CO2 alarm ?
Do you drink a lot of fizzy drinks .
Good point. Should have said CO (Carbon Monoxide) which is the result of oxygen-starved combustion in improperly ventilated fuel-burning appliances such as oil and gas furnaces, gas water heaters, gas ovens, gas or kerosene space heaters, fire places and wood stoves.
So to add to my original question - how many of you have smoke and CO alarms, either combined or separate. The following from
Smoke Alarms « UK Fire Service Resources
There are mainly four types of smoke alarm currently on the market – ionisation, optical (also described as photo electronic), heat and combined.
Ionisation: These are the cheapest and cost very little to purchase. They are very sensitive to small particles of smoke produced by fast flaming fires, such as paper and wood, and will detect this type of fire before the smoke gets too thick. They are marginally less sensitive to slow burning and smouldering fires which give off larger quantities of smoke before flaming occurs. They can also be too over-sensitive near kitchens.
Optical: These are more expensive but more effective at detecting larger particles of smoke produced by slow-burning fires, such as smouldering foam-filled upholstery and overheated PVC wiring. They are marginally less sensitive to fast flaming fires. Optical alarms can be installed near (not in) kitchens, as they are less likely than ionisation alarms to go off when toast is burned.
Heat Alarms: They detect the increase in temperature from a fire and are insensitive to smoke. They can therefore be installed in kitchens. They only cover a relatively small area of a room, so potentially several heat alarms need to be installed in a large kitchen.
Combined Optical Smoke and Heat Alarms: Combinations of optical and heat alarms in one unit to reduce false alarms while increasing the speed of detection, a technology also called Thermoptek sensor technology.
Combined Smoke and Carbon Monoxide Alarms: Alarms that combine both smoke detection and CO alarm protection in one ceiling-mounted unit. This reduces costs and takes up less of your living space.