در مورد سنسورهای مونوکسید کربن (استاندارد BS EN 50291:2001)

Electrical apparatus for the detection of carbon monoxide in domestic premises — Test methods and performance requirements

Foreword

This European Standard has been prepared by the Technical Committee CENELEC TC 216, Gas detectors.
The text of the draft was submitted to the formal vote and was approved by CENELEC as EN 50291 on 2000-08-01.
The following dates were fixed:
– latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2002-02-01
– latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 2006-04-01

Annexes designated “normative” are part of the body of the standard. Annexes designated “informative” are given for information only. In this standard, annexes A and B are informative

Scope

This European Standard specifies general requirements for the construction, testing and performance of electrically operated carbon monoxide gas detection apparatus, designed for continuous operation in domestic premises. The apparatus may be mains or battery powered. Such apparatus is intended to warn of an accumulation of CO, enabling the occupant to react before being exposed to significant risk

:This standard specifies two types of apparatus, these are
Type A – to provide a visual and audible alarm and an executive action in the form of an output signal that can be used to actuate directly or indirectly a ventilation or other ancillary device

Type B – to provide a visual and audible alarm only

:This standard excludes apparatus
for the detection of combustible gases, other than carbon monoxide itself; (see EN 50194:2000)
for the detection of CO in industrial installations or commercial premises; (see EN 45544 series)
for use in boats, caravans or mobile homes
(for CO measurement for smoke and fire detection (see prEN 12239

Normative references

This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies.

EN 50270 – 1999 – Electromagnetic compatibility – Electrical apparatus for the detection and measurement of combustible gases, toxic gases or oxygen

EN 50292- 2001 – Electrical apparatus for the detection of carbon monoxide in domestic premises Guide on the selection, installation, use and maintenanc

EN 60335-1 – 1994 – Safety of household and similar electrical appliances Part 1: General requirements (IEC 60335-1:1991, mod.)

EN 60529 – 1991 – Degrees of protection provided by enclosures (IP code) (IEC 60529:1989)

EN 60704-1 – 1997 – Household and similar electrical appliances – Test code for the determination of airborne acoustical noise Part 1: General requirements (IEC 60407-1:1997)

Definitions

For the purposes of this European Standard the following definitions apply:

۳٫۱ ambient air
the normal atmosphere surrounding the apparatus

۳٫۲ clean air
air which is free of carbon monoxide, interfering and contaminating substances

۳٫۳ domestic premises
any house or building being a place of residence or home of a household, family or person

۳٫۴ fixed installation
an apparatus which is intended to have all parts except replaceable batteries permanently installed

۳٫۵ latching alarm
an alarm which, once activated, requires deliberate action for resetting

۳٫۶ sensor
an assembly in which the sensing element is housed and which
may contain associated circuit components

۳٫۷ sensing element
a device, the output of which will change in the presence of carbon monoxide

۳٫۸ (volume ratio (V/V
ratio of the volume of a component to the volume of the gas mixture

۳٫۹ output signal
a signal characterised by a standby and an activation state by which action may be initiated, e.g. triggering a ventilation device

۳٫۱۰ warm-up time
the time interval between the time when the apparatus is switched on and the time when the apparatus is fully operational

۳٫۱۱ alarm set point
a fixed setting of the apparatus that determines the volume ratio and duration of exposure at which the apparatus will automatically initiate an alarm and, for type A apparatus an output signal

۳٫۱۲ fault signal
a visual and/or audible signal indicating a faulty or failed apparatus

۳٫۱۳ mains-powered apparatus
an apparatus designed to be powered by the
normal domestic mains electrical supply, with or without an alternative power source

۳٫۱۴ battery-powered apparatus
an apparatus designed to be powered by batteries only

۳٫۱۵ continuous operation
apparatus which is continuously powered with continuous or intermittent automatic sensing

General requirements

General

Unless otherwise stated, the requirements specified are applicable to both type A and type B apparatus.
The apparatus shall reliably detect the presence of carbon monoxide in domestic premises under the stated application conditions, shall produce an alarm, and in the case of Type A apparatus, shall be able to initiate executive actions whenever the conditions (in terms of both level and duration) exceed pre-set alarm set points.
Apparatus which includes functionality additional to carbon monoxide detection shall perform according to the requirements of this standard and to the requirements of any standards relevant to the additional functionality.
The apparatus, electrical assemblies and components shall comply with the requirements of 4.2 to 4.6 and the performance requirements of clause 5. Apparatus shall be designed for continuous operation. The apparatus shall not be class 0 as defined in EN 60335-1.

Construction

The apparatus shall comply with the appropriate requirements of EN 60335-1 as listed in Table 1.

Indicators and alarms

۴٫۳٫۱ Visual indicators shall be fitted and coloured as follows:
a) power supply indicators shall be coloured green;
b) alarm indicators shall be coloured red;
c) where fitted, the visual fault alarm shall be yellow.
The indicators shall be marked to show their function.
The indicators shall be visible when the apparatus is installed in its operating position according to the manufacturers instructions

The apparatus shall have an audible alarm, see 5.3.16.
Alarm indicators and audible alarms shall operate simultaneously at the set points as listed in Table 2.

Once activated, the alarm shall remain in operation at carbon monoxide concentrations above 50 ppm.

All adjustment devices and tools intended for adjustment of, or access to, such adjustment devices shall be designed so as to discourage unauthorised interference with the apparatus.

Fault signals

The apparatus shall provide a fault signal in the event of loss of continuity or short circuit to the sensor.
The fault signal shall be clearly identified and different from a gas alarm.

(Output signal (applicable for type A apparatus only

The apparatus shall provide an output signal at each of the alarm conditions listed in Table 2

Labelling and instructions

۴٫۶٫۱ General All text on the apparatus, its packaging and in the instruction book shall be in accordance with National regulations
.
Labelling
The apparatus shall carry durable label(s) carrying the following information:
a) The manufacturer’s or supplier’s name, trademark or other means of identification;
b) The name of apparatus, model number, if any, and the type of gas to be detected;
c) The number of this European standard;
d) The type of apparatus, A or B;
e) The serial number or manufacturing date code of the apparatus;
f) For mains powered apparatus the electricity supply voltage and frequency and maximum power consumption;
g) For battery powered apparatus the type and size of replacement batteries;
h) Recommendations on the replacement procedures and lifetime of the apparatus.
The markings b) and h) shall be clearly visible with the apparatus in a typical installed position.

The markings shall be legible and shall comply with 7.6 and 7.14 of EN 60335-1:1994.

Cautions
All gas detection apparatus shall carry a caution, on a label attached to the apparatus, for example:
CAUTION: READ THESE INSTRUCTIONS CAREFULLY BEFORE OPERATING OR SERVICING

Instruction booklet
The apparatus shall be provided with an instruction booklet or leaflet. The instruction book or leaflet shall give complete, clear and accurate instructions for the installation, safe and proper operation, and regular checking of the apparatus. It shall include at least the following information:
a) For mains powered apparatus, the correct operating voltage, frequency, fuse-rating (if any) and method of connection to the mains supply system;

b) For battery powered apparatus the type and size of replacement batteries, normal operating life, battery replacement instructions, and information on low battery conditions;
c) Guidance on siting and mounting of the apparatus and the warning that the apparatus should be installed by a competent person, see, EN 50292; d) Actions to take if the apparatus alarms, see EN 50292;
e) An explanation of all warning (visual and audible) and other indicators, including resetting facilities where relevant;
f) A list of commonly occurring materials, vapours or gases, e.g. in cleaning fluids, polishes, paints, cooking operations, etc., which may affect the reliability of the apparatus in the short or long term;
g) Warning of the possible hazards of electric shock or malfunction if the apparatus is tampered with;
h) Instructions on the use of any relevant test procedure supplied with the apparatus;
i) The expected lifetime of the apparatus;
j) For type A apparatus, instructions on the use and characteristics of the output signal;
k) A note stating the working ranges of both temperature and humidity;
l) The alarm conditions;
m) A description of the effects of carbon monoxide on the human body, stating that the apparatus may not prevent the chronic effects of carbon monoxide exposure, and that the apparatus will not fully safeguard individuals at special risk, see annex A of EN 50292;
n) Warning that installation of the apparatus should not be used as a substitute for proper installation, use and maintenance of fuel burning appliances including appropriate ventilation and exhaust systems

The apparatus packaging shall: − Carry a warning that the apparatus should be installed by a competent person; − Carry relevant information regarding storage and transport. The package shall clearly display the following message:

“This apparatus is designed to protect individuals from the acute effects of carbon monoxide exposure. It will not fully safeguard individuals with specific medical conditions. If in doubt consult a medical practitioner“

Test and performance requirements

General requirements for tests

Test samples
:For the purposes of type testing
Compliance with 4.2 and 5.3.15 to 5.3.18 shall be verified using samples as required. These samples should not be used for subsequent tests unless agreed by the manufacturer

Three samples shall be subjected to the tests specified in 5.3.2 to 5.3.13 and for battery powered apparatus, clause 6. All three samples shall pass the test

− Three further samples may be used for the long term stability test 5.3.14 (at the manufacturers discretion). All three samples shall pass the test

۵٫۱٫۲ Preparation of samples
The sample apparatus shall be prepared and mounted when applicable, in accordance with the manufacturer’s instructions without modification.
The entire apparatus shall be subjected to the test conditions.

Use of mask for testing
The use of a mask is allowed for subjecting the apparatus to test gases. The design and operation of the mask used by the testing laboratory, in particular, the gas pressure and velocity inside the mask shall not influence the response of the apparatus or the results obtained. The manufacturer may provide a suitable mask with the apparatus

Test chamber
The construction of the chamber shall be such as to ensure that the apparatus is exposed to a specific volume ratio of test gas in a reproducible manner.

Normal conditions for tests

General
The test conditions specified in 5.2.2 to 5.2.9 shall be used for all tests unless otherwise specified. Before commencing any test sequence, the apparatus shall be allowed to warm-up for a minimum period of 1 h except for 5.3.5

Test gases for alarm testing

The following CO test gas volume ratios shall be used for alarm testing as described in 5.3.1.

Test gases for specified tests
For the long term stability test, 5.3.14, the mixture of CO in air shall have a volume ratio of 10 ppm – ۵ ppm.

For the high volume ratio test, 5.3.6, the mixture of CO in air shall
have a volume ratio of 5 000 ppm – ۱۰۰ ppm

Speed of test gas
The speed of air or test gas in the test chamber shall be between 0,1 m/s and 0,5 m/s. In the case of a mask, the requirements of 5.1.3 apply

Power supply
For mains powered apparatus, the electricity supply shall be within – ۲ % of the nominal value declared by the manufacturer

Temperature
The tests shall be performed using air and test gases of constant temperature – ۲ ”C within the range 15 ”C to 25 ”C throughout the duration of each test

Humidity
The tests shall be performed using air and test gases of constant relative humidity (r.h.) – ۱۰ % r.h. within the range 30 % r.h. to 70 % r.h. throughout the duration of each test

Pressure
The tests shall be performed using air and test gases at ambient pressure – ۲ kPa within the range of 86 kPa to 108 kPa throughout the duration of the test

Removable parts
Optional filters, windshields, or diffusion devices supplied or recommended by the manufacturer shall be attached or removed according to which condition gives the most unfavourable result for the test being conducted

Test methods and performance requirements
General
The apparatus shall comply with all the requirements under the specified test conditions. Unless otherwise stated, each test condition shall be separately varied while the others remain normal as defined in 5.2.

When the apparatus is switched on, a warm-up time during which the apparatus is not in an active monitoring mode, is acceptable.

Whilst the following sequence of tests is recommended the sequence of tests is not mandatory. They shall be carried out in clean air or the test air gas mixture as appropriate.

For all testing of alarm conditions, expose the apparatus sequentially to the following test gases as specified in Table 3 in a step change:
− to clean air for 15 minutes; − to test gas A for 120 minutes or until the alarm activates if less than 120 minutes;
− to clean air for 15 minutes;
− to test gas B for 90 minutes or until the alarm activates if less than 90 minutes;
− to clean air for 15 minutes;
− to test gas C for 40 minutes or until the alarm activates if less than 40 minutes;
− to clean air for 15 minutes;
− to test gas D for 3 minutes or until the alarm activates if less that 3 minutes;
− to clean air for 15 minutes.
The exposure to test gas C and the subsequent exposure to clean air shall only be carried out for the alarm condition test in 5.3.4.

Unpowered storage

Expose the apparatus sequentially to the following conditions:

a) A temperature of (-20 +–۲) °C for 24 h.

b) Ambient temperature for 24 h

c) A temperature of (50 +–۲)º C for 24 h.

d) Ambient temperature for 24 h.

Allow the apparatus to warm up for 1 h and then subject it to the tests given in 5.3.4 to 5.3.13.

۵٫۳٫۳ Output signal

Test

For Type A apparatus, verify, during every test, the state of the output signal according to the manufacturers specification

Performance requirement

The apparatus shall provide the output signal in accordance with the manufacturer’s specification

Alarm conditions

Test

Under the environmental conditions specified in 5.2.5 to 5.2.8, test the alarm conditions as described in 5.3.1

Performance requirement

When exposed to CO – air mixtures, the alarm shall operate according to the conditions in Table 3. Recovery from the alarm state shall take place, after manual resetting if necessary, within 6 minutes when exposed to clean air

Alarm during warm-up time

Test

Mount the apparatus in clean air for 24 h in an unenergized condition. Introduce the test gas D and immediately switch-on

Performance requirements

The apparatus shall alarm within 15 minutes of being switched-on

Response and recovery to a high test gas volume ratio

Test

Expose the apparatus sequentially to the following test gases in step change sequence:

to clean air for 15 minutes

to 5 000 ppm CO as specified in 5.2.3 for 15 minutes

to clean air for 1 hour

to test gas B for 90 minutes or until the alarm activates if less than 90 minutes

to clean air for 15 minutes

Performance requirement

The apparatus shall not alarm during the initial exposure to clean air
The apparatus shall alarm within 3 minutes when exposed to the high CO volume ratio
After the exposure to the high CO volume ratio, the apparatus shall recover from the alarm state within 15 minutes, when exposed to clean air. The apparatus may be manually reset if necessary

The apparatus shall alarm according to the conditions stated in Table 3 for test gas B
After the exposure to test gas B, the apparatus shall recover from the alarm state within 6 minutes, when exposed to clean air. The apparatus may be manually reset if necessary

Temperature effects

Test

Expose the apparatus and the test gas to a temperature of (-10 –۱) ”C for at least 6 h, followed by the ambient temperature for at least 6 h and finally to a temperature of (40 –۱) ”C for at least 6 h. At the end of each exposure interval and before the test conditions are changed, subject the apparatus to the test gas as described in 5.3.1

Performance requirement

Humidity effects

Test

Expose the apparatus and the test gas to a humidity of (30 – ۵) % r.h. at (15 – ۲) C for a period of 6 h followed by an exposure to (90 – ۵) % r.h. at (40 – ۲) C for a period of 6 h. At the end of each exposure interval and before the test conditions are changed, subject the apparatus to the test gas as described in 5.3.1

Performance requirement

Speed of test gas

Test

Expose the apparatus to the test gas A at an air speed of (1,2 – ۰,۱) m/s for 2 hours in a flow chamber with the apparatus in the normally mounted position

Performance requirement

Throughout the test, the alarm shall not operate

Supply voltage variations (mains powered apparatus only)

Test

Set up the apparatus under normal conditions (5.2) at the rated supply voltage Un and frequency. Subject the apparatus to test gas as described in 5.2.2 at a rated supply voltage of Un + 10 % Un . Repeat the test at a supply voltage of Un -10 % Un

Performance requirement

Electromagnetic compatibility

Test

Test the apparatus, including the sensor and interconnecting wiring for electromagnetic compatibility in accordance with EN 50270

Performance requirements

The apparatus shall meet the requirements of EN 50270

Response to mixtures of carbon monoxide and other gases

General

As it is not possible to obtain a stable, ready mixed, test gas mixture as required for this test, Table 4 describes three components which when mixed together in the relative proportions given, will produce a suitable test gas.

Component 1 shall be humidified prior to mixing with components 2 and 3.
NOTE NO and SO2 volume ratios in the resulting test gas may be different from the calculated results because of the reaction between NO, SO2, O2, and water vapour. 5.3.12.2 Test

:Expose the apparatus sequentially to

clean air for 15 minutes

a mixture, the composition of which is described in Table 4, for 90 minutes or until the alarm activates if less than 90 minutes

clean air for 15 minutes

Performance requirement

The apparatus shall not alarm during the initial exposure to clean air
The apparatus shall alarm according to the conditions stated in Table 3 for test gas B
After the exposure to the test gas mixture of composition described in Table 4, the apparatus shall recover from the alarm state within 6 minutes, when exposed to clean air. The apparatus may be manually reset if necessary

Effects of other gases

Test

Subject the apparatus consecutively to the following gas mixtures under the conditions given below

ethanol at a volume ratio of (2 000 – ۲۰۰) ppm for 30 minutes

hexamethyldisiloxane at a volume ratio of (10 –۳) ppm for 40 minutes

The hexamethyldisiloxane test may be carried out with dry gas. After the test in dry gas, allow one hour for the apparatus to reach equilibrium under normal conditions. After exposure to each of these gases, subject the apparatus under normal conditions to the test gases as described in 5.3.1

Performance requirement

The apparatus shall not alarm when exposed to ethanol and hexamethyldisiloxane
When exposed to CO – air mixtures, the alarm shall operate according to the conditions in Table 3. Recovery from the alarm state shall take place, after manual resetting if necessary, within 6 minutes when exposed to clean air

Long term stability

Test

Mount the apparatus, expose it to a CO test gas mixture as specified in 5.2.3. and energize continuously for a period of 3 months. At the commencement of the test and every 30 days thereafter expose the apparatus to the test gases as specified in 5.3.1. During the test, the ambient conditions shall remain within the overall bands specified in 5.2.6, 5.2.7 and 5.2.8 disregarding tolerances

Performance requirement

The apparatus shall not alarm when exposed to the test gas as specified in 5.2.3
When exposed to CO – air mixtures, the alarm shall operate according to the conditions in Table 3. Recovery from the alarm state shall take place, after manual resetting if necessary, within 6 minutes when exposed to clean air

Drop test (applicable to apparatus not intended for fixed installation)

۱ Test

The apparatus shall be dropped from a height of 1 m in each of three mutually perpendicular attitudes onto a concrete floor. Expose the apparatus to test gases as described in 5.3.1

Performance requirements

۵٫۳٫۱۶ Alarm sound level

Test

The test shall be carried out in free-field conditions over reflecting planes, the horizontal plane simulating the floor or the ceiling and the vertical plane simulating the wall
Position the apparatus in accordance with the manufacturers instructions
Position the microphone so that its axis corresponds to the geometric centre of the apparatus, see figure 1

Test in accordance with EN 60704-1
NOTE For apparatus which emit an intermittent or modulated sound it may be necessary to modify the circuit in order to obtain a continuous signal.

Performance requirement

The sound level shall be at least 85 dB (A) at 1 m

Degree of protection

Test

The enclosure of the apparatus shall provide a degree of protection of at least IPX2D

The apparatus shall be tested in accordance with EN 60529, clauses 12, 13 and 14

Performance requirement

The apparatus shall meet the requirements specified in clauses 12, 13 and 14 of EN 60529.

Mechanical strength

Test

The apparatus shall be tested in accordance with the test specified in clause 21 of EN 60335-1 with the following modification to the third paragraph
The apparatus is rigidly supported and three blows are applied to every point of the enclosure that is likely to be weak with an impact energy of (1 – ۰,۲) J

Performance requirement

The apparatus shall meet the requirements specified in clause 21 of EN 60335-1:1994

Self-contained battery powered apparatus

Battery fault warning

General

Self contained apparatus incorporating a battery shall give a visual or audible fault warning as specified in 6.2.3. before a decrease in the terminal voltage of the battery prevents correct operation

Test

Connect the apparatus to a stabilized power supply set to the rated battery voltage. Decrease the supply voltage in steps of 0,1 V at intervals of at least 1 min, until the fault warning is given. Record the supply voltage at which the warning is given as UE.. At the voltage one step above the voltage at which the fault warning is given, subject the apparatus to the test gases as described in 5.3.1

Performance requirements

Battery capacity

General

Batteries of self-contained apparatus shall be capable of supplying the quiescent load of the apparatus together with the additional load of routine testing, for a period as specified in 6.2.3 before the battery fault warning is given and, thereafter, of generating an alarm or, in the absence of an alarm, of operating for a further period as prescribed in 6.2.3

Assessment

In the case of third party testing, the manufacturer shall supply details of the capacity of the recommended battery or batteries together with characteristic curves for voltage variation with time at (20 –۱۰) ”C for appropriate values of current drainage
The current drawn by the apparatus in the quiescent and routine testing conditions shall be measured

Performance requirements

The assessment of 6.2.2 shall indicate that the battery or batteries are capable of operating the apparatus as indicated in 6.2.1. for a period of 12 months. From the time when low battery voltage warning is indicated, the battery shall have sufficient capacity to give a low battery voltage warning for at least 7 days followed by an alarm signal as specified in 4.3.3 for at least 4 minutes

:The low battery voltage warning shall be indicated by either

− a suitable permanent visual indication for example a separate LED or a flashing of the fault indicator or

an acoustic indicator which may be intermittent but which shall energize for a minimum of 1 min per hour

In the case of an alarm due to CO, the alarm sound shall to be as specified in 4.3.2

Battery reversal

General

The battery reversal test shall be applied to apparatus incorporating replaceable batteries if there is any possibility of the apparatus being subjected to reversed polarity of the supply during normal battery replacement

۶٫۳٫۲ Test

a) With a new battery fitted, subject the apparatus to the test gases as described in 5.3.1. b) Remove the battery and replace it in the apparatus with reverse polarity for 10 s to 15 s.

c) Remove the battery and replace it in the apparatus with the correct polarity. Subject the apparatus to the test gases as defined in 5.3.1.

d) Remove the battery and apply a voltage to the apparatus of between UE and 0,95UE as determined in 6.1.2.

Performance requirements

During stage d) the low battery voltage warning shall be given

Battery connections

General

Where batteries are connected to a circuit board within the apparatus by flexible leads, strain relieving devices shall be fitted adjacent to both battery terminal connectors and the circuit board so that any pull on the leads shall not be transmitted to the battery terminals or circuit board

Test

Leads shall be subjected to a pull of (20 – ۲) N without jerks for 1 minute in any direction allowed by the design

Performance requirements

The strain relieving devices shall be effective in ensuring that strain is not imparted to the battery terminals or circuit board during the test. This shall be checked by visual inspection

(Annex A (informative
Health effects

A.1 Toxic effects

Carbon monoxide (CO) is a colourless, odourless non-irritating gas which is classified as a chemical asphyxiant whose toxic action is a direct result of the hypoxia produced by a given exposure.
CO is rapidly absorbed through the lungs, diffuses across the alveolar capillary membrane and is reversibly bound with haemoglobin as carboxyhaemoglobin (COHb), however a minute amount is present in the plasma. The affinity of haemoglobin for CO is over 200 times its affinity for oxygen. This reduces the oxygen carrying capacity of the blood and also has an effect on the dissociation of oxyhaemoglobin which further reduces the oxygen supply to the tissues. CO is chemically unchanged in the body and is eliminated in expired air. The elimination is determined by the same factors that applied during absorption
If the CO level in the inhaled air is constant, the level of COHb in the blood will approach an equilibrium state after several hours. However, the rate at which the equilibrium is reached depends on many factors, e.g. lung ventilation rate (physical activity) and alveolar capillary transfer, cardiac parameters, blood haemoglobin concentration, barometric pressure, oxygen and carbon dioxide concentration in the inhaled air, but the two most important factors in determining the COHb level are the CO concentration and the duration of exposure
The effects of different saturation blood COHb levels on healthy adults are shown in Table A.1.

There are other such tables and reviewing papers on the subject. The US department of Health, Education and Welfare document Air quality for CO2) refers to impairment observed in visual acuity at 3 % COHb. More recently, Kleinman et al.3). showed an impairment in exercise tolerance in normal subjects exposed to a dose of CO of 100 ppm for 1 hour

A.2 Chronic effects on high risk groups

Individuals with coronary artery disease exposed to low levels of CO showed reduced ability to exercise. The time of onset of exercise-induced angina pectoris in such patients exposed to low levels of CO is reduced.
Carbon monoxide readily crosses the placental barrier and may endanger the normal development of the foetus.
A number of high risk groups are particularly sensitive to the effects of CO because of various organ impairments or specific changes4), 5), mainly:

a) those whose oxygen carrying capacity is decreased due to anaemia or other haemoglobin disorders
b) those with increased oxygen needs such as those encountered in fever, hyperthyroidism or pregnancy
c) those with systemic hypoxia due to respiratory insufficiency
d) those with heart disease and any vascular insufficiency, such as cerebral ischaemia and peripheral vascular diseases.

A.3 Normal COHb levels
Under normal conditions all humans have low levels of COHb of between 0,3 % and 0,7 % present within the body. These levels are considered neither beneficial nor harmful.
A.4 Tobacco smoking
Tobacco smokers are exposed to significant concentrations of CO. In cigarette smokers the COHb concentration varies between 5 % – 9 % while heavy cigar smokers it may exceed 10 %

(Annex B (informative

A-deviations

A-deviation: National deviation due to regulations, the alteration of which is for the time being outside the competence of the CEN/CENELEC member
This European Standard does not fall under any Directive of the EC
In the relevant CENELEC countries these A-deviations are valid instead of the provisions of the European Standard until they have been removed

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