Ontario Fire Code requires all homes (whether single family, semi, or other) with fuel burning appliances (including fireplaces) and/or attached garages, to be equipped with CO alarms. These alarms should be located outside of all sleeping areas.
Do you live in a condo or apartment building? If it has a service room, CO alarms must be installed in the service room and adjacent to each sleeping area above, below and beside the service room. If it has a garage, CO alarms must be installed adjacent to each sleeping area of all units above, below and beside the garage.
The only residences not affected by the regulation are those that are all electric and have no attached garages or fireplaces. But if there is outside equipment, such as large generators or machinery, that vents outside your windows or doors, you may also wish to consider installing a CO alarm in your home to further protect your safety.