Carbon Monoxide :

Indoor Air Quality

Nowadays most people are aware of the damage that outdoor air pollution can do to their health but many do not know that indoor air pollution can also have significant health effects. In this project we are going to show that indoor air quality should be associated not only with the health and comfort in our homes but also with safety. Low levels of any pollutant in the house could be as damaging in the long term as high levels. Here we are going to justify are concerns and present our solution.

Carbon Monoxide (CO)

Introduction

Carbon monoxide poisoning has haunted mankind since the discovery of fire and remains the most common cause of death due to poisoning. As evidence, hundreds of papers in the contemporary medical literature describe the effects of carbon monoxide poisoning and debate the methods of treatment. Additionally, further debate centres on the usefulness of the consumer carbon monoxide alarms, appropriate response protocols and problem remediation. Not under debate, however, are the dramatic and tragic effects that we often read in the headlines.

What is Carbon monoxide?

Carbon monoxide is a colourless, odourless, tasteless, non-irritating, and poisonous gas produced when carbon-based fuels burn incompletely. Complete combustion of carbon and oxygen produces carbon dioxide (C02), a non-toxic gas. Incomplete combustion occurs when there is insufficient combustion air, insufficient time for complete combustion, incomplete mixing of air and fuel, or when the temperature drops below combustion temperature. CO is slightly lighter than air (0.97) and easily moves through small cracks throughout an entire house.

Sources of Carbon monoxide

Seven out of eight homes contain some threat of carbon monoxide poisoning. The following is a list of potential sources of carbon monoxide in the home:

What signs can you look out for?

• Yellow or brown staining around or on appliances
• Pilot lights frequently blow out
• Increased condensation inside windows
• Yellow rather than blue flame

What are the causes of Carbon monoxide poisoning?

Both old and new homes alike contain the sources that could cause CO poisoning. Older homes are susceptible because of malfunctioning appliances and faulty ventilation. However, new homes that are energy-wise and tightly sealed to trap heat may be at even more risk. Gas, oil and other fuel furnaces, gas-powered appliances, fireplaces and wood stoves all require oxygen to operate efficiently. If the home is too airtight, these devices may begin competing for the available oxygen. They may cause "backdrafting" which pulls polluted or CO contaminated air back into the home.

In simple terms you are at risk for CO poisoning if:

• your appliance was poorly installed
• your appliance is not working properly
• your appliance has not been checked for safety or maintained regularly
• there is not enough fresh air in the room
• your chimney or flue gets blocked up
• you allow unqualified people to install or maintain your appliance

What are the health effects of Carbon Monoxide?

When you breathe air containing carbon monoxide, it is absorbed through the bloodstream where it displaces oxygen and bonds with the haemoglobin in your blood. Carbon monoxide has a greater affinity to haemoglobin than oxygen; CO bonds to haemoglobin about 250 times better than oxygen. Without oxygen, vital organs, your heart and brain become deprived and will begin to deteriorate. To compensate, your heart rate increases, breathing may become difficult and in the most serious circumstances cardiac trauma, brain damage, coma and even death will result.

Carbon monoxide is an extremely dangerous poison because it can not be seen smelled or tasted. The early symptoms are similar to the flu. Because CO reduces oxygen delivery to the brain, persons with elevated levels of CO in their blood do not think; clearly, and might not recognise the warning.

Symptoms of CO poisoning

The classic symptoms associated with CO poisoning are directly attributable to its ability to produce tissue hypoxia (suffocation) and be directly poisonous to cells. Therefore, organs which are the most sensitive to tissue suffocation will be affected most significantly - the nervous (brain) and cardio-vascular systems (heart).

At moderate levels, you or your family can get severe headaches, become dizzy, mentally confused, nauseated, or faint. You can have memory loss, permanent brain damage or even die if these levels persist for a long time. Low levels can cause shortness of breath, mild nausea, and mild headaches, and may have longer-term effects on your health. Since many of these symptoms are similar to those of the flu, food poisoning, or other illnesses, you may not think that CO poisoning could be the cause.

In conclusion the symptoms to look for are:

• Fatigue
• Headaches
• Flu-like symptoms such as nausea
• Chest pains
• Sudden giddiness when standing up
• Sickness, diarrhoea and stomach pains
• Erratic behaviour

Figure 1. Progressive CO poisoning symptoms
The data in this figure were obtained from the Toronto Hospital and the Occupational Safety and Health Association.

Delayed Neurological Effects

In treated patients with minimal exposures, the symptoms resolve after several hours. Even in severe cases that have been successfully treated. there is general resolution of the symptoms and apparent recovery. Unfortunately, some patients regress and develop delayed neurological sequelae or delayed, subsequent effects. This delayed syndrome is reported in 2 - 12% of CO poisoned patients. The onset may rapidly occur (within two days of the apparent recovery) or may be delayed for four to six weeks.

The most prevalent symptoms include mental deterioration, fecal and/or urinary incontinence and gait (ability to walk) disturbances. Common aspects of mental deterioration include persistent headaches, personality changes, confusion, memory loss, and irritability. Long-term follow up in one series of patients revealed a 75% recovery rate after two years, but another study reported that 11% displayed gross neuropsychiatric damage, 33% had personality deterioration, and 43% suffered memory loss when they were re-evaluated three years after the poisoning incident.

It is not possible to predict who will develop delayed effects. Although problems may develop in patients who have had only mild to moderate toxic levels in their systems, there is a tendency for it to occur with greater frequency in those patients who have had prolonged episodes of unconsciousness. A Parkinson's Disease-like syndrome has also been associated with CO poisoning. These persistent effects of CO are not generally appreciated and present a significant personal and financial dilemma for those affected.

High risk groups

Children are at greater risk to experience nervous system symptoms at lower levels due to their inherently higher metabolism. The incidence of delayed neurologic sequelae has been reported to be as high as 11% in children. Adults with pre-existing heart disease may develop associated problems, such as angina, at significantly lower levels than healthy adults, placing them at greater risk for a heart attack. Smoke inhalation victims may become comatose at seemingly mild toxic levels of carbon monoxide, due to the inhalation of other toxic by-products of combustion such as cyanide that produces similar cellular suffocation. Pregnant females who are exposed to CO pose a significant risk to the foetus as the recovery half-life is significantly increased due to foetal to maternal blood transport complications.

Other high-risk groups, which are particularly sensitive to the effects of CO, because of various organ impairments, are:

• those whose oxygen carrying capacity is decreased due to anaemia or other haemoglobin disorders;
• those with increased oxygen needs such as those encountered in fever and hyperthyroidism;
• those with systemic hypoxia due to respiratory insufficiency;

Advice from the Health and Safety Executive

If you think your appliance is spilling CO or you feel you have the above symptoms

• Switch off the appliance - do not reuse until remedial action has been taken
• Open doors and windows to ventilate the room - do not sleep in it
• Visit your GP urgently and inform them that you believe these symptoms may be related to CO. They will be able to tell by means of a blood test
• Call a CORGI registered installer

If you are concerned about gas safety you can ring

• HSE Gas Safety Advice Line 0800 300 363
• Transco Gas Leak 0800 111 999
• CO Support (Mon -Thur 9 am - 3 pm) 0113 2605112

Types of CO detection technology

The three most common CO detection technologies available today are: chem-optical (gel cell), electro-chemical and semiconductor.

1) CHEM-OPTICAL (GEL CELL) TECHNOLOGY

Chem-optical technology alarms are also known as gel cell or biomimetic technology alarms. These alarms utilize a type of sensor that simulates hemoglobin in the blood.

2) ELECTRO-CHEMICAL

Electro-chemical technology alarms are usually battery powered. This type of sensor typically has a limited lifetime of about 2 - 5 years. Some manufacturers' models will require its battery and/or sensor to be changed periodically by installing an expensive replacement. Other manufacturers' models have sealed housing that requires the entire unit to be discarded once the battery power supply is depleted.

3) SEMICONDUCTOR TECHNOLOGY

There are a variety of CO alarms that utilise semiconductor or tin dioxide technology available on the market today. Unlike alarms, which utilise chem-optical or electro-chemical technology, semiconductor detectors do not require expensive replacement sensors. However, not all semiconductor CO alarms are alike. Some manufacturers utilise semiconductor sensors that are not designed to be used in a CO specific alarm and may be prone to false and/or nuisance alarms.

Where should the alarm be sited?

The following guidelines were taken from the British Standard Institute (BSI) and follow the standard BS EN 50292:2002 with title "Electrical apparatus for the detection of carbon monoxide in domestic premises. Guide on the selection, installation, use and maintenance". They should be followed in order to minimise the risk of misleading indications.

Which room?

Ideally, a sensor should be installed in every room containing a fuel burning appliance. Additional sensors may be installed to ensure that adequate warning is given for occupants in other rooms, by locating sensors in:

• remote rooms in which the occupant(s) spend considerable time whilst awake and from which they may not be able hear an alarm from sensors in another part of the premises,and
• every sleeping room.

Where not to install the sensors

The sensors should not be installed:

• in an enclosed space (for example in a cupboard or behind a curtain);
• where it can be obstructed (for example by furniture);
• directly above a sink;
• next to a door or window;
• next to an extractor fan;
• next to an air vent or other similar ventilation openings;
• in an area where the temperature may drop below - 10 o C or exceed 40 o C, unless it is designed to do so;
• where dirt and dust may block the sensor;
• in a damp or humid location;
• in the immediate vicinity of the cooking appliance.

Sensors located in the same room as a fuel-burning appliance

If the sensor is located on a wall:

• it should be located close to the ceiling;
• it should be located at a height greater than the height of any door or window.

A ceiling mounted sensor should be at least 300 mm from any wall, and for a wall mounted sensors it should be at least 150 mm from the ceiling. The sensor should be at a horizontal distance of between 1 m and 3 m from the potential source. If there is a partition in a room, the sensor should be located on the same side of the partition as the potential source. Carbon Monoxide alarms in rooms with sloped ceilings should be located at the high side of the room.

Sensors located in sleeping rooms and in rooms remote from a fuel burning appliance

Sensors located in sleeping rooms and in rooms remote from the fuel-burning appliance should be located relatively close to the breathing zone of the occupants.

Legislation

According to the BSI (BS EN 50291:2001) alarm indicators and audible alarms shall operate simultaneously at the set points as listed in Table 1.

Table 1 - Alarm conditions

Once activated, the alarm shall remain in operation at carbon monoxide concentrations above 50 ppm.