8) How important is it to measure CO ?

The concentration of carbon monoxide is an essential part of determining optimum boiler efficiency. An operation near trace levels about 100 ppm and a slight amount of excess air indicates conditions near optimum. No burner is able to mix fuel and air perfectly. The consequence is that there will be products of incomplete combustion present. Where CO begins to be produced in volume, maximum efficiency is achieved. By providing continuous monitoring of CO and O₂ flue gas analyzers make it easy to determine maximum efficiency and optimum boiler operation. In addition, keeping the level of carbon monoxide in the flue gas low will prevent leaks to the surroundings.

It is also possible to measure the level of ambient carbon monoxide with many flue gas analyzers. The exact method will be found in the operating manual. Generally a level of less than 20 ppm is to be expected in any area where people are regularly. Although the safety limits are considerably higher, thought must be given to the source of the carbon monoxide at this level. Ambient outside levels are very much lower, so it must be the result of some process. If it is leakage from a combustion system, then the chances are very high that the problems will get worse, not better. It is then essential to check the integrity of the flue system and to ensure that the draught in the flue is sufficient to exhaust all the waste gases efficiently. A blockage of the flue will have this effect, for instance. Rust may occur on the flue pipe, particularly if it is only in use for a limited time every year and operates at a lower temperature, allowing condensation to form inside the pipe. This is a typical problem for gas fired systems that are used to cover peak loads. They often never operate for long enough to reach the full temperature, allowing acidic condensation to pool.

Carbon monoxide is poisonous because CO robs your blood of oxygen. When you inhale carbon monoxide, it bonds with the haemoglobin in your blood, displacing life-giving oxygen. This produces a toxic compound in your blood called "Carboxyhaemoglobin" (COHb). Over time, exposure to CO can make you sick. Victims exposed to enough carbon monoxide can suffer brain damage, or even die.

One of the long-term exposure limits is set at 9 ppm with a maximum of 35 ppm for one hour. These low concentrations show just how dangerous carbon monoxide really is.

According to the Journal of the American Medical Association (JAMA), 1500 people die each year because of CO poisoning, and another 10,000 become ill. Since you can't see, smell, or taste carbon monoxide, it can make you sick before you even know it's there.

Carbon monoxide becomes particularly dangerous when problems with the draught regulation occur. As stated above, blockages of the flue channel, or poor design can lead to downdraughts, which can also occur as a result of later building work. One of the worst sources of carbon monoxide is to be found in the open fireplace that is allowed to die down overnight. Cooling reduces the draught in the chimney greatly, and the dying fire will tend to produce large quantities of carbon monoxide, partly due to the reduced draught, but also becouase the colder wood or coal is no longer burning efficiently.

In the framework of gas analysis, the main reasons for measuring carbon monoxide are compliance with regulations and the efficiency of combustion. Carbon monoxide is a loss of possible heating value from the material being used as fuel. It is not just an unnececessary load on the environment, it is a cost factor that should not be ignored.