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The Threat of CO Poisoning

Published: 10th Oct 2006


How employers can protect their employees at work, AND at home

Carbon monoxide has been listed under COSHH ever since the regulations were published, so it has been necessary for companies to provide a means of detection as a duty of care to their employees.

Toxic gas detection instruments and systems are common place in industrial installations, but in some cases, the employee is more at risk of CO poisoning when they finish their working day and return home. Official statistics claim around 50 people die at home each year as a result of carbon monoxide (CO) poisoning in the UK. But some experts estimate the real figure is ten times higher due to the number of cases that continue to go undetected.

In last year’s CoGDEM article in this magazine, some case studies of industrial gas incidents were featured. Through this article, it is hoped to educate employers as to the actual risks that their employees face, and how simple awareness of the sources of CO poisoning can save lives.

A ‘silent killer’

Industrial processes such as steel-making are well documented sources of carbon monoxide. Considered to be one of the leading causes of death and injury worldwide, and a major public health problem, CO is an invisible gas with the same density as air. A common by-product of incomplete combustion, it is produced when fossil fuel appliances burn - like a furnace, boiler, coal fire, wood burning stove, range oven, water heater or space heater - without sufficient air. It is also a natural by-product of cigarette smoke.

The effects are deadly, as this highly poisonous gas has the potential to kill, or cause permanent neurological damage, in a matter of hours. Breathing air that contains as little as 0.1% CO by volume can be fatal; a concentration of around 1% can cause death within a few minutes. However, it’s prolonged exposure to small amounts of the gas over time that poses the biggest, and most undetectable, threat to human safety.

When inhaled, CO reacts with haemoglobin - the red blood pigment that normally carries oxygen to all parts of the body. Naturally attracted to the haemoglobin, CO is 210 times more efficient at attachment than oxygen so it takes the place of oxygen in the blood ultimately causing oxygen starvation throughout the body. This produces a toxic compound in the blood called carboxyhaemoglobin (COHb.).

As levels of COHb in the body rise, it causes flu-like symptoms including headaches, nausea, vomiting, dizziness and fatigue - which can easily be misdiagnosed by both patients and medical professionals alike. Symptoms can eventually lead to loss of consciousness, brain damage and death.

The hidden dangers

Under the Health and Safety at Work Act 1974, employees are better protected against carbon monoxide whilst at work than they are at home. Many people are commonly exposed to CO in their own home, often while asleep, and most at risk are the elderly and young children. Statistics show that of all individuals affected in 2005, 27% were under-five, compared to 15% of children aged between five and 14. In the same period, the percentage of fatal victims aged 65 and over was 38% - more than double that of 26 to 40 year olds.

Other typical victims include students, who are predominantly placed at risk due to poor domestic safety measures. According to a housing and health poll by the National Union of Students, a fifth of UK students lived in houses without smoke detectors in 2001, and nearly half surveyed had never seen a gas safety certificate - the document which landlords are legally obliged to display under the Gas Safety (Installation and Use) Regulations 1998.

These Regulations place duties on landlords to ensure that gas appliances, fittings and flues provided for tenants’ use are safe, properly fitted and regularly maintained. Failure to do so could result in prosecution, with a maximum penalty of unlimited fines and the possibility of imprisonment.

The stark reality

A study by MORI, commissioned by the Department of Trade and Industry, into consumer knowledge of CO found very few people linked domestic hazards to oil, coal or even wood - only gas. Just one in four were aware that poor ventilation could result in the build up of CO, and three in ten households had not serviced a gas boiler or heating system for over a year. Even more concerning, CO poisoning was generally viewed as something that only ever ‘ happens in industry’ or ‘happens to other people’; for example, students living in bed sits.

The truth is infinitely more sobering. More people are killed in owner-occupied accommodation than rented; the most common cause is inadequate ventilation or poor maintenance of appliances, and breathing in this colourless, odourless gas can prove fatal in just a matter of hours.

What’s more, an alarming rise in carbon monoxide deaths has started to occur. Some 20 fatalities occurred in the 12 months from March 2005 compared to 11 during 2003/4. This increase - the first for many years - throws into doubt a Government target set at the start of the decade for no more than 20 deaths in 2010. Add to this a further 214 injuries in 2004/5 - up from 174 the previous year - and 117 incidents, compared to 93 in 2003/4, and the problem is undeniably escalating at a rapid rate.

Help is at hand

CoGDEM, the Council of Gas Detection and Environmental Monitoring, has been the active Trade Association for the industry for over 30 years. Its member companies include all of the companies that industrial users of gas detecting instrumentation will be familiar with. CoGDEM has produced guidance for the selection, use and calibration of industrial safety instruments, and sat on many BSI and European committees that have produced standards in common use today.

Those CoGDEM member companies that manufacture CO alarms suitable for domestic use want to get industrial employers and safety experts to publicise and raise awareness of the gas risks in the homes of their employees. To achieve this, an industry collective has been set up to help re-educate everyone on the dangers of CO; how to protect homes from harmful emissions, and new measures to prevent CO leakage altogether.

As CoGDEM’s PR spokesperson Zoe Forman explains, “Deaths and irreparable damage to health caused by CO poisoning are made even more tragic by the fact that they can so easily be avoided”.

“But to help prevent such needless fatalities, a step change in the public’s perception of CO dangers needs to be addressed. We need to proactively get the message out there again that this gas is deadly and it will take innocent lives - but that there are also many simple and inexpensive ways of cutting that risk down to zero”.

“National campaigns may have increased awareness before, but they naturally have a relative shelf-life. People soon forget, and the focus soon shifts to the next publicised danger. Through the CoGDEM campaign, we want everyone in the UK to get CO-savvy again and start protecting themselves properly before it’s too late.”

CoGDEM will run a 12-month campaign to raise CO awareness and provide practical and specific safety advice. This hands-on approach will help to ensure that all tenants and property owners put health and safety at the top of their list of priorities - an objective that has recently thrown gas suppliers and the Government into a heated dispute.

The two are at odds over who is to blame for the shock rise in the number of deaths from CO poisoning in the last few years. One leading gas supplier is calling for a new law that requires fires and boilers to be tested and certified in every home for sale on the market, largely to bring private properties in line with the HSE-regulated rental sector. The Government, however, is pushing for industry suppliers to fund a £multi-million national advertising campaign warning of the dangers of faulty domestic equipment.

Through the work of the new CoGDEM task force, however, both of these objectives may well be met. The Group’s first action is to inform people about the most up-to-date protection available for the home, whilst addressing common concerns that are stopping the public from actually using them.

Innocent lives lost

A chemical asphyxiate, CO poisoning is not choosy about its victims. Incidents frequently occur in a variety of environments; often, those where the installation of adequate safety measures are taken for granted.

For example, tragedy hit a French family in 2005 while living in a £1m luxury rented property in London. CO poisoning claimed the innocent life of a six year old girl due to emissions leaking out of the boiler and into her bedroom. It was initially thought she had meningitis. The landlord was taken to Westminster Coroners Court, where it was ruled that the faulty boiler was to blame. He had failed to get a certified engineer to carry out compulsory annual checks on the boiler as required by the HSE.

A woman in her 30’s from Oxford also recently died of CO poisoning, this time as a result of a faulty gas boiler that hadn’t been fixed properly by a leading UK energy retailer. The inquest was told that the gas boiler had received two service visits and around ten call-out visits over an 18 month period, including one the day before CO poisoning claimed the woman’s life.

On this last occasion, an adjustment was made to a gas valve on the boiler which left it incapable of locking out - meaning it was still not working properly, as well as leaking CO. The woman had visited a hospital in Oxford, complaining of feeling sick, dizzy and suffering from anxiety, but doctors were unable to find anything wrong and discharged her. Within 24 hours she was discovered by her flat-mate overcome with fumes and lying on the bedroom floor.

Common causes

The most common cause of fatal accidents, according to Department of Trade and Industry statistics, are faulty or poorly installed gas appliances (59%) - a number of which result from a blocked or leaky flue (a passageway that usually draws fumes and exhausts them harmlessly outside.) Defective gas fires and cookers shoulder much of the blame, with the burning of solid fuels such as coal fires and central heating systems (17%) are next in line. Gas stoves, paraffin heaters, solid fuel powered stoves and room heaters are also all potential sources.

But common ignorance surrounding the danger signs is putting public safety at risk even more. According to CORGI, almost 50% of people would be unable to recognise the warning signs of CO poisoning. One in three people surveyed do not know what colour the flame on a gas boiler will burn if there are traces of carbon monoxide (orange or yellow); and one in twenty thinks that it actually should burn orange or yellow, rather than blue. The actual danger signs include soot or stain marks on appliances; a yellow or orange lazy flame in place of crisp and blue one, and condensation in the room where the appliance is installed.

Reading the signs

Accidental CO poisoning is also known to peak during the winter months, in line with increased use of indoor central heating systems and reduced external ventilation. Given that this seasonal rise coincides with the annual increase in cases of influenza, and with such similarity in their symptoms, many cases of mild CO poisoning are most probably attributed to winter bugs or viral infections.

Research suggests that as many as 10% of people each year could be affected in this way, yet almost 100% of people surveyed would not consider flu-like indications to be anything other than a seasonal illness. Alarmingly, 32% of elderly people admitted to lacking energy and suffering from severe fatigue during the winter but very few would think to go to the doctor .

Although CO poisoning is difficult to prevent - and diagnose - the risk of it causing serious injury or death can be significantly limited with a CO alarm. As nearly 75% of homes in the UK still don’t have one fitted, CoGDEM’s first task is to increase public confidence and promote CO alarms as a highly effective way of protecting people in the home.

Prevention methods

Whilst they offer no substitute for safe appliances, CO alarms provide an extremely valuable warning system. “Contrary to popular perception, a CO alarm does not operate like a smoke alarm. In a fire, the smoke alarm is triggered when it detects particles of smoke because the danger is immediate. A CO alarm is designed to monitor the air. So when a high peak level of CO is recorded, or if the alarm detects low level CO presence over a longer period of time, the alarm will sound. These detectors constantly monitor and use a logic processor to calculate the potential COHB risk before it becomes dangerous. An 85 decibel warning bell sounds when hazardous levels of the gas are detected over a period of time,” describes Zoe Forman.

New European standards for detectors have also toughened up the quality of sensors and alarms, principally in response to a HSE report in 2000 claiming domestic CO alarms were unreliable. Technology has moved on three or four generations since the report was published, but public perception hasn’t yet caught up.

Zoe Forman continues, “Concerns still remain about the reliability of CO alarms despite the fact that none of the models featured in the report are available today. All products are now put through rigorous independent testing before being released into the public domain, and manufactured to the latest EN50291:2001 legislative standard - the most stringent to date. Those that meet this standard should carry a recognised international mark such as the British Kitemark, which also signifies that the manufacturing system is compliant with ISO9001 criteria. Alternative marks would include LPCB.

Safety as standard

In industrial environments, an HSE investigation will follow any serious incident involving gas poisoning, This leads to improved guidance to employers on how to avoid future incidents, and regular servicing of industrial combustion equipment is a key feature. Its estimated that around two thirds of fatal incidents would probably have been avoided if appliances had been serviced by a competent installer in the previous year. As such, CoGDEM intends to persistently campaign for employers, landlords and home owners to put in place annual safety checks as standard practice.

Said Zoe Forman, “When appliances work properly, and there is enough fresh air to allow complete combustion, the amount of CO produced is typically not dangerous. But if an appliance goes wrong, a vent gets clogged or debris blocks a chimney or flue, then fumes can’t escape and start to build up inside the premises which could result in a serious CO problem”.

“Most boiler manufacturers specify an annual service, so we deem the ideal time for a CORGI registered installer to carry that out is during a routine safety check visit. Aside from safety considerations, it also makes good economic sense to service boilers, water heaters and fires every year since this makes them more efficient, last longer and less likely to break down.”

One of CoGDEM’s other pressing aims is to lobby parliament and local government to help speed up the adoption of new regulations that insist a CO alarm is fitted in every home as standard. Stronger laws have already been introduced in ten US states to tackle CO incidents, whereby property sellers must prove appliances have been checked in the last 12 months and that there is a working CO detector fitted with an audible alarm.

The Group also aims for CO detectors to be fitted as standard in all rental properties, and to be a mandatory inclusion in building codes for new builds and renovations. In addition, COGDEM advocates that Flue Gas Analysers should always be used by competent engineers when servicing and maintaining appliances.

Measuring air quality

It is common practice to test industrial flues and chimneys using Flue Gas Analysers, but this is less common in domestic situations. To prevent household flues and chimneys blocking up, the HSE advises that they are swept regularly and checked for cracks, corrosion, holes and debris. Animals and birds can build nests in chimneys, and vibrations can shake vent pipes loose from appliances such as water heaters and gas dryers - both of which cause toxic fumes to seep back into the house. But, crucially, checking chimneys, vents and flues for CO gas requires the air to be tested as well.

A Welsh couple in their 50s are a tragic testament to this fact, having been poisoned when the chimney flue from their solid fuel stove became blocked. Installed around 2002, the stove should have been checked a year later by council officials. A combination of birds’ nests and soot gradually blocked the very unusual system of flues, which led from four fireplaces to the chimney shared with next door. The debris had been inadvertently dislodged as it was cleaned by a neighbour, and set alight by the stove causing thick, black smoke to fill the house.

Using a Flue Gas Analyser to check for CO gas movement is a potentially life saving measure. By placing the probe into a chimney or flue, it’s possible to see the levels of oxygen and CO present - as well as measure the ambient indoor air quality, in comparison to fresh clean outdoor air.

“Thanks to advances in electronics, it is now cheaper, easier - and therefore more common - for qualified and Corgi registered engineers to use Flue Gas Analysers. Analysers can be bought for as little as £150, and a simple check can be run both safely and efficiently whenever required - allowing flues, vents and appliances to be fully investigated, cleaned and retested in the event of a suspicious reading.”

Putting CO on the radar

Trying to contain carbon monoxide has remained consistently hard to achieve over the last few decades, largely due to poor control and detection methods and a growing lack of public awareness. But clear guidelines now exist for safe fuel-burning appliances and ventilation designs in industrial and domestic environments - as well as a variety of reliable detection methods and rigorous instructions for appliance installation and maintenance.

However that’s still not enough for action groups like CoGDEM. In its determination to increase awareness of the dangers and lobby for ever-more stringent safety measures, the CoGDEM task force won’t rest until every property, whether industrial or domestic, is properly protected. As Zoe Forman concludes, “If we can prevent just one needless CO poisoning incident happening, then the campaign will be a success. But if we can stop countless people being exposed to these risks on a daily basis, the message really will have hit home - and that’s what we’re hoping for. With such high quality detection solutions so readily available, and more affordable, there really is no excuse for any property to remain under threat - or for this deadly gas to ever strike again. All employers can do their bit to help their employees by publicising this danger; CoGDEM can supply leaflets to companies for them to distribute to all staff.”


1 & 2 Department of Trade and Industry, 2005, Home safety network: carbon monoxide poisoning statistics, HASS data

3 Department of Trade and Industry, 2005, Home safety network: carbon monoxide poisoning statistics, HASS data

4 Environmental Public Health, Quarterly Bulletin, research attributed to DTI, 2005

5 Environmental Public Health, Quarterly Bulletin, research attributed to HSE, 2006

7 Research conducted by The ‘Home Safety’ Report

Published: 10th Oct 2006 in Health and Safety International

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