If your home was built after 1986, it will have at least one hard wired smoke alarm connected directly to your electrical panel. It is not acceptable to replace a hard wired alarm with one that is battery operated. A home must maintain at least the same level of protection as originally required. It is the law.
If the number and placement of smoke detectors in your home is already correct but you need carbon monoxide protection to meet the requirements of the Orillia Bylaw regarding CO protection, combination smoke and CO units are a good choice to avoid having your ceiling dotted excessively with devices.
If you are missing protection on a particular level or a sleeping area, you might want to consider the ONELINK alarms that allow you to stay linked to your existing system without having to run additional wires. With the average maximum escape time now estimated at 3 minutes, it is wise to consider keeping your alarms all interconnected so that when one rings, they all ring.
Carbon monoxide is an extremely poisonous gas. It is especially dangerous because you cannot see or smell its presence. Municipalities like Orillia that require these upgrades are to be commended for looking after the well-being of their citizens.