Zoe Anderson, 24, was found dead at her father’s home in Lansdown, Bath, in December 2010.
Andrew Hartley, 36, of Bath New Road in Radstock, Somerset, was found guilty of manslaughter by gross negligence.
But how often are workmen and women jailed as a result of health and safety breaches?
According to the Department of Healthh there are approximately 50 accidental deaths from acute CO poisoning in England and Wales and over 200 non-fatal poisonings which require hospital admission each year.
Deaths can be as a result of various factors: blocked chimneys, car engines running in integral garages with inadequate ventilation and poor installation or maintenance of fossil fuel or wood-burning appliances.
‘Single figures’
But court cases are still relatively rare.
A spokesman for the Health and Safety Executive (HSE) said about 15 CO poisoning-related deaths are referred to them each year
He said: “The number of people jailed for health and safety breaches each year is a relatively small number – we’re talking single figures each year.
“Certainly of those people jailed for health and safety offences, a big proportion are gas fitters.
“That’s for two reasons – they are often self-employed so can be held accountable rather than a company and secondly unsafe gas work is a very serious offence which can put a large number of lives at risk.”
While court case numbers are small, much has been done to raise awareness about the risks of faulty boilers.
Campaigns have also been run or supported by individuals affected by CO poisoning: in April a woman whose teenage daughter was killed by carbon monoxide poisoning from a badly fitted fire urged people to invest in a CO alarm at home.
‘Silent killer’
Anne Mitchell, from Cwmbran, in Torfaen, Wales, found her daughter Alex, 14, dead at home in 2005.
The man who carried out the work to the fire was later jailed for two years.
Prosecutions are not just brought about following deaths: in May last year a man from Essex who posed as a qualified gas fitter was fined £23,000 after an investigation by the Health and Safety Executive.
And it is not just gas fitters who can be jailed for not ensuring safety standards are met.
In May 2011 a landowner was jailed for ignoring safety issues at a car park at The Burrows in St Ives.
The Royal Society for the Prevention of Accidents (RoSPA) runs a CO poisoning awareness campaign.
Ashley Martin, RoSPA’s public health co-ordinator and Be Gas Safe programme manager, said homeowners should ensure an engineer is registered through the Gas Safe Register – a safety body that replaced Corgi in April 2009.
He said: “Always check that an engineer’s capabilities, which are listed on the back of his or her identity card, include the job that needs doing.
“Carbon monoxide is known as the silent killer – you can’t see it, hear it, or taste it.”
“Start Quote
If engineers cut corners they can expect to be held to account for their actions”
End Quote Spokesman HSE
He said signs of CO poisoning included prolonged flu-like symptoms, particularly in children, the elderly and maybe even pets, gas appliances burning with orange instead of blue flames, sooty stains on or near appliances, excessive condensation in the room and coal or wood fires that burn slowly or go out.
It is a legal requirement for anyone who carries out gas work to be on the register.
Registration requires an engineer to prove their technical expertise, including qualifications and certificates of competence, which they are retested on every five years.
Speaking about the Andrew Hartley case, the HSE spokesman said: “The householder in this case did the right thing – they employed a registered gas engineer who was legally allowed to work on gas appliances.
“However, he failed to apply competence and expertise, with tragic consequences.
“If engineers cut corners they can expect to be held to account for their actions.
“Not only will they be removed from the register, they can also face prosecution and, as in this case, imprisonment.”