Everyone hates it when a smoke alarm goes off for the wrong reason. We know this as a false alarm. False alarms are a real headache for a homeowner or resident, but they are even worse for a landlord as they can be costly, involving a visit to the property by a heating engineer or electrician.

CO alarms are very different from smoke alarms, and false alarms are very unlikely. They do not alarm when the toast is burnt or when someone抯 had a steamy shower. When a CO alarm indicates the presence of CO it must not be ignored.

Ei Electronics ?Aico抯 parent company and manufacturer of the Ei Professional range of smoke and CO alarms has recently seen a few worrying incidents where complaints were made about CO alarm false alarms, when the alarms where actually working very well indeed. The outcomes could base been very different.

Case studies

In the first instance, a woman who had purchased and fitted another manufacturer抯 CO alarm was rightly concerned when it went into alarm. She called out her gas supplier who checked the boiler, found nothing wrong and said the CO alarm must be faulty. The woman rang the manufacturer who said that it may have come from a faulty batch and sent her a replacement alarm. The alarm went off again; she repeated the process with the same result. This, in fact, happened four times.

Whilst waiting for another replacement alarm to arrive, the women decided it was best to be on the safe side and purchased another manufacturer抯 CO alarm ?Ei. The Ei CO alarm went into alarm at which point she rang Si who sent her an Ei2O6DEN CO alarm which has a built in digital read out feature. The alarm showed 80ppm of CO in her kitchen; however, she measured 165ppm in the corridor outside her flat. It transpired that the CO was coming from the flat below her ?and no less deadly for it.

The other incident is from a housing association. Ei recently received two Ei26IENRCs CO alarms which were reported as false alarming. Ei put the returned alarms through their paces to find they were performing accurately. We immediately advised the

housing association that the alarms are working and that therefore CO must be present in the properties from which they were taken. The housing association was taken aback and started an immediate investigation into the source of the teak.

Approach with caution

The lesson from those two stories is to approach claims of æ…ºalse?alarms from CO alarms carefully. Unlike smoke alarms where dust, cooking fumes, etc. can cause false alarms, the same problem does not exist with CO alarms.

That is because CO alarms work very differently from smoke alarms. When CO is present, it enters the sensor through a gas diffusion hole. A graphite filter prevents any external contaminants from entering. A platinum sensing electrode then catalyses the oxidation of the CO. Combined with the water present in the electrolyte, this reaction causes the voltage rise and consequently, small current flows between the two electrodes. This output is directly proportionate to the amount of CO gas present. The microchip in the unit then activates the LED/horn/display to give a warning applicable to the CO level sensed.

As you can see, it抯 a complicated process, which is why CO alarms are considerably more expensive than smoke alarms and also why they very rarely go into false alarm. In fart, the only reason for them to false alarm is not from external contamination, but if there is something wrong with the alarm itself. If you get a good quality CO alarm front a reputable manufacturer ?avoiding the cheap influx from the Far East which has been blighted with problems and product recalls梩hen this should never be a problem.

For added reassurance, install a CO alarm that provides more information than simply an alarm warning. The Ei261ENRC, for example, features high and low level LED indicators, with a special pre alarm LED indication for detection of CO at 50ppm. When the levels detected reach dangerous levels, a red warning LED combines with an integral built in sounder outputting 85Db(A) at 3m to provide a full audio-visual warning. Others indicators confirm mains power supply and fault indication. The alarm also comes with a memory feature which enables the user to tell if CO has been detected during a period of absence.

On the agenda

There is no legal requirement to fit a CO alarm at present, although two sears ago the House of Commons All Party Parliamentary Gas Safety Group called upon mortgage providers and insurance companies to make the installation of a 憆eliable CO detector?a prerequisite for agreeing a mortgage or providing home insurance. This indicates CO poisoning is on the political agenda.

A landlord is, of course, required by law to check all gas appliances by an approved engineer every 12 months. But this is not nearly adequate protection as things can and do go wrong between inspections and, what抯 more, CO is given off as a by-product of virtually any combustion process; any household appliance that burns coal, oil, bottled gas, paraffin, wood, petrol or diesel or charcoal can be a potential source of CO. Let抯 not forget, CO is an extremely dangerous ?lethal ?gas. You can抰 smell it, see it and you certainly can抰 hear it. Most victims die in their sleep from a strong leak ?some in just minutes. The only way to detect it is by fitting a good quality CO alarm.