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Frequently Asked Questions about the Carbon Monoxide Alarms from Aico, part 1

  2009-06-30         admin         Safety » Fire Safety
We have all heard about the Carbon Monoxide Alarms, and most of us still have some questions related to either What are the CO alarms/how do they function/do we really need them/how is CO produced, etc. For those of us who don't fully know everything about the Carbon Monoxide Alarms, below is an Aico Guide to the Frequently Asked Questions about the Carbon Monoxide Alarms (download the Aico pdf, or view the entire FAQ here and on In this first part you can read about the
  1. What is Carbon Monoxide?
  2. Where does CO come from?
  3. What are the symptoms of CO poisoning?
  4. How big is the problem of CO poisoning?
  5. How can I protect myself and my family from CO?
  6. Why do I need a CO alarm?
  7. I have no gas burning appliance in my house - do I need a CO alarm?
  8. How does the Aico Ei range of CO alarms work?
  9. Where should a CO alarm be sited?
  10. How many CO alarms should I fit?
  11. Why does the time for the horn to come on depend on the concentration of CO?
Question 1. What is Carbon Monoxide?
Carbon Monoxide (CO) is an invisible, odourless, tasteless and extremely toxic gas. It is absorbed by red blood cells in the lungs in preference to Oxygen - this results in rapid damage to the heart and brain from Oxygen starvation.
Question 2. Where does CO come from?
Carbon Monoxide is produced by appliances or vehicles powered by any fuel such as coal, oil, natural and bottled gas, paraffin, wood, petrol, diesel, charcoal, etc. Normally it is vented out of a building through chimneys or flues. There are a variety of situations which can arise which may lead to CO filtering into the home instead of being vented into the outside atmosphere:
  • A cracked heat exchanger on the gas central heating system This is a particularly dangerous source of CO, as leakage often tends to be very heavy. This problem can arise as a result of consumers not getting their appliance serviced every year and, in some cases, improper maintenance and servicing by the contractor hired to do the job. Disconnected, cracked, rusted or corroded flue pipe or vent In the UK, this is an area of great importance. Even in those homes that do have their central heating checked annually, flues and vents may not be adequately checked. If a flue cracks, CO will leak into the home. Many recent cases of CO poisoning have been as a result of poorly installed flues.
  • Blocked chimney, vent or flue This is an area of crucial concern as inadequate ventilation is the main cause of Oxygen starvation, increasing the levels of CO. It is a subject that has been researched by the Gas Consumers Council (GCC), now Energy Watch. Two million complaints were recorded over a five year period and it was the most common gas consumer complaint. Research reveals that poor construction, quality control standards and ignorance are to blame.
  • Improper appliance installation Instances of this have occurred recently; improper appliance installation resulted in a fatality and,when investigated, it was revealed that the Council concerned had used the same contractor to fit over 2,000 of the same gas units, all of which were subsequently found to have been incorrectly installed.
  • Reverse stacking Any of the above problems with appliances may result in the occurrence of reverse stacking. This arises with appliances which distribute air through air ducts into all parts of the home. If the ventilation process is inhibited for whatever reason, when the appliance draws in air to burn gas, CO will also be drawn in, resulting in it being circulated through air ducts to all parts of the home.
  • Backdrafting With an increase in the number of devices which extract the air from the home, e.g. bathroom extractor fans and kitchen vents, in conjunction with the more energy efficient homes, a negative pressure situation may occur within a home. This results in a reverse in the airflow spilling CO into the living area. The severity of CO emissions in the home will often be exacerbated in new energy efficient homes, particularly where double glazing has been installed. This removes the draughts so often associated with older properties where a natural ventilation system existed.
  • Appliances without flues Some appliances do not have flues, for example gas cookers. These can cause CO poisoning particularly if used for long periods e.g. to heat a room.
Question 3. What are the symptoms of CO poisoning?
Heavy doses of CO will cause a person to collapse and die within minutes. Lesser doses can cause headaches, drowsiness, fatigue, nausea, vomiting and flu like symptoms. The symptoms of poisoning vary depending on the level of absorption by the human body. While most people are aware that high levels of CO are harmful, it is less well known that the length of exposure is also important. A relatively low level of CO for a long period can cause the same symptoms as a high level of CO for a short period. The list below shows the concentration of CO measured in parts per million and the time taken for symptoms to develop. A major problem is that the symptoms of CO poisoning - headaches, dizziness, nausea - can easily be confused with other illnesses, particularly colds or flu. Consequently, the medical profession is often not able to readily identify the true cause of the problem until it’s too late.

Effects of Cumulative CO Exposure

CO Parts per Million (ppm) / Inhalation Time (approx.) & Symptoms Developed
  • 35ppm - The maximum allowable concentration for continuous exposure in any 8 hr period according to Occupation Safety & Health Association
  • 150ppm - Slight headache after 11/2 hrs
  • 200ppm - Slight headache, fatigue, dizziness, nausea after 2-3 hrs
  • 400ppm - Frontal headache within 1-2 hrs, life threatening after 3 hrs, also maximum ppm in flue gas (on air free basis) according to US Environmental Protection Agency
  • 800ppm - Dizziness, nausea and convulsions within 45 minutes. Unconsciousness within 2 hrs. Death within 2-3 hrs
  • 1,600ppm - Headache, dizziness and nausea within 20 minutes. Death within 1 hr
  • 3,200ppm - Headache, dizziness and nausea within 5-10 minutes. Death within 25-30 minutes
  • 6,400ppm - Headache, dizziness and nausea within 1-2 minutes. Death within 10-15 minutes
  • 12,800ppm - Death within 1-3 minutes
Question 4. How big is the problem of CO poisoning?
It is a regrettable situation that the number of people killed or injured by accidental CO poisoning is unknown. Hospitals stopped recording incidents some time ago, but the last estimate was 200 deaths per year, with an unknown number of non-fatal occurrences.

Research undertaken in 1994 in a sample of 250 homes, showed that 10% of households had a higher level of CO than would normally be expected. On a national scale, this could mean that as many as 2 million homes have CO levels higher than the minimum safe level. More recent research, January 2006 by UCL, found that 18% of the homes surveyed had CO levels that exceeded the World Health Organisation guidelines.

Another interesting point revealed in research was that over half of all the people interviewed thought that CO had a smell, which would be quickly recognised and alert the residents that there was a danger present in the home. Also, the residents of over 35% of the homes visited admitted that they had not had appliances serviced in 3 years. After the above findings, it was decided to carry out further research by interviewing doctors to give their likely diagnosis of patients presenting symptoms of headaches, dizziness and nausea. It was interesting to learn that many possible diagnoses were given but not one doctor interviewed, suggested CO poisoning.

When the doctors were asked, in the event of a patient persistently complaining of the above symptoms, would a carboxyhaemoglobin test be carried out, nearly all of the doctors said “No” and most of them being questioned were unsure at what level of carboxyhaemoglobin flu like symptoms start to occur.

The most recent activity regarding CO safety has been the publication of a report by the House of Commons All Party Parliamentary Gas Safety Group in September 2006. The report titled “Shouting about a silent killer, Raising carbon monoxide awareness” has raised serious questions concerning the dangers of CO poisoning in the home. Excerpts from the report:

  • Too many people continue to be harmed or even killed as a result of this entirely preventable problem.
  • One death from CO poisoning is one too many.
  • Improving CO detection by emergency workers and increasing the number of reliable CO detectors in the home is key to the fight to tackle CO poisoning incidents.
  • Every home should have a CO detector with an audible alarm.
  • We call on mortgage and insurance companies to investigate whether requiring all homes to have such an alarm should be part of granting a mortgage or insurance cover.
  • The HSE has an important role to play. We press the HSE to introduce a zero-fatality target on CO poisoning.
  • Stacy Rogers (Dominic Rogers Trust) proposed that CO alarms should be a mandatory requirement for all rented accommodation.
Question 5. How can I protect myself and my family from CO?
Install CO detectors and test regularly to make all family members familiar with their distinctive sound. Make everyone aware of the symptoms of CO poisoning. Have all appliances serviced regularly, ensure that air vents are not blocked.
Question 6. Why do I need a CO alarm?
Many people are killed each year, and many more suffer ill health from CO poisoning. If the CO is not correctly vented due to a leaking or blocked chimney or a faulty heating appliance, dangerous levels of CO can build up inside the home instead of being vented outside. People are most vulnerable whilst asleep or nodding off by their fireside.
Question 7. I have no gas burning appliance in my house - do I need a CO alarm?
Gas appliances, although a major risk if not maintained properly or given adequate ventilation, are not the only source of CO. Other appliances burning solid fuel, bottled gas, paraffin, wood, petrol, diesel, charcoal etc. also produce CO gas.
Question 8. How does the Aico Ei range of CO alarms work?
There are different types of CO sensors which, because they work in different ways, have different characteristics. All Aico Ei CO alarms use a new generation proven electrochemical cell type sensor. This sensor type has a low power requirement well suited for use in a battery powered alarm in order to avoid frequent battery replacement. The electrochemical sensor works by catalytic action in direct proportion to the amount of CO present. It has a minimum 5 year life expectancy with good immunity to contaminant gases.
Question 9. Where should a CO alarm be sited?
The BS EN 50292 Code of Practice (COP),which is a guide to selection, installation, use and maintenance of CO alarms, states “it is not possible to give specific guidance on the exact location of a CO detector”. However, it does say that, where the CO alarm is located in the same room as the apparatus, if the CO alarm is mounted on the ceiling (our preferred position) it should be at least 300mm from any wall. We would add the recommendation that there should also be 300mm between the CO alarm and any other form of obstruction e.g. a light fitting. The COP goes on to say that if the CO alarm is mounted on the wall, it should be at least 150mm from the ceiling, but above the height of any door or window. Whether ceiling or wall mounting, the CO alarm should be between 1m and 3m (measured horizontally) from the potential source of CO.

The CO alarm should not be installed:

  • In an enclosed space e.g. a cupboard
  • Where it can be obstructed e.g. by furniture
  • Directly above a sink
  • Next to a door, window, extractor fan, air vent or similar ventilation openings
  • Where the temperature may drop below - 5ºC or exceed 40ºC
Question 10. How many CO alarms should I fit?
The BS EN 50292 guide recommends that, ideally, you should have a detector in every room that contains a fuel burning appliance. However, if you have more than one appliance, but only one detector, you should consider the following priority areas when deciding where best to put the detector: rooms containing a flue-less or open-flued appliance; rooms where the occupants spend most time; rooms in which the appliance is most used. The guide further suggests that you should consider fitting CO alarms, or repeaters in other areas where there is no appliance but the occupants spend considerable time and may not hear an alarm sited elsewhere in the property. These areas could include sitting rooms and bedrooms. In these areas wall mounting at normal breathing height is suggested as the more appropriate siting position.
Question 11. Why does the time for the horn to come on depend on the concentration of CO?
The micro-chip in the unit calculates the toxic level of CO gas/exposure time in a similar way to the human body. Warnings are given for both high CO levels for short periods, and lower CO levels for longer periods. It will ignore brief exposures which do not have any harmful effect.

Read the second part of this CO Q&A (read all the FAQ, or download the pdf guide from Aico) to find out more about the next set of questions related to the Carbon Monoxide Alarms(buy Aico CO alarms online):

12. How do Ei CO Alarms conforming to BS EN 50291 give warning? 13. Can the alarms be interconnected? 14. Can I signal to other devices from a CO alarm? 15. Can I interconnect CO alarms to a smoke alarm system? 16. Do they meet the standards? 17. Do the CO alarms have back-up power? 18. Are the mains operated models Ei261ENRC and Ei261DENRC easy to fit? 19. Will I get false/nuisance alarms? 20. How often should they be tested, and do they have to be serviced? 21. How will I know if it is my CO alarm or my smoke alarm? 22. How long does the unit last? 23. What should I do when the alarm goes off? 24. How much electricity does a mains operated CO alarm use? 25. Will it detect other gases? 26. Can I use it instead of a smoke alarm? 27. Why are CO alarms more expensive than smoke alarms?