wrong type of detector?

s/false/nuisance/

And a great many people don't realise that you don't have very long before a fire becomes "interesting" to escape from or simply unsurviveable. Fire engines don't have "Get out, stay out, get us out" for no reason.

[Bob Eager]

Given that they do Duracell Industrial ones for £9.95/10 (as above, plus VAT), I think I'd go for those. The GP ones are OK, but the Duracells seem a lot better.

(that price is to be found in most of their 'brochures', including the Bulk Bargains one. Find these online if CPC don't send them to you. The part number is the same but with a time limited two digit suffix.

[John Rumm]

+1, I have never been that impressed with GP batteries.

Yup, there is normally a special offer available on batteries...

[Terry Casey]

Kodak alkaline from Poundland - 10 year shelf life.

[Peter Parry]

Well I have come across a battery powered ionisation alarm originally positioned just outside a kitchen door which had been relocated by the occupant to a bread bin inside the kitchen to shut it up but that oddity aside neither optical nor ionisation alarms are suitable for kitchens no matter how much fiddling with position to find pockets of unmoving air one does.

Current guidance is in BS 5588 11990, Fire precautions in the design, construction and use of buildings. BS EN 14604 covers Smoke alarm devices.

A simple summary is (in England and Wales) Building Regulations Document B (Volume 1).

Building Regulations Document B requires a minimum of Grade D Category LD3 ? Mains powered interlinked alarms with an integral back-up power supply.

This covers new builds, materially altered dwellings, loft conversations and certain building extensions for standard dwellings.

All dwellings should be provided with an alarm system to at least Grade D, Category LD3 means the installation of mains powered alarms with an integral back-up power supply within the escape routes of the property (i.e. hallways and landings). In addition, the Regulations require a heat alarm to be installed in any kitchen areas where the kitchen is not separated from the circulation space or stairway by a door.

Approved Document B (Fire safety) ? Volume 1: Dwelling houses (2006 edition incorporating the 2010 and 2013 amendments) is the simplest summary (and free) at

This requires " Positioning of smoke and heat alarms

1.10 Detailed guidance on the design and installation of fire detection and alarm systems in dwelling houses is given in BS 5839-6:2004. However, the following guidance is appropriate to most common situations. 1.11 Smoke alarms should normally be positioned in the circulation spaces between sleeping spaces and places where fires are most likely to start (e.g. kitchens and living rooms) to pick up smoke in the early stages of a fire. 1.12 There should be at least one smoke alarm on every storey of a dwellinghouse. 1.13 Where the kitchen area is not separated from the stairway or circulation space by a door, there should be a compatible interlinked heat detector or heat alarm in the kitchen, in addition to whatever smoke alarms are needed in the circulation space(s)."

The use of optical or ionisation detectors in kitchens is deprecated.

[Peter Parry]

Standard NiMH have quite a high self discharge rate, about 1-4% per day and very dependent upon temperature. Low discharge batteries such as Eneloop claim to be much better retaining 60% of charge for one year. I'd still not use them for alarms where the standby current is negligible. The life of a battery in a smoke alarm is effectively its shelf life as so little current is used.

The most appropriate battery now is the non-rechargeable Lithium primary cell and increasingly alarm manufacturers are fitting these as sealed non replaceable units in alarms. When the battery is dead the sensor is also at the end of its useful life (usually 10 years) due to atmospheric contamination/debris and the whole unit is replaced.