Description of Exposure Incidents
Source of Exposure and Type of Fuel
The survey found a total of 38 separate chronic incidents. Figure 25 shows that 60% of these were due to faulty fireplaces (usually gas) and 32% from central heating systems. In 61% of cases, problems were also identified with a flue. Amongst the unconscious group of 11 incidents, the predominance of gas fireplaces was also evident, but less pronounced in the chronic group. Thus in 50% of unconscious incidents the source was identified as the fire, with the central heating system responsible for a further 33% of incidents.
Figure 25: Source of exposure
Gas was by far the most common fuel involved in the exposure incidents, reflecting its widespread use for domestic heating. 82% of chronic incidents involved gas appliances, versus 11% solid fuel and 3% oil.
Figure 26: Type of fuel in each incident
In the unconscious cases, 64% were related to gas appliances and 9% to solid fuel. This compares to UK-wide penetration rates for domestic central heating fuels of 76% for gas, 5% for solid fuel and 3% for oil in 1992.
Length of Exposure
The average length of exposure was over 4 years for the chronic group, although the average is somewhat lengthened by one exposure of 22 years. The average length of total exposure was even longer for the unconscious group, being over five and a half years, despite the inclusion of three very short duration exposures.
Figure 27 shows the distribution of lengths of exposure for both unconscious and chronic groups. It shows that exposure commonly continued for 1 to 3 years, with a significant proportion of people suffering exposure for over five years.
Figure 27: Length of exposure
On average, nearly four years have elapsed since the source of CO was removed from the chronic group, with an elapse of two and a half years for the unconscious group. Figure 28 shows the length of time elapsed for each respondent. For many of the chronic group it was less than three years since the source of CO was removed, although there was a small group for whom the exposure was ten or more years ago.
Figure 28: Time since source removed
Location of Incidents
The people who took part in our survey had been exposed to CO in incidents across Great Britain. Figure 29 shows the distribution of incidents in different parts of the country.
Figure 29: Location of incidents
Types of Property
Figure 30 below shows the types of properties in which the exposure incidents occurred. Around 70% of all chronic exposures occurred in houses, either detached, semi or terraced. Only 19% of chronic exposures were in flats, which contradicts the conventional wisdom that CO poisoning happens most commonly in student or overseas holiday flats. The remaining 12% of chronic exposures occurred in offices, a shop and a mine.
The percentage of exposures occurring in houses rather than flats was very similar for the unconscious group, although there was a greater preponderance of detached and semi-detached houses over terraced houses. Thus 70% of unconscious exposures occurred in houses and only 10% were in flats. A further 20% of unconscious exposures were in "other" locations, which included work, a pub where the family were resident and a car (the only attempted suicide in the group).
Figure 30: Type of property
Rental/Home Ownership Characteristics
Figure 31 shows that the majority of exposures occurred in rental properties, with nearly 90% of the unconscious cases in rental domestic property and 10% in owner occupied premises. However, it is notable that nearly 40% of the chronic exposures occurred in owner occupied properties.
Figure 31: Ownership characteristics
Figure 32 shows the type of location of each incident, in terms of its urban/rural characteristics. The location of the chronic exposures was spread fairly evenly between city, town and rural/village locations. The unconscious group showed a predominance of town locations, although this may simply reflect the small size of the unconscious sample.
Figure 32: Urban/rural characteristics
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