Carbon Monoxide is a colorless, oderless and tasteless gas that it also extremely toxic. It is product of combustion and is present in buildings with fireplaces and gas fired appliances like furnaces and water heaters. Typically it is vented from the building and is not a danger to the occupants. However in cases where a vent gets blocked or the appliance fails the fumes may be vented into the building.
Mild cases of carbon monoxide poisoning may manifest themselves with headaches, vertigo and flu like effects. Severe poisoning can can cause damage to the nervous system and even death.
Thankfully there are detectors that can be installed in buildings to monitor the CO levels and warn if they become dangerous. I’ve seen them in two varieties, one that can be plugged into an outlet and one that can replace a hard wired smoke detector and function as a combination unit.
I would recommend in new construction that you make the minor upgrade to a hard wired detector that monitors smoke and carbon monoxide. It is only a $15-20 upgrade on each unit. If it is existing construction then it is smart to replace or supplement your smoke detectors outside the sleeping areas and near gas fired appliances. The hard wired smoke/CO detectors run about $60.
This post has a particularly personal message to it. Last Thursday on of my best friends nearly lost his family to carbon monoxide poisoning in their home. Had it not been for an extremely fortunate set of events things might have turned out very differently. Thankfully after a night in the hospital they are making a full recovery.
In the end they discovered that the roofer who had just finished replacing the roof covered the vent which pushed the fumes into the house.