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A study of the prevention of hot tapwater burns
Burns (1988) 14,(3).185-193 Printedin
185
GreatBritain
A study of the prevention of hot tapwater burns J. P. Murray Mount Vernon Hospital Burns Unit, Northwood,
Summary
A 4-year retrospective study of hot tapwater scalds admitted to Mount Vernon Hospital Burns Unit suggested that the three high-risk groups are young children, the elderly and the mentally and physically handicapped. A household survey was conducted of 60 homes inhabited by people over 70 years of age and 60 homes inhabited by families with toddlers to identify what measures could be taken to prevent hot tapwater scalds. The survey showed that over half of the old people did not have adequate bathing aids and that one-third of all the homes visited had a hot tapwater temperature greater than 6O”C, which is the temperature recommended by British Building Services Engineers. The survey also revealed that 50 per cent of the immersion heaters and 25 per cent of the gas boiler central heating systems produced an excessively high hot tapwater temperature. The study thus indicated that both the wider provision of bathing aids to the elderly and a nationwide programme to update old inefficient immersion heater and gas boiler central heating systems would reduce the risk of hot tapwater scalds. The installation of a ‘thermoscopic’ mixing valve, pre-set and locked at 43”C, at bath and shower outlets can totally eliminate the risk of hot tapwater scalds. At present it is not a feasible option to install these valves in every household, but there is a strong case for installing them in hospitals and residential homes for paediatric, geriatric and mentally/ physically handicapped patients.
INTRODUCTION SCALDS
thermal
from injury
AND METHODS
hot water are a common type of and theoretically are largely pre-
ventable. A 4-year retrospective study of hot tapwater scalds admitted to Mount Vernon Hospital Burns Unit showed that one-third of the patients were under 3 years of age, one-third were over 70 years of age and the majority of the 0 1988 Butterworth & Co (Publishers) 03OS-4179/88/0301X5-09 $03W
Ltd
Middlesex,
UK
other patients had a significant mental and/or physical handicap (Table I). The vast majority of the scalds occurred in bath-tubs. These three high-risk groups were also identified in retrospective reviews conducted by American researchers in Dare County, Wisconsin (Katcher, 1981) and New York State (Baptiste and Feck, 1980). Having identified the high-risk groups the next step was to identify factors which may be amenable to preventive measures. The toddler (children between 1 and 3 years of age) and old age (aged over 70) groups formed two large accessible populations for investigation, and so a household survey was performed of these two groups involving the completion of a questionnaire and the measurement of the hot tapwater and favourite bathwater temperature. After the respondent had agreed to take part in the study, his or her name, address and telephone number were recorded. The respondent was told that he or she would be contacted within the next 3 months to arrange a convenient time for the doctor conducting the survey to visit the respondent’s home. The homes were visited when there was a supply of hot water sufficient to run a bath or shower. The household survey was conducted during the first 2 weeks of December 1986. On arriving at the respondent’s house, the doctor delivered the questionnaire personally. Any problems in interpretation were discussed at the time of the interview. The doctor then took three water temperature recordings with a mercury and glass thermometer (range 0-105’C). 1. First, the hot tapwater temperature was taken by running the hot tap over l-2min and collecting several samples separately in a bucket.
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Burns (19881Vol. 14/No. 3
Table 1. Risk factors in the three age-groups
studied
Group and risk factor
No.
Babies and toddlers (mean age 79 months) No risk factor other than age Group total Children and adults (mean age 27 years) Mentally handicapped Presenile dementia Epileptic Mentally handicapped, spina bifida and epileptic Down’s syndrome Environmental Overcome by toxic fumes in bathroom Faulty shower Child’s injury caused by abuse Group total
1 1 11
Elderly (mean age 81 years) Blind and deaf No risk factor other than age Group total
1 IO 11
The highest temperature was recorded. 2. Secondly, the respondent was asked to fill a bath-tub with water at the same temperature as his or her favourite bathwater. The temperature of this water was recorded. 3. Lastly, the respondent was asked to add hot water to the normal bathwater until the water was sufficiently hot to either prevent the old person from getting into the bath or to prevent the parent from placing his or her child in the bath. This recorded temperature was called the minimum intolerable temperature.
1
RESULTS
Some of the results of the household survey are shown in Table II. It can be seen that all the toddlers received baths compared to only 82 per cent of the old people. The reason for this difference becomes apparent when Table IZZ is analysed. Many old people show a deterioriation in the control of posture and gait compounded by various arthritic conditions and yet the survey suggests that less than half of the elderly people in the UK have access to simple aids such as a grab rail or a bath seat. The height of the bath and the need to squat down low makes getting in
Tab/e II. Some results from questions asked in household survey
Item 1. Total respondents (no.) 2. Average age (yr) 3. Ratio male : female 4. No. living alone 6. No. of homes containing a bath 6. No. of homes containing a shower 7. Usual method of washing entire body (no.) a. Adult bath b. Portable baby bath c. Shower d. Washdown Total
Families with toddlers 60 2.0 30 : 30 60 (100%) 30 (50%)
Elderly 60 13”: 37 (38: 6%) 37 (62%) 58 (97%) 25 (42%)
54 (90%) 6 (10%) 0 0
49 (82%)
60
60
8 (13%) 3 (5%)
187
Murray: Prevention of hot tapwater burns Tab/e 111.Some results from elderly in household survey
questions
asked of
Elderly
/tern No. of elderly people who thought that their ability to get in and out of a bath was impaired by a. Stiff joints b. Poor balance c. Weakness of limbs d. Poor eyesight No. of homes with a. Bathroom floor safety mat Yes No No, but would find one useful b. Bath mat Yes No No, but would find one useful c. Grab rail Yes No No, but would find one useful d. Bath seat Yes No No, but would find one useful
40 24 22 13
(67%) (40%) (37%) (22%)
32 (65%) 17 (35%) 4 (8%) 21 (43%) 28 (57%) 22 (44%) 22 (44%) 27 (56%) 19 (39%) 11 (22%) 38 (78%) 9 (18%)
and out of the bath a great problem for some old people who are forced to wash themselves by taking a shower or having a washdown. On questioning the respondents about their bath routine 15 per cent of the mothers and 45
per cent of the old people took the risk of running the hot water first. However, almost all the respondents finished running the bathwater and tested its temperature before either placing the child in the bath or getting into the water themselves. The mothers placed the toddlers in water at about 37°C (range 32-41”C) whereas the old people preferred baths at about 41°C (range 34 45°C). In both groups the minimum intolerable bathwater temperature was only 311°C higher than the favourite temperature. When the respondents were asked about the hot tapwater temperature 75 per cent of the old people and 70 per cent of the mothers with toddlers felt that they could not accurately control it. Despite this, 92 per cent of the old people and 53 per cent of the mothers said that the water temperature was satisfactory. The vast majority of the mothers who thought that the hot tapwater temperature was too high said that they would appreciate help to adjust the temperature. This finding suggests that a significant number of parents with young children would co-operate if a nationwide effort was made to adjust hot tapwater temperatures. The information in Table IV shows that the types of water heating appliances used by the two groups were remarkably similar. Overall, 67.5 per cent of the homes used gas boiler central heating systems, and 22.5 per cent of the homes used an immersion heater. These results differ slightly from the national figures which are 55 per cent and 28 per cent respectively. One reason for
Table IV. Results of questions asked about hot water systems in household survey
Item 1. No. of homes in which the hot tapwater was heated by: a. the appliance which also provided the home heating Gas boiler central heating b. an appliance independent of home heating systems: Immersion heater Gas water heater Electrical water heater Fire with back boiler Coal-fired boiler Total 2. Hot tapwater temperature Mean (fsd.) Range
Families with toddlers
Elderly
Families with toddlers and elderly
42 (70%)
39 (65%)
81 (67.5%)
14 2 1 0 1
13 5 1 2 0
27 7 2 2 1
(23%) (3%) (2%) (2%)
60
(22%) (8%) (2%) (3%)
60
(22.5%) (6%) (1.5%) (1.5%) (1%)
120
(“C) 60 (+9.22) 42-82
56 ( f6.8”C) 44-74.5
58 (f8.3) 42-82
18%
Burns (1988) Vol. 14/No. 3
Tab/e V. Results of questions in household survey
asked
about
temperature
Gas boiler central Item Hot tapwater temperature Mean (k s.d.) Range
of hot water
heating systems
Immersion heaters
57.1 (k7.7) 42-78
62.1 (k9.4) 48.5-82
1°C)
ftest, gas boiler central heating systems vs. immersion heaters: t=2.75; degrees of freedom 106; P=O.O07 (orobabilitv of 1 in 143 if no difference exists between the two populations).
this difference may be that the study was done during the winter rather than the summer. More than 11 million households (over 50 per cent of households in the UK) own an immersion heater, but only about half of them use it as their sole means of heating water. Of the remainder, a substantial number use it primarily to supplement the central heating system or as an alternative to it, particularly during the summer. Hence, if the household survey had been performed during the summer, a higher percentage would have been obtained for the immersion heater systems. Another finding of the survey was that nearly all the respondents could give very few details about the type of water-heating appliance and thus it was not possible to compare water temperatures for the various types of immersion heater and gas boiler central heating systems. The mean hot tapwater temperature for the 120 homes in the survey was 58°C with a range of 42-82°C. These results are quite similar to those of an American survey carried out in Seattle in 1978 in which 57 households were visited (Feldman et al., 1978). In this study the mean temperature was 61°C and the range was 32-76°C. Table V shows that the mean temperature of the water heated by immersion heaters was significantly higher than the mean water temperature for the gas boiler central heating systems. These two appliances differ from American domestic appliances which are direct-fired oil, gas or electric water heaters and thus an exact comparison of this finding with the Seattle survey is not possible.
DISCUSSION
Several approaches to the problem of preventing hot tapwater scalds could be adopted. First, there could be more comprehensive counselling of old people and parents with toddlers and/or handicapped children about the dangers of hot tapwater. However, this approach is unlikely to be very effective. The survey showed that the bath-
room etiquette of parents with toddlers is remarkably safe and the 30 per cent positive response rate of the elderly group does not suggest that old people would take kindly to others advising them on their bath routine! One area in which the elderly are likely to be more cooperative concerns the provision of bathing aids. The survey showed that less than half of the old people had either a non-slip bath mat, a grab rail or a bath seat. Despite the undoubted value of these bathing aids and their relatively low cost (e.g. the Social Services Department provides bath mats for f2.00 and a wooden bath seat for f6.35), they are currently regarded as low priority aids. Wider provision of these aids would make bathing a lot less hazardous for many old people as well as helping to maintain their independence in personal care. Experience has shown that passive prevention measures (i.e. those not requiring ‘correct behaviour’ by the potential victims or those looking after them) tend to be more successful in preventing accidents. The passive approach to this problem would be to lower the temperature of the hot tapwater to a safe level. But what is a safe water temperature? In 1947 Moritz and Henriques performed a series of experiments on pig and human skin to find out the relative effects of time and water temperature in the causation of cutaneous burns (Moritz and Henriques, 1947). The results were remarkably similar for both species and some of these are shown in Fig. 1. After considering these experimental results, would it be possible to reduce the hot tapwater temperature to an entirely safe level? Building services engineers must consider several conflicting factors when selecting the right hot tapwater temperature, and the risk of scalding is not normally a prime consideration. Higher temperatures may be specified to make the best use of storage space and to ensure that the water is adequate for the task, e.g. washing
Murray: Prevention
of hot tapwater
189
burns 40
-
35
30
25 & ? 20 .S 15
10 40
50
60
Temperature Fig, 1. Duration of exposure cause transepidermal necrosis temperatures.
70
1°C)
to hot water required to of porcine skin at various
5
i-
dishes. On the other hand, lower temperatures are needed to avoid undue scaling of the water container (the deposit of scale increases as the temperature exceeds 6O”C, especially in hard water areas) and to reduce energy losses from the storage vessel and circulating pipework. As a result of these considerations, the Electricity Council, British Gas and the Building Research Establishment all recommend a temperature setting of 60°C in the storage vessel. Hot tapwater at a temperature of 60°C can cause a partial thickness burn in 5 s. In the USA, where more attention has been focused on the prevention of hot tapwater scalds, the National Standards Committee has established 54°C as the maximum gas water heater thermostat setting (Maley and Achauer, 1987). Water at 54°C takes about 30 s to cause a partial thickness burn and so this recommendation considerably reduces the risk of thermal injury. It is thus clear that a lowering of water heater thermostat settings to an entirely safe level is not a feasible option either in the USA or in the UK. However, analysis of Fig. 2 reveals that one-third of all the homes in the survey had a hot tapwater temperature of 60°C or over. There are 21 million households in the UK and extrapolating these results to the whole country gives a total of 7 million households with an excessively high hot tapwater temperature.
10
70 Temperature
Fig. 2. Hot tapwater
temperatures
80
90
F’C)
in household survey.
Fig. 2 also demonstrates the water temperatures of immersion heater and gas-boiler central heating systems separately. It is apparent that 50 per cent of the immersion heaters and 25 per cent of the gas boilers produced water temperatures of 60°C or greater. Indeed, a considerable proportion (25 per cent) of the immersion heaters produce temperatures of 70°C or higher. Why do immersion heaters, which are all fitted with thermostats, give rise to these dangerously high temperatures? The most common immersion heater arrangement found in the UK today is that shown in
Fig. 3. Unfortunately, the vertical entry arrangement owes its existence more to tradition and convenience of maintenance rather than good performance. The water heated by the element rises vertically to the top of the cylinder and each portion of the element heats the ascending column of water still further. The result is that a small quantity of hot water collects in a layer at the top of the storage vessel and a considerable proportion of the water does not get heated at all. Plumbers who are aware of this problem tend to set the thermostat higher rather than lower so
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Burns (1988) Vol. 14/No. 3
Hot
80 mm
water outlet
Economy 7
Thermostat
Night element
Fig. 3. Single top-entry immersion heater. The system comprises a copper cylinder containing water which is heated by a top-entry heating element. The thermostat controlling the immersion heater is usually of the bimetal rod type and senses average temperature over its entire length.
that the small volume of hot water will satisfy the needs of the household. Some immersion heaters may be giving rise to very high water temperatures because of failure of the thermostat. The average life-span of an immersion heater thermostat is about 5 years. At present, the thermostats are not regularly checked and it is highly probable that a considerable number of them are not functioning. A much better immersion heater arrangement, shown in Fig. 4, is the new high performance Economy 7 cylinder which costs g250 to install. With a low side-entry heating element there is rapid circulation of the water within the vessel. As a result all the water tends to be gradually heated and the temperature gradient between top and bottom is negligible. Gas boiler central heating systems are controlled in a variety of ways. The simplest combined heating and domestic hot water system currently in use is shown in Fig. 5. Systems of this type were installed in large numbers in the past and many of them have not been updated. Surprisingly, it has only recently become a regular practice
to control the temperature of any associated hot tapwater service by an independent thermostat. This means that for the majority of systems installed hot water for heating the cylinder is supplied at the same temperature as for the radiators and that the two factors determining the hot water temperature are the boiler thermostat setting (typically SO-85°C) and the various sources of heat loss. In many cases the boiler thermostat
Fig. 4. Two side-entry immersion heaters. The system comprises a copper cylinder which has a thick (80 mm) insulating jacket and two side-entry heating elements, the day element and the night element. The night element exploits the Economy 7 tariff in which electricity is charged at a much lower rate during 7 h at night. The Economy 7 water heating controller automatically switches on the immersion heater during the night period and, if the supply of hot water becomes depleted, the consumer can operate the heater during the day period by means of an electronic boost timer.
itself is calibrated with a number scale rather than with the actual temperature settings. One can now readily understand why three-quarters of the respondents felt that they could not accurately control the temperature of their hot tapwater. A more efficient system with full thermostatic control of the domestic hot water is shown in Fig. 6. When no space heating is required the cylinder thermostat, set at 60°C controls the stored water temperature by direct operation of the boiler. For full control a two-port valve is also required. This valve ensures positive shut-off of the hot water to the cylinder when the heating circuit is in operation, but the cylinder thermostat is satisfied. The results of this household survey indicate that a campaign to update immersion heater and gas boiler central heating systems could be quite effective. However, even if such a campaign took place, the hot tapwater temperature in nearly all homes would still be high enough to cause a cutaneous burn. Can anything be done to eliminate totally the risk of hot tapwater scalds? Several years ago, the Department of Health and Social Services faced this problem after a number of tragic accidents in which handicapped young people and elderly people in residential care were fatally scalded while bathing. At the same time, the Department of Health and Social
Murray: Prevention of hottapwater
191
burns
Hot taps Cylinder %
Pumped heating circuit
set at 80.85°C
Fig. 5. The system comprises a pumped heating circuit and a gravity circuit to the hot water cylinder. The controls are limited to a manually adjustable boiler thermostat. an on/off switch in the electrical supply to the pump and manually operated radiator control valves. Room thermostat
Boiler
Fig. 6. This system, with full thermostatic control of the stored hot water, has the addition of an electric cylinder thermostat, set at 60°C and strapped on about one-third of the way up from the bottom of the cylinder, and a two-port valve on the gravity hot water circuit. The sophisticated programmer gives a large number of programme options and the whole system, if used correctly, can considerably reduce running costs.
Security (DHSS) was also concerned about the threat of Legionnaire’s disease. The bacterium, Legionella pneumophilia, which causes this disease, can establish itself in water systems in hospitals and other institutions. Its growth is suppressed below 20°C and above 60°C. Taking these factors into account, the DHSS issued recommendations in the form of Health Building Note 23, Hospital Accommodation for Children, and Health Building Note 37, Hospital Accommodation for Elderly People. A short extract from Section 4.38 of Health Building Note 37 is given below: 4.38 ‘The domestic hot water for this department should be stored at a temperature of 60°C and the distribution controlled at a temperature of 52”C,
the reduction being achieved by a suitable mixing arrangement at the outlet from the calorifier. The safety of some elderly patients could, however, be compromised if they are allowed unsupervised use of bathing facilities that are supplied with water at this temperature. The risk can be reduced by installing at each bath and shower outlet a locally adjustable thermostatic mixing valve preset and locked to provide a blended water temperature not exceeding 43°C.’
It is widely acknowledged that one of the world’s most advanced type of thermostatic mixing valve is the ‘thermoscopic’ mixing valve. This valve was launched in 1979 and has been a great success ever since. The ‘thermoscopic’ system is extremely strong and ideally suited for ‘heavyuse’ areas such as hospitals, old people’s homes,
192
Burns (1988) Vol. 14fNo. 3 Temperature selection
hot and cold water
\ ‘Polyeutectic’ compound
Fig. 7. The closely guarded secret of the ‘thermoscopic’ unit is the precise composition of the polyeutectic or temperature-sensitive compound which is contained within four coiled arms. The assemblv also incoroorates a flexible metal bellows and a spring-loaded proportioning melhanism tailed the ‘actuator’. Depending on the temperature of the water flowing in the polyeutectic compound expands or contracts, causing the actuator to move forwards or backwards. This in turn allows more or less hot and cold water to enter the valve via the inlet ports and so maintains a set outlet temperature. schools and sports centres. The capabilities of the ‘thermoscopic’ mixing valve can be described as follows: 1. Temperature control is maintained to within 1°C of the selected temperature. 2. There is immediate response to supply pressure fluctuations. 3. If the cold supply fails there is complete shut-off in less than 2s. A section diagram of the ‘thermoscopic’ unit used in one of the mixing valves is shown in Fig. 7. This unit gives optimum temperature control within the range 30--5O”C, a range which encompasses all the favourite bathwater temperatures in the household survey. Locked versions of the valves can be set on site to deliver water at the required temperature of 43°C and then can only be reset by an authorized person so ensuring that no tampering with the temperature level takes place. Maintenance of the valve needs to be performed only once a year. The value of temperature-regulating valves has also been appreciated in the USA. A recent paper in the Journal of Burn Care and Rehabilitation states that legislation requiring the installation of appropriate tempering valves in all new dwellings now exists in three States, e.g. Connecticut, and is being considered in others (Maley and Achauer, 1987). However, the paper does
not mention how successful this legislation has been, nor does it specify how much these tempering valves cost. The type of ‘thermoscopic’ mixing valve which can be installed at domestic and hospital bath fittings costs f250 and would cost a further flO0 to fit into a house. These valves sell competitively in the UK, USA and various other developed countries, suggesting that a cheap mixing valve does not exist on the world market. Taking this into account, one wonders how realistic it is to recommend the installation of a temperature-regulating valve in every new dwelling. Various health authorities, however, may have more money at their disposal than the average houseowner and in Britain a large number of mixing valves have already been installed in hospitals and residential homes. Acknowledgements
The author would like to thank Mr R. Sanders for his interest and encouragement and the following for their kind assistance: Andrew Booth, Mount Vernon Hospital; Ruth Librarian, Barnes, Epidermiologist, St John’s Hospital, Uxbridge, Middlesex; Jennifer King, Hillingdon Social Services, Ruislip, Middlesex; Paul Bartlett, Colin Daniels and Dr Singleton, Electricity Council, London; Mr David Hill, Director of Medical Statistics, Clinical Research Centre, Harrow; Caradon Mira Ltd, Whaddon Works,
193
Murray: Prevention of hot tapwater burns
Cheltenham, Gloucestershire; Mr Ball and Dr Hall, Building Research Establishment Centre; Mr Lewin-Smith, British Gas, London; Mr Blake, Medical Photographer, Mount Vernon Hospital; Mr Shackle, Professional Artist; Department of Plastic Medical Secretaries, Surgery, Mount Vernon Hospital.
REFERENCES Baptiste M. S. and Feck G. (1980) Preventing burns. Am. J. Public Health 70, 727.
Corrqmndence
Feldman K. W., Schaller R. T., Feldman J. A. et al. (1978) Tap water scald burns in children. Paediatrics 62, 1. Katcher M. L. (1981) Scald burns from hot tapwater. JAMA
246, 1219.
Maley M. P. and Achauer B. M. (1987) Prevention of tap water scald burns. J. Burn Care Rehabil. 8, 62. Moritz A. R. and Henriques F. C. (1947) Studies of thermal injury. The relative importance of time and surface temperature in the causation of cutaneous burns. Am. J. Pathol. 23, 695.
tap water Paper
should be addressed to: Dr J. P. Murray, 9 Flexbury
INVITED COMMENT From: Evnesvuges Vel, vol. 8, 1982 (“the wellbeing of the oligophrenic”ta Danish journal, translated from the Danish. The Department of Plastic Surgery and Burns Unit of the Hvidovre Hospital, earlier located at Kommunehospitalet, Copenhagen, has worked on prevention for more than 20 years. The treatment of scalds in oligophrenic patients is, as described, a hard strain on the patients, on their next-of-kin and on the staff of the unit. This fact was for us an extra reason to try to prevent these accidents (I emphasize the word extra-because there is always a good reason to try to prevent accidents). When the accidents are analysed, we see a few basic conditions in common for most of them: 1. The accident happened in connection with bathing the patients. 2. The water which caused the scalds was water out of the hot water tapnot extra warmed water from the kitchen or anything like that. 3. Ohgophrenic persons react more slowly than normal persons--it took them longer to get away from the hot water than others and therefore the lesions became more extensive and deeper. 4. Many of them had physical handicaps also; they could not get out of the bath-tub by themselves.
accepted
Gardens,
4 November
1987
Low Fell, Gateshead,
Tyne and Wear, UK.
The solution The solution clearly was to prevent the accidents from happening. Information on the cause of the accident etc. was not enough in this case. of The solution is very simple: installation thermostats on mixer-taps, so that it is impossible to get water from the tap which is warmer than 40°C; thermostats must be installed on all taps used by oligophrenic persons. The Unit turned to the authorities in charge of oligophrenic persons. They were very interested and sent out a set of rules, requesting the installation of thermostats. Result A year later the authorities were able to note that there had been no scalds in places where the thermostats had been installed. Furthermore there was a considerable reduction in fuel oil consumption. The expenses for the installation of the thermostats was D.Cr. 300000 ($25 000). Treatment of two patients of this kind (the average number of inpatients before 1981) cost almost exactly the same. This means a 100% return of interest. There are still thermostats on all taps used by oligophrenic persons, and in 1987 we were able to note that we had not seen any scalds among the oligophrenic since the installation of thermostats. Bent Sorensen
185
GreatBritain
A study of the prevention of hot tapwater burns J. P. Murray Mount Vernon Hospital Burns Unit, Northwood,
Summary
A 4-year retrospective study of hot tapwater scalds admitted to Mount Vernon Hospital Burns Unit suggested that the three high-risk groups are young children, the elderly and the mentally and physically handicapped. A household survey was conducted of 60 homes inhabited by people over 70 years of age and 60 homes inhabited by families with toddlers to identify what measures could be taken to prevent hot tapwater scalds. The survey showed that over half of the old people did not have adequate bathing aids and that one-third of all the homes visited had a hot tapwater temperature greater than 6O”C, which is the temperature recommended by British Building Services Engineers. The survey also revealed that 50 per cent of the immersion heaters and 25 per cent of the gas boiler central heating systems produced an excessively high hot tapwater temperature. The study thus indicated that both the wider provision of bathing aids to the elderly and a nationwide programme to update old inefficient immersion heater and gas boiler central heating systems would reduce the risk of hot tapwater scalds. The installation of a ‘thermoscopic’ mixing valve, pre-set and locked at 43”C, at bath and shower outlets can totally eliminate the risk of hot tapwater scalds. At present it is not a feasible option to install these valves in every household, but there is a strong case for installing them in hospitals and residential homes for paediatric, geriatric and mentally/ physically handicapped patients.
INTRODUCTION SCALDS
thermal
from injury
AND METHODS
hot water are a common type of and theoretically are largely pre-
ventable. A 4-year retrospective study of hot tapwater scalds admitted to Mount Vernon Hospital Burns Unit showed that one-third of the patients were under 3 years of age, one-third were over 70 years of age and the majority of the 0 1988 Butterworth & Co (Publishers) 03OS-4179/88/0301X5-09 $03W
Ltd
Middlesex,
UK
other patients had a significant mental and/or physical handicap (Table I). The vast majority of the scalds occurred in bath-tubs. These three high-risk groups were also identified in retrospective reviews conducted by American researchers in Dare County, Wisconsin (Katcher, 1981) and New York State (Baptiste and Feck, 1980). Having identified the high-risk groups the next step was to identify factors which may be amenable to preventive measures. The toddler (children between 1 and 3 years of age) and old age (aged over 70) groups formed two large accessible populations for investigation, and so a household survey was performed of these two groups involving the completion of a questionnaire and the measurement of the hot tapwater and favourite bathwater temperature. After the respondent had agreed to take part in the study, his or her name, address and telephone number were recorded. The respondent was told that he or she would be contacted within the next 3 months to arrange a convenient time for the doctor conducting the survey to visit the respondent’s home. The homes were visited when there was a supply of hot water sufficient to run a bath or shower. The household survey was conducted during the first 2 weeks of December 1986. On arriving at the respondent’s house, the doctor delivered the questionnaire personally. Any problems in interpretation were discussed at the time of the interview. The doctor then took three water temperature recordings with a mercury and glass thermometer (range 0-105’C). 1. First, the hot tapwater temperature was taken by running the hot tap over l-2min and collecting several samples separately in a bucket.
188
Burns (19881Vol. 14/No. 3
Table 1. Risk factors in the three age-groups
studied
Group and risk factor
No.
Babies and toddlers (mean age 79 months) No risk factor other than age Group total Children and adults (mean age 27 years) Mentally handicapped Presenile dementia Epileptic Mentally handicapped, spina bifida and epileptic Down’s syndrome Environmental Overcome by toxic fumes in bathroom Faulty shower Child’s injury caused by abuse Group total
1 1 11
Elderly (mean age 81 years) Blind and deaf No risk factor other than age Group total
1 IO 11
The highest temperature was recorded. 2. Secondly, the respondent was asked to fill a bath-tub with water at the same temperature as his or her favourite bathwater. The temperature of this water was recorded. 3. Lastly, the respondent was asked to add hot water to the normal bathwater until the water was sufficiently hot to either prevent the old person from getting into the bath or to prevent the parent from placing his or her child in the bath. This recorded temperature was called the minimum intolerable temperature.
1
RESULTS
Some of the results of the household survey are shown in Table II. It can be seen that all the toddlers received baths compared to only 82 per cent of the old people. The reason for this difference becomes apparent when Table IZZ is analysed. Many old people show a deterioriation in the control of posture and gait compounded by various arthritic conditions and yet the survey suggests that less than half of the elderly people in the UK have access to simple aids such as a grab rail or a bath seat. The height of the bath and the need to squat down low makes getting in
Tab/e II. Some results from questions asked in household survey
Item 1. Total respondents (no.) 2. Average age (yr) 3. Ratio male : female 4. No. living alone 6. No. of homes containing a bath 6. No. of homes containing a shower 7. Usual method of washing entire body (no.) a. Adult bath b. Portable baby bath c. Shower d. Washdown Total
Families with toddlers 60 2.0 30 : 30 60 (100%) 30 (50%)
Elderly 60 13”: 37 (38: 6%) 37 (62%) 58 (97%) 25 (42%)
54 (90%) 6 (10%) 0 0
49 (82%)
60
60
8 (13%) 3 (5%)
187
Murray: Prevention of hot tapwater burns Tab/e 111.Some results from elderly in household survey
questions
asked of
Elderly
/tern No. of elderly people who thought that their ability to get in and out of a bath was impaired by a. Stiff joints b. Poor balance c. Weakness of limbs d. Poor eyesight No. of homes with a. Bathroom floor safety mat Yes No No, but would find one useful b. Bath mat Yes No No, but would find one useful c. Grab rail Yes No No, but would find one useful d. Bath seat Yes No No, but would find one useful
40 24 22 13
(67%) (40%) (37%) (22%)
32 (65%) 17 (35%) 4 (8%) 21 (43%) 28 (57%) 22 (44%) 22 (44%) 27 (56%) 19 (39%) 11 (22%) 38 (78%) 9 (18%)
and out of the bath a great problem for some old people who are forced to wash themselves by taking a shower or having a washdown. On questioning the respondents about their bath routine 15 per cent of the mothers and 45
per cent of the old people took the risk of running the hot water first. However, almost all the respondents finished running the bathwater and tested its temperature before either placing the child in the bath or getting into the water themselves. The mothers placed the toddlers in water at about 37°C (range 32-41”C) whereas the old people preferred baths at about 41°C (range 34 45°C). In both groups the minimum intolerable bathwater temperature was only 311°C higher than the favourite temperature. When the respondents were asked about the hot tapwater temperature 75 per cent of the old people and 70 per cent of the mothers with toddlers felt that they could not accurately control it. Despite this, 92 per cent of the old people and 53 per cent of the mothers said that the water temperature was satisfactory. The vast majority of the mothers who thought that the hot tapwater temperature was too high said that they would appreciate help to adjust the temperature. This finding suggests that a significant number of parents with young children would co-operate if a nationwide effort was made to adjust hot tapwater temperatures. The information in Table IV shows that the types of water heating appliances used by the two groups were remarkably similar. Overall, 67.5 per cent of the homes used gas boiler central heating systems, and 22.5 per cent of the homes used an immersion heater. These results differ slightly from the national figures which are 55 per cent and 28 per cent respectively. One reason for
Table IV. Results of questions asked about hot water systems in household survey
Item 1. No. of homes in which the hot tapwater was heated by: a. the appliance which also provided the home heating Gas boiler central heating b. an appliance independent of home heating systems: Immersion heater Gas water heater Electrical water heater Fire with back boiler Coal-fired boiler Total 2. Hot tapwater temperature Mean (fsd.) Range
Families with toddlers
Elderly
Families with toddlers and elderly
42 (70%)
39 (65%)
81 (67.5%)
14 2 1 0 1
13 5 1 2 0
27 7 2 2 1
(23%) (3%) (2%) (2%)
60
(22%) (8%) (2%) (3%)
60
(22.5%) (6%) (1.5%) (1.5%) (1%)
120
(“C) 60 (+9.22) 42-82
56 ( f6.8”C) 44-74.5
58 (f8.3) 42-82
18%
Burns (1988) Vol. 14/No. 3
Tab/e V. Results of questions in household survey
asked
about
temperature
Gas boiler central Item Hot tapwater temperature Mean (k s.d.) Range
of hot water
heating systems
Immersion heaters
57.1 (k7.7) 42-78
62.1 (k9.4) 48.5-82
1°C)
ftest, gas boiler central heating systems vs. immersion heaters: t=2.75; degrees of freedom 106; P=O.O07 (orobabilitv of 1 in 143 if no difference exists between the two populations).
this difference may be that the study was done during the winter rather than the summer. More than 11 million households (over 50 per cent of households in the UK) own an immersion heater, but only about half of them use it as their sole means of heating water. Of the remainder, a substantial number use it primarily to supplement the central heating system or as an alternative to it, particularly during the summer. Hence, if the household survey had been performed during the summer, a higher percentage would have been obtained for the immersion heater systems. Another finding of the survey was that nearly all the respondents could give very few details about the type of water-heating appliance and thus it was not possible to compare water temperatures for the various types of immersion heater and gas boiler central heating systems. The mean hot tapwater temperature for the 120 homes in the survey was 58°C with a range of 42-82°C. These results are quite similar to those of an American survey carried out in Seattle in 1978 in which 57 households were visited (Feldman et al., 1978). In this study the mean temperature was 61°C and the range was 32-76°C. Table V shows that the mean temperature of the water heated by immersion heaters was significantly higher than the mean water temperature for the gas boiler central heating systems. These two appliances differ from American domestic appliances which are direct-fired oil, gas or electric water heaters and thus an exact comparison of this finding with the Seattle survey is not possible.
DISCUSSION
Several approaches to the problem of preventing hot tapwater scalds could be adopted. First, there could be more comprehensive counselling of old people and parents with toddlers and/or handicapped children about the dangers of hot tapwater. However, this approach is unlikely to be very effective. The survey showed that the bath-
room etiquette of parents with toddlers is remarkably safe and the 30 per cent positive response rate of the elderly group does not suggest that old people would take kindly to others advising them on their bath routine! One area in which the elderly are likely to be more cooperative concerns the provision of bathing aids. The survey showed that less than half of the old people had either a non-slip bath mat, a grab rail or a bath seat. Despite the undoubted value of these bathing aids and their relatively low cost (e.g. the Social Services Department provides bath mats for f2.00 and a wooden bath seat for f6.35), they are currently regarded as low priority aids. Wider provision of these aids would make bathing a lot less hazardous for many old people as well as helping to maintain their independence in personal care. Experience has shown that passive prevention measures (i.e. those not requiring ‘correct behaviour’ by the potential victims or those looking after them) tend to be more successful in preventing accidents. The passive approach to this problem would be to lower the temperature of the hot tapwater to a safe level. But what is a safe water temperature? In 1947 Moritz and Henriques performed a series of experiments on pig and human skin to find out the relative effects of time and water temperature in the causation of cutaneous burns (Moritz and Henriques, 1947). The results were remarkably similar for both species and some of these are shown in Fig. 1. After considering these experimental results, would it be possible to reduce the hot tapwater temperature to an entirely safe level? Building services engineers must consider several conflicting factors when selecting the right hot tapwater temperature, and the risk of scalding is not normally a prime consideration. Higher temperatures may be specified to make the best use of storage space and to ensure that the water is adequate for the task, e.g. washing
Murray: Prevention
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189
burns 40
-
35
30
25 & ? 20 .S 15
10 40
50
60
Temperature Fig, 1. Duration of exposure cause transepidermal necrosis temperatures.
70
1°C)
to hot water required to of porcine skin at various
5
i-
dishes. On the other hand, lower temperatures are needed to avoid undue scaling of the water container (the deposit of scale increases as the temperature exceeds 6O”C, especially in hard water areas) and to reduce energy losses from the storage vessel and circulating pipework. As a result of these considerations, the Electricity Council, British Gas and the Building Research Establishment all recommend a temperature setting of 60°C in the storage vessel. Hot tapwater at a temperature of 60°C can cause a partial thickness burn in 5 s. In the USA, where more attention has been focused on the prevention of hot tapwater scalds, the National Standards Committee has established 54°C as the maximum gas water heater thermostat setting (Maley and Achauer, 1987). Water at 54°C takes about 30 s to cause a partial thickness burn and so this recommendation considerably reduces the risk of thermal injury. It is thus clear that a lowering of water heater thermostat settings to an entirely safe level is not a feasible option either in the USA or in the UK. However, analysis of Fig. 2 reveals that one-third of all the homes in the survey had a hot tapwater temperature of 60°C or over. There are 21 million households in the UK and extrapolating these results to the whole country gives a total of 7 million households with an excessively high hot tapwater temperature.
10
70 Temperature
Fig. 2. Hot tapwater
temperatures
80
90
F’C)
in household survey.
Fig. 2 also demonstrates the water temperatures of immersion heater and gas-boiler central heating systems separately. It is apparent that 50 per cent of the immersion heaters and 25 per cent of the gas boilers produced water temperatures of 60°C or greater. Indeed, a considerable proportion (25 per cent) of the immersion heaters produce temperatures of 70°C or higher. Why do immersion heaters, which are all fitted with thermostats, give rise to these dangerously high temperatures? The most common immersion heater arrangement found in the UK today is that shown in
Fig. 3. Unfortunately, the vertical entry arrangement owes its existence more to tradition and convenience of maintenance rather than good performance. The water heated by the element rises vertically to the top of the cylinder and each portion of the element heats the ascending column of water still further. The result is that a small quantity of hot water collects in a layer at the top of the storage vessel and a considerable proportion of the water does not get heated at all. Plumbers who are aware of this problem tend to set the thermostat higher rather than lower so
190
Burns (1988) Vol. 14/No. 3
Hot
80 mm
water outlet
Economy 7
Thermostat
Night element
Fig. 3. Single top-entry immersion heater. The system comprises a copper cylinder containing water which is heated by a top-entry heating element. The thermostat controlling the immersion heater is usually of the bimetal rod type and senses average temperature over its entire length.
that the small volume of hot water will satisfy the needs of the household. Some immersion heaters may be giving rise to very high water temperatures because of failure of the thermostat. The average life-span of an immersion heater thermostat is about 5 years. At present, the thermostats are not regularly checked and it is highly probable that a considerable number of them are not functioning. A much better immersion heater arrangement, shown in Fig. 4, is the new high performance Economy 7 cylinder which costs g250 to install. With a low side-entry heating element there is rapid circulation of the water within the vessel. As a result all the water tends to be gradually heated and the temperature gradient between top and bottom is negligible. Gas boiler central heating systems are controlled in a variety of ways. The simplest combined heating and domestic hot water system currently in use is shown in Fig. 5. Systems of this type were installed in large numbers in the past and many of them have not been updated. Surprisingly, it has only recently become a regular practice
to control the temperature of any associated hot tapwater service by an independent thermostat. This means that for the majority of systems installed hot water for heating the cylinder is supplied at the same temperature as for the radiators and that the two factors determining the hot water temperature are the boiler thermostat setting (typically SO-85°C) and the various sources of heat loss. In many cases the boiler thermostat
Fig. 4. Two side-entry immersion heaters. The system comprises a copper cylinder which has a thick (80 mm) insulating jacket and two side-entry heating elements, the day element and the night element. The night element exploits the Economy 7 tariff in which electricity is charged at a much lower rate during 7 h at night. The Economy 7 water heating controller automatically switches on the immersion heater during the night period and, if the supply of hot water becomes depleted, the consumer can operate the heater during the day period by means of an electronic boost timer.
itself is calibrated with a number scale rather than with the actual temperature settings. One can now readily understand why three-quarters of the respondents felt that they could not accurately control the temperature of their hot tapwater. A more efficient system with full thermostatic control of the domestic hot water is shown in Fig. 6. When no space heating is required the cylinder thermostat, set at 60°C controls the stored water temperature by direct operation of the boiler. For full control a two-port valve is also required. This valve ensures positive shut-off of the hot water to the cylinder when the heating circuit is in operation, but the cylinder thermostat is satisfied. The results of this household survey indicate that a campaign to update immersion heater and gas boiler central heating systems could be quite effective. However, even if such a campaign took place, the hot tapwater temperature in nearly all homes would still be high enough to cause a cutaneous burn. Can anything be done to eliminate totally the risk of hot tapwater scalds? Several years ago, the Department of Health and Social Services faced this problem after a number of tragic accidents in which handicapped young people and elderly people in residential care were fatally scalded while bathing. At the same time, the Department of Health and Social
Murray: Prevention of hottapwater
191
burns
Hot taps Cylinder %
Pumped heating circuit
set at 80.85°C
Fig. 5. The system comprises a pumped heating circuit and a gravity circuit to the hot water cylinder. The controls are limited to a manually adjustable boiler thermostat. an on/off switch in the electrical supply to the pump and manually operated radiator control valves. Room thermostat
Boiler
Fig. 6. This system, with full thermostatic control of the stored hot water, has the addition of an electric cylinder thermostat, set at 60°C and strapped on about one-third of the way up from the bottom of the cylinder, and a two-port valve on the gravity hot water circuit. The sophisticated programmer gives a large number of programme options and the whole system, if used correctly, can considerably reduce running costs.
Security (DHSS) was also concerned about the threat of Legionnaire’s disease. The bacterium, Legionella pneumophilia, which causes this disease, can establish itself in water systems in hospitals and other institutions. Its growth is suppressed below 20°C and above 60°C. Taking these factors into account, the DHSS issued recommendations in the form of Health Building Note 23, Hospital Accommodation for Children, and Health Building Note 37, Hospital Accommodation for Elderly People. A short extract from Section 4.38 of Health Building Note 37 is given below: 4.38 ‘The domestic hot water for this department should be stored at a temperature of 60°C and the distribution controlled at a temperature of 52”C,
the reduction being achieved by a suitable mixing arrangement at the outlet from the calorifier. The safety of some elderly patients could, however, be compromised if they are allowed unsupervised use of bathing facilities that are supplied with water at this temperature. The risk can be reduced by installing at each bath and shower outlet a locally adjustable thermostatic mixing valve preset and locked to provide a blended water temperature not exceeding 43°C.’
It is widely acknowledged that one of the world’s most advanced type of thermostatic mixing valve is the ‘thermoscopic’ mixing valve. This valve was launched in 1979 and has been a great success ever since. The ‘thermoscopic’ system is extremely strong and ideally suited for ‘heavyuse’ areas such as hospitals, old people’s homes,
192
Burns (1988) Vol. 14fNo. 3 Temperature selection
hot and cold water
\ ‘Polyeutectic’ compound
Fig. 7. The closely guarded secret of the ‘thermoscopic’ unit is the precise composition of the polyeutectic or temperature-sensitive compound which is contained within four coiled arms. The assemblv also incoroorates a flexible metal bellows and a spring-loaded proportioning melhanism tailed the ‘actuator’. Depending on the temperature of the water flowing in the polyeutectic compound expands or contracts, causing the actuator to move forwards or backwards. This in turn allows more or less hot and cold water to enter the valve via the inlet ports and so maintains a set outlet temperature. schools and sports centres. The capabilities of the ‘thermoscopic’ mixing valve can be described as follows: 1. Temperature control is maintained to within 1°C of the selected temperature. 2. There is immediate response to supply pressure fluctuations. 3. If the cold supply fails there is complete shut-off in less than 2s. A section diagram of the ‘thermoscopic’ unit used in one of the mixing valves is shown in Fig. 7. This unit gives optimum temperature control within the range 30--5O”C, a range which encompasses all the favourite bathwater temperatures in the household survey. Locked versions of the valves can be set on site to deliver water at the required temperature of 43°C and then can only be reset by an authorized person so ensuring that no tampering with the temperature level takes place. Maintenance of the valve needs to be performed only once a year. The value of temperature-regulating valves has also been appreciated in the USA. A recent paper in the Journal of Burn Care and Rehabilitation states that legislation requiring the installation of appropriate tempering valves in all new dwellings now exists in three States, e.g. Connecticut, and is being considered in others (Maley and Achauer, 1987). However, the paper does
not mention how successful this legislation has been, nor does it specify how much these tempering valves cost. The type of ‘thermoscopic’ mixing valve which can be installed at domestic and hospital bath fittings costs f250 and would cost a further flO0 to fit into a house. These valves sell competitively in the UK, USA and various other developed countries, suggesting that a cheap mixing valve does not exist on the world market. Taking this into account, one wonders how realistic it is to recommend the installation of a temperature-regulating valve in every new dwelling. Various health authorities, however, may have more money at their disposal than the average houseowner and in Britain a large number of mixing valves have already been installed in hospitals and residential homes. Acknowledgements
The author would like to thank Mr R. Sanders for his interest and encouragement and the following for their kind assistance: Andrew Booth, Mount Vernon Hospital; Ruth Librarian, Barnes, Epidermiologist, St John’s Hospital, Uxbridge, Middlesex; Jennifer King, Hillingdon Social Services, Ruislip, Middlesex; Paul Bartlett, Colin Daniels and Dr Singleton, Electricity Council, London; Mr David Hill, Director of Medical Statistics, Clinical Research Centre, Harrow; Caradon Mira Ltd, Whaddon Works,
193
Murray: Prevention of hot tapwater burns
Cheltenham, Gloucestershire; Mr Ball and Dr Hall, Building Research Establishment Centre; Mr Lewin-Smith, British Gas, London; Mr Blake, Medical Photographer, Mount Vernon Hospital; Mr Shackle, Professional Artist; Department of Plastic Medical Secretaries, Surgery, Mount Vernon Hospital.
REFERENCES Baptiste M. S. and Feck G. (1980) Preventing burns. Am. J. Public Health 70, 727.
Corrqmndence
Feldman K. W., Schaller R. T., Feldman J. A. et al. (1978) Tap water scald burns in children. Paediatrics 62, 1. Katcher M. L. (1981) Scald burns from hot tapwater. JAMA
246, 1219.
Maley M. P. and Achauer B. M. (1987) Prevention of tap water scald burns. J. Burn Care Rehabil. 8, 62. Moritz A. R. and Henriques F. C. (1947) Studies of thermal injury. The relative importance of time and surface temperature in the causation of cutaneous burns. Am. J. Pathol. 23, 695.
tap water Paper
should be addressed to: Dr J. P. Murray, 9 Flexbury
INVITED COMMENT From: Evnesvuges Vel, vol. 8, 1982 (“the wellbeing of the oligophrenic”ta Danish journal, translated from the Danish. The Department of Plastic Surgery and Burns Unit of the Hvidovre Hospital, earlier located at Kommunehospitalet, Copenhagen, has worked on prevention for more than 20 years. The treatment of scalds in oligophrenic patients is, as described, a hard strain on the patients, on their next-of-kin and on the staff of the unit. This fact was for us an extra reason to try to prevent these accidents (I emphasize the word extra-because there is always a good reason to try to prevent accidents). When the accidents are analysed, we see a few basic conditions in common for most of them: 1. The accident happened in connection with bathing the patients. 2. The water which caused the scalds was water out of the hot water tapnot extra warmed water from the kitchen or anything like that. 3. Ohgophrenic persons react more slowly than normal persons--it took them longer to get away from the hot water than others and therefore the lesions became more extensive and deeper. 4. Many of them had physical handicaps also; they could not get out of the bath-tub by themselves.
accepted
Gardens,
4 November
1987
Low Fell, Gateshead,
Tyne and Wear, UK.
The solution The solution clearly was to prevent the accidents from happening. Information on the cause of the accident etc. was not enough in this case. of The solution is very simple: installation thermostats on mixer-taps, so that it is impossible to get water from the tap which is warmer than 40°C; thermostats must be installed on all taps used by oligophrenic persons. The Unit turned to the authorities in charge of oligophrenic persons. They were very interested and sent out a set of rules, requesting the installation of thermostats. Result A year later the authorities were able to note that there had been no scalds in places where the thermostats had been installed. Furthermore there was a considerable reduction in fuel oil consumption. The expenses for the installation of the thermostats was D.Cr. 300000 ($25 000). Treatment of two patients of this kind (the average number of inpatients before 1981) cost almost exactly the same. This means a 100% return of interest. There are still thermostats on all taps used by oligophrenic persons, and in 1987 we were able to note that we had not seen any scalds among the oligophrenic since the installation of thermostats. Bent Sorensen