31-07-2012, 11:38 AM
Study on the Provision of Carbon Monoxide Detectors Under The Building Regulations
[attachment=29644]
Introduction
GASTEC at CRE (GaC) were commissioned by Communities and Local Government to undertake a desk-based study on the provision of carbon monoxide (CO) detectors under the building regulations.
This review has carried out a detailed study into the available technology. Included in this review is a comparison of the current prices of detectors available on the UK market. Also compared were the technical specifications of the detectors, including the standard to which they conform (and hence the levels at which the alarm will operate) and the type of power required to operate the detector.
The next part of this study includes a review of the reliability and location of the alarms. This has included looking at the number of cases where CO detectors have been present but have not alarmed when they should have done.
In order to understand the current situation fully, a detailed analysis of the deaths and injuries caused by CO poisoning has been carried out. This was partly to clarify the numbers which are often quoted, but include factors such as suicide, which are not relevant to this study. Another reason for analysing the casualty statistics was in order that a detailed cost benefit analysis could be carried out.
The cost benefit analysis forms the final part of this report and gives a cost benefit ratio. This forms part of the basis on which GaC make the final recommendations to the Department.
8 | Study on the Provision of Carbon Monoxide Detectors Under The Building Regulations
Review of available technology
A market survey of the available technology has been carried out and all the technical specifications of the various CO detectors compared. The major factors included in this comparison were cost, lifetime, alarm levels and the standard to which the CO detectors had been tested. The market survey included the most commonly available brands on sale in the UK. These were Honeywell, Fire Angel, Kidde, BRK Dicon and Ei.
All the detectors researched here conform to the latest European and British Standard which is BS EN 50291:2001 apart from the detector manufactured by BRK Dicon and this conforms to the latest North American Standard UL 2034. The alarm conditions as stated by BS EN 50291:2001 are shown below in Table 1.
The health effects of CO are shown in Table 2 below in terms of the percentage of carboxyhaemoglobin (COHb) in the blood. CO is a colourless, odourless gas which is rapidly absorbed through the lungs. It reversibly binds with haemoglobin and forms COHb. CO combines with haemoglobin over 200 times more readily than oxygen does and therefore it reduces the oxygen carrying capacity of the blood. CO further reduces the oxygen carrying capacity of the blood by having an effect on the dissociation of oxyhaemoglobin.
The lifetime of the CO detector unit is also a major factor which was compared in the market survey. The majority of detectors on the UK market have a lifetime which directly relates to the lifetime of the sensor unit. In most cases this means the unit has to be replaced at the end of the sensor lifetime. In a few cases the sensor can be replaced and so the lifetime of the unit is twice as long. It is recommended by the manufacturer that the unit be replaced after two sensor lifetimes. Of the detectors looked at in this survey, only the Ei detectors were available to buy with replaceable sensors. The effect of being able to buy a new sensor means the unit lifetime is increased from 5 to 10 years. All the remaining detectors which were considered in this study had lifetimes ranging from 5 to 7 years, with the average lifetime being 6 years. It is this average which has been used for the cost benefit analysis in this report. This average has been calculated using the product literature from a range of detectors available on the UK market.
The cost of CO detectors available on the UK market varies in part due to the range of different manufacturers, but also due to the variability in power options. There are four main types of unit available on the market and these are: mains 230 V with battery backup, mains without battery backup, units with replaceable batteries and units with non-replaceable batteries.
Study on the Provision of Carbon Monoxide Detectors Under The Building Regulations
There are advantages and disadvantages associated with each way in which the unit is powered. In the case of a mains-only detector, the obvious disadvantage is that in the case of a power cut, the detector will not be able to function, but the advantage is that is not easy to tamper with. Those detectors which have non-replaceable batteries are much more tamper proof, but because they are in a sealed unit it means the lifetime of the detector is restricted to the lifetime of the batteries.
A mains powered detector with battery backup has the major advantage that in the event of a power cut the detector will still alarm if CO is detected. Such a scenario might arise in the event of an electric power cut initiating the use of an old gas fire. This advantage is also realised if the power supply is cut to the house for any other reason such as maintenance. The only disadvantage to this type of detector would occur if the batteries were removed (for future replacement or accidentally) and there was also a power cut, but the chances of this are minimal and the advantages far outweigh this disadvantage.
It must be noted here that there are mains powered detectors available with a cord and plug but this is not considered tamper proof as it could be unplugged. A more tamper proof option is to have the detector hard wired in a similar way to, for example, a standard smoke alarm. This option means that not only does the detector itself cost more to purchase initially but also there would be a fee required to fit the detector by a qualified electrician. At current prices, it is estimated that this installation cost would be in the range £90–150. However, it is anticipated that if CO detectors were to become compulsory under building regulations then the economies of scale could result in some reduction in this installation fee.
From this analysis several major points can be made to help the cost benefit analysis. The first of these points is the price per year of buying and maintaining a CO detector. From the range looked at in this study, the average price of a unit was £31.37. Owing to market sensitivity, this average is not a weighted average, as it was calculated by looking at the prices of the detectors considered in this study. The detectors looked at ranged from as little as £17.13 per unit to £68.88 per unit. Two detectors of these considered contain replaceable sensors (both Ei detectors) – these detectors have all the same functions but one has a digital display and the other does not. These are both mains powered detectors with replaceable sensors. The price of the replaceable sensors is £21.30 and once fitted they give the unit another 5 years of life.
Chapter 3 Review of available technology | 11
If CO detectors were to be compulsory under building regulations then almost certainly the price of each unit would be reduced due to the economies of scale, however as CO detectors are already produced at the level of tens of thousands per year such reductions may be modest.
Due to the variation in lifetime, cost and power options, one type of detector has been chosen to use as a base case scenario for the cost benefit analysis. The detector to be used as this base case scenario is one with a sealed battery unit which lasts the lifetime of the detector. This means that at the end of the lifetime, the detector should be thrown away and a new one installed. Of the range of detectors looked at for the purposes of this study, there are two which are of this type. The average price of these two units is £23.62 and it is this cost which will be used. As these detectors do not draw any mains power or require replacement batteries or sensors, no maintenance cost will occur. However, it should be noted that a detector running on mains power with battery backup would cost in the region of £1.50 per year to operate including the cost of replacement batteries.
Study on the Provision of Carbon Monoxide Detectors Under The Building Regulations
There are several recommendations available to the public as to the quantity and location of CO detectors in their dwellings.
In the case of installing a single detector, the recommendations generally state that the detector should be placed higher up in the room but not too close to the combustion appliance. Placing the detector higher up means it is more likely to sense CO quickly as the CO is entrained in the warm air from the combustion appliance.
It is also generally recommended that if a number of CO detectors can be installed then one should be placed in every room in the dwelling which has a combustion appliance fitted in it.
There are some specific cases where advice differs from the generalisations mentioned above. By way of example, in the case of bedsits, the advice is to place the detector nearest the sleeping area to alert occupants when asleep. If the combustion appliance is located in a cellar or boiler room, the detector should be placed just outside the door to this room in order that the alarm would be heard if the detector went off.
[attachment=29644]
Introduction
GASTEC at CRE (GaC) were commissioned by Communities and Local Government to undertake a desk-based study on the provision of carbon monoxide (CO) detectors under the building regulations.
This review has carried out a detailed study into the available technology. Included in this review is a comparison of the current prices of detectors available on the UK market. Also compared were the technical specifications of the detectors, including the standard to which they conform (and hence the levels at which the alarm will operate) and the type of power required to operate the detector.
The next part of this study includes a review of the reliability and location of the alarms. This has included looking at the number of cases where CO detectors have been present but have not alarmed when they should have done.
In order to understand the current situation fully, a detailed analysis of the deaths and injuries caused by CO poisoning has been carried out. This was partly to clarify the numbers which are often quoted, but include factors such as suicide, which are not relevant to this study. Another reason for analysing the casualty statistics was in order that a detailed cost benefit analysis could be carried out.
The cost benefit analysis forms the final part of this report and gives a cost benefit ratio. This forms part of the basis on which GaC make the final recommendations to the Department.
8 | Study on the Provision of Carbon Monoxide Detectors Under The Building Regulations
Review of available technology
A market survey of the available technology has been carried out and all the technical specifications of the various CO detectors compared. The major factors included in this comparison were cost, lifetime, alarm levels and the standard to which the CO detectors had been tested. The market survey included the most commonly available brands on sale in the UK. These were Honeywell, Fire Angel, Kidde, BRK Dicon and Ei.
All the detectors researched here conform to the latest European and British Standard which is BS EN 50291:2001 apart from the detector manufactured by BRK Dicon and this conforms to the latest North American Standard UL 2034. The alarm conditions as stated by BS EN 50291:2001 are shown below in Table 1.
The health effects of CO are shown in Table 2 below in terms of the percentage of carboxyhaemoglobin (COHb) in the blood. CO is a colourless, odourless gas which is rapidly absorbed through the lungs. It reversibly binds with haemoglobin and forms COHb. CO combines with haemoglobin over 200 times more readily than oxygen does and therefore it reduces the oxygen carrying capacity of the blood. CO further reduces the oxygen carrying capacity of the blood by having an effect on the dissociation of oxyhaemoglobin.
The lifetime of the CO detector unit is also a major factor which was compared in the market survey. The majority of detectors on the UK market have a lifetime which directly relates to the lifetime of the sensor unit. In most cases this means the unit has to be replaced at the end of the sensor lifetime. In a few cases the sensor can be replaced and so the lifetime of the unit is twice as long. It is recommended by the manufacturer that the unit be replaced after two sensor lifetimes. Of the detectors looked at in this survey, only the Ei detectors were available to buy with replaceable sensors. The effect of being able to buy a new sensor means the unit lifetime is increased from 5 to 10 years. All the remaining detectors which were considered in this study had lifetimes ranging from 5 to 7 years, with the average lifetime being 6 years. It is this average which has been used for the cost benefit analysis in this report. This average has been calculated using the product literature from a range of detectors available on the UK market.
The cost of CO detectors available on the UK market varies in part due to the range of different manufacturers, but also due to the variability in power options. There are four main types of unit available on the market and these are: mains 230 V with battery backup, mains without battery backup, units with replaceable batteries and units with non-replaceable batteries.
Study on the Provision of Carbon Monoxide Detectors Under The Building Regulations
There are advantages and disadvantages associated with each way in which the unit is powered. In the case of a mains-only detector, the obvious disadvantage is that in the case of a power cut, the detector will not be able to function, but the advantage is that is not easy to tamper with. Those detectors which have non-replaceable batteries are much more tamper proof, but because they are in a sealed unit it means the lifetime of the detector is restricted to the lifetime of the batteries.
A mains powered detector with battery backup has the major advantage that in the event of a power cut the detector will still alarm if CO is detected. Such a scenario might arise in the event of an electric power cut initiating the use of an old gas fire. This advantage is also realised if the power supply is cut to the house for any other reason such as maintenance. The only disadvantage to this type of detector would occur if the batteries were removed (for future replacement or accidentally) and there was also a power cut, but the chances of this are minimal and the advantages far outweigh this disadvantage.
It must be noted here that there are mains powered detectors available with a cord and plug but this is not considered tamper proof as it could be unplugged. A more tamper proof option is to have the detector hard wired in a similar way to, for example, a standard smoke alarm. This option means that not only does the detector itself cost more to purchase initially but also there would be a fee required to fit the detector by a qualified electrician. At current prices, it is estimated that this installation cost would be in the range £90–150. However, it is anticipated that if CO detectors were to become compulsory under building regulations then the economies of scale could result in some reduction in this installation fee.
From this analysis several major points can be made to help the cost benefit analysis. The first of these points is the price per year of buying and maintaining a CO detector. From the range looked at in this study, the average price of a unit was £31.37. Owing to market sensitivity, this average is not a weighted average, as it was calculated by looking at the prices of the detectors considered in this study. The detectors looked at ranged from as little as £17.13 per unit to £68.88 per unit. Two detectors of these considered contain replaceable sensors (both Ei detectors) – these detectors have all the same functions but one has a digital display and the other does not. These are both mains powered detectors with replaceable sensors. The price of the replaceable sensors is £21.30 and once fitted they give the unit another 5 years of life.
Chapter 3 Review of available technology | 11
If CO detectors were to be compulsory under building regulations then almost certainly the price of each unit would be reduced due to the economies of scale, however as CO detectors are already produced at the level of tens of thousands per year such reductions may be modest.
Due to the variation in lifetime, cost and power options, one type of detector has been chosen to use as a base case scenario for the cost benefit analysis. The detector to be used as this base case scenario is one with a sealed battery unit which lasts the lifetime of the detector. This means that at the end of the lifetime, the detector should be thrown away and a new one installed. Of the range of detectors looked at for the purposes of this study, there are two which are of this type. The average price of these two units is £23.62 and it is this cost which will be used. As these detectors do not draw any mains power or require replacement batteries or sensors, no maintenance cost will occur. However, it should be noted that a detector running on mains power with battery backup would cost in the region of £1.50 per year to operate including the cost of replacement batteries.
Study on the Provision of Carbon Monoxide Detectors Under The Building Regulations
There are several recommendations available to the public as to the quantity and location of CO detectors in their dwellings.
In the case of installing a single detector, the recommendations generally state that the detector should be placed higher up in the room but not too close to the combustion appliance. Placing the detector higher up means it is more likely to sense CO quickly as the CO is entrained in the warm air from the combustion appliance.
It is also generally recommended that if a number of CO detectors can be installed then one should be placed in every room in the dwelling which has a combustion appliance fitted in it.
There are some specific cases where advice differs from the generalisations mentioned above. By way of example, in the case of bedsits, the advice is to place the detector nearest the sleeping area to alert occupants when asleep. If the combustion appliance is located in a cellar or boiler room, the detector should be placed just outside the door to this room in order that the alarm would be heard if the detector went off.