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Frequently Asked Questions
Frequently Asked Questions
1. What is
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.
2. Where does
CO come
It 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.
Frequently Asked Questions
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.
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.
3. What are the
of CO
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 table on page 4 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.
Frequently Asked Questions
Effects of Cumulative CO Exposure
CO Parts per Million
Inhalation Time (approx.)
& Symptoms Developed
The maximum allowable
concentration for continuous
exposure in any 8 hr period
according to Occupation Safety &
Health Association
Slight headache after 11/2 hrs
Slight headache, fatigue, dizziness,
nausea after 2-3 hrs
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
Dizziness, nausea and convulsions
within 45 minutes. Unconsciousness
within 2 hrs. Death within 2-3 hrs
Headache, dizziness and nausea
within 20 minutes. Death within 1 hr
Headache, dizziness and nausea
within 5-10 minutes. Death within
25-30 minutes
Headache, dizziness and nausea
within 1-2 minutes. Death within 10-15
Death within 1-3 minutes
Frequently Asked Questions
4. How big is
the problem
of CO
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.
Frequently Asked Questions
• 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
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.
6. Why do I
need a CO
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.
7. I have no gas
appliance in
my house - do
I need a CO
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.
8. How does the
Ei range of
CO alarms
There are different types of CO sensors which, because they work
in different ways, have different characteristics. All 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.
Frequently Asked Questions
9. Where should a
CO alarm be
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
10. How many CO
alarms should I
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.
Frequently Asked Questions
11. Why does the
time for the
horn to come
on depend
on the
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.
12. How do
Ei CO Alarms
to BS EN
50291 give
When the CO Alarm detects potentially dangerous levels of CO,
a red light on the cover will flash. The alarm will sound if the CO
levels persist, or rise. The table below shows how the alarm reacts
to different levels of CO and exposure.
CO level in ppm
Red alarm light
1 flash every 2
2 flashes every
4 flashes every
Sounder operates
Within 60 to 90 mins
Within 10 to 40 mins
Within 3 mins
The Ei261DENRC will indicate the ppm CO detected (above
50ppm) on the digital display on the front panel of the alarm cover.
13. Can the
alarms be
The Ei Professional model Ei261ENRC and Ei261DENRC (mains
operated with Rechargeable Lithium cells) can be
interconnected to other Ei261ENRC and Ei261DENRC units so
that when one senses CO, they will all alarm. Twelve units may
be interconnected, but only the unit sensing CO will have its red
light lit in order to identify the area in which CO was detected.
We would recommend that when more than one CO alarm is
installed in a property they should be interconnected.
14. Can I signal
to other
devices from
a CO alarm?
Yes, either an Ei261ENRC or Ei261DENRC can be used with a
remote relay model Ei128RBU (with Ei128COV cover), which is
rated at 5 Amps. The relay can be used to switch shut off
valves, sounders or strobes, or signal to other suitable remote
devices as required. The relay has an optional pulse feature,
which is suitable for signalling to Warden Call Systems widely
used in Sheltered Housing Schemes.
Frequently Asked Questions
15. Can I
CO alarms to
a smoke alarm
There is merit in interconnecting CO and smoke/heat alarm
systems, as it will improve audibility throughout the property
However, it is generally considered that interconnecting CO
alarms into a smoke/heat alarm system is not good practice, as
the actions that should be taken in the different emergencies
are quite unique:
• If a fire occurs, you should keep doors and windows closed to
contain the fire as much as possible.
• If a CO leak occurs, you should open all doors and windows
to ventilate the area as much as possible - at the same time
turning off the appliance/s from where CO leak is being
We believe that interconnection between the 2 types of systems
may be considered if the user is able to determine which of the
alarms has caused the system to operate (the smoke alarm or
the CO alarm) so enabling them to make the correct decision
on what action should be taken. The only foolproof method of
achieving this is by having a means of silencing the remaining
system i.e the alarms not actually sensing smoke or CO. The
solution to this problem would be the addition of an Ei1529RC
Alarm Control Switch into the system.
If any of the alarms in the system operate (CO, smoke or heat) it
is only necessary to press ‘Locate’ on the Ei1529RC switch. This
will silence all alarms that are not actually sensing either CO,
smoke or heat, enabling the user to quickly and easily identify
which of the alarms is sounding. This gives complete control over
the system allowing the occupant to take the safest action
according to the problem identified. Additionally, if found to be
a false alarm, simply press 'Hush’ on the control switch to silence
the alarm. The entire alarm system can also be tested regularly
by pressing the ‘Test’ switch.
The Ei261ENRC and the Ei261DENRC CO alarms have an
interconnect feature that allows them to be interconnected
with any of the Ei160RC series smoke and heat alarms (Not
RadioLINK models). Adding the Ei1529RC switch is a simple job,
only requiring a 3 core connection from the alarm (smoke,heat
or CO) closest to where the Ei1529RC switch is to be installed.
16. Do they meet
the standards?
All Ei CO alarms comply with BS EN50291: 2001 and they are
Kitemarked to show that they have been third party tested to
this standard.
Frequently Asked Questions
17. Do the CO
alarms have
The mains operated models Ei261ENRC and Ei261DENRC are
supplied complete with sealed-in tamper proof Rechargeable
Vanadium Pentoxide Lithium standby cells, designed to last at
least 10 years without the need for replacement and can power
the unit for a minimum of 30 days in the event of mains failure.
The battery is monitored, and if it starts to become depleted
(i.e. with mains off), or if it becomes defective, the unit beeps
every 40 seconds.
18. Are the mains
Ei261ENRC and
easy to fit?
Yes, these models are supplied with an `Easi-fit` surface
mounting plate, with integral terminal block and cable cover.
The terminal block is permanently fitted to the mounting plate.
The built-in battery connects as the unit is slid on to the plate.
Conduit (up to 25 x 16mm) can be attached to the top or
bottom of the unit for surface wiring. The units can be ceiling or
wall mounted.
19. Will I get
Every effort has been made to make the unit insensitive to
normal household chemicals. However, units may go into alarm
if cigarette smoke is deliberately blown into the unit, or if
aerosols, paints or similar materials are used nearby. All Ei CO
alarms are fitted with a manual test/hush button which, when
pressed, will silence low levels of CO gas for approximately 5
minutes. The unit will then automatically re-set to standby mode.
For safety reasons the hush feature cannot over-ride an alarm
caused by dangerously high levels of CO.
20. How often
should they
be tested,
and do they
have to be
The CO alarm should be tested weekly by pressing the test button.
The alarm may be cleaned externally with the narrow nozzle of a
vacuum cleaner and wiped down with a damp cloth (disconnect
the mains on Ei261ENRC/Ei261DENRC/Ei225EN models). The sensor
may be tested annually in CO gas to ensure that it is fully
operational. To simplify this process, all Ei CO alarms have a “quick
test” feature. Pressing the test button causes the unit to sample for
CO every 4 seconds so that when CO gas is injected into the sensor
it will respond almost immediately with 3 short beeps. The alarm will
automatically re-set to standby within 3 minutes. Apart from sensor
replacement after 5 years (Ei261ENRC and Ei261DENRC only) no
other servicing is required (see 22 below).
21. How will I know
if it is my CO
alarm or my
smoke alarm?
The Ei range of CO alarms have a distinctive on-off sound of 3 pulses,
followed by a pause, as compared with a typical smoke alarm which
has a rapid pulsing sound. In addition, when the CO alarm is
detecting CO, the red light in the centre of the cover will flash.
Frequently Asked Questions
22. How long
does the unit
The CO alarms are sophisticated electronic devices with many parts,
including the sensors, and will not last indefinitely. We recommend
that the Ei205ENA and Ei225EN models should be replaced after 5
years in operation. The mains operated models Ei261ENRC and
Ei261DENRC are designed to last 10 years and have a replaceable
sensor module, which we recommend be replaced after 5 years use.
This simply requires the pulling out of the sensor module from the rear
of the alarm and replacing with a new sensor module (Ei261MEN)
readily available at a modest cost.
23. What should I
do when the
alarm goes
24. How much
electricity does
a mains
operated CO
alarm use?
The Ei261ENRC/Ei261DENRC/Ei225EN models use only one unit of
electricity per week.
25.Will it detect
other gases?
The Ei CO alarm is precisely calibrated so that it will only detect CO
gas. IT WILL NOT detect the presence of natural gas (methane),
propane, butane or other combustible gases/fuels. Therefore, a
detector specific to the other gas, or gases, that may be present
must be used in addition to the CO detector, as required.
26.Can I use it
instead of a
smoke alarm?
No! CO alarms are not suitable as early warning fire alarms.
Fire produces CO, however the measured response of the CO alarm
could allow a fire to get out of control before it warned of danger.
Smoke alarms must be fitted for protection against fire.
27.Why are CO
alarms more
than smoke
The technology used in Ei CO alarms is much more complex and
sophisticated than smoke alarm technology. Cheaper less
sophisticated CO alarms are available, but they may not be as
reliable and are commonly prone to false alarm.
Open the doors and windows to ventilate the area.
Stop using the appliance; turn it off if possible.
Evacuate the property leaving the doors and windows open.
Ring your gas or other fuel supplier on their emergency number;
keep the number in a prominent place.
• Do not re-enter the property until the alarm has stopped.
• Get medical help immediately for anyone suffering the effects of
CO poisoning (headache, nausea) and advise that CO poisoning
is suspected.
• Do not use the appliance again until it has been checked by an
expert; in the case of gas appliances this must be a CORGI
registered installer.
Frequently Asked Questions
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