The Essential Guide for Homeowners: Smoke and CO Detectors

Smoke detectors and carbon monoxide (CO) detectors are designed to provide early warnings in the event of fire or dangerous CO levels, giving you and your family valuable time to evacuate and seek help. Understanding the different types of these detectors, their optimal placement, and maintenance requirements can help ensure their effectiveness.

First up: smoke detector types

There are two basic types of smoke detectors, ionization and photoelectric smoke detectors. It's important to know which you have. Each type operates differently and detects different types of fires. 

🔥Ionization Smoke Detectors contain a small amount of radioactive material between two electrically charged plates, which ionizes the air and creates a current. When smoke enters the chamber, it disrupts the current, triggering the alarm. They are best for detecting fast-flaming fires.  The advantage to this type of detector is its ability to provide a quick response to fast, flaming fires. These may be quite a bit less effective at detecting slow, smoldering fires early though. 

☁️ Photoelectric Smoke Detectors use a light source aimed away from a sensor. When smoke enters the chamber, it scatters the light towards the sensor, triggering the alarm. They work well detecting slow, smoldering fires but may be slightly slower in detecting fast-flaming fires. 

Which one do I have? You can usually identify the type of smoke detector you have by examining the unit itself. Here are some steps to help you determine the type of smoke detector in your home: Check the Label: Most smoke detectors have a label or sticker on the back or inside the battery compartment that provides information about the detector. Look for key terms: The inside of the battery compartment may indicate "Ionization," or "Photoelectric". You can also check the back of the unit.  Inspect the Chamber:  If you can safely open the detector, you may be able to see the sensor mechanism. Ionization Detectors usually have a small metal chamber with a radioactive material warning symbol. Photoelectric Detectors typically have a light-emitting diode (LED) and a light sensor. Consult manufacturer’s documentation or perform a model number search: Manuals, user guides, or other documentation that came with device should specify the type of detector. If you no longer have the manual, you might find a PDF version on the manufacturer’s website using the model number. You can also check online by model number at the manufacturer's website.

Which one is best?

Your best choice? Both. As you can see, each type of detector is designed to provide an early warning of quite different types of fires. If you have one type, consider complementing it with the other and have at least one of each type on each floor. If you are replacing a detector, consider a dual-type detector that features the benefits of both ionization and photoelectric detectors.  

Do I also need Carbon Monoxide (CO) detectors? 

Carbon Monoxide (CO) detectors are essential for health. Unlike smoke, which you can see and smell, carbon monoxide is invisible and cannot be detected by human senses. This makes it extremely dangerous because you won't know it's there until it's too late. 

Health risks include acute poisoning that start with symptoms like headache, dizziness, and confusion, and can get much worse. Chronic exposure to low levels of CO are equally hazardous and may go undetected due to their confusion with other illnesses. 

CO can be the result of faulty appliances, blocked vents, and other sources. In many cases, CO is required for new construction, but even where not mandated, CO detectors are critically important 

Placement of smoke and CO detectors Smoke and CO detectors should be installed on every level of the home, including the basement as well as inside and outside each sleeping area. They should be mounted on the ceiling or high on the wall - remember smoke rises. Avoid placing CO detectors within 15 feet of cooking or heating appliances to prevent false alarms.

Maintaining your detectors There are three steps involved in maintaining your detectors:  Monthly Testing: Test your smoke and CO detectors monthly to ensure they are functioning correctly. Battery Changes: Change the batteries every six months, even if the detector is hardwired with a battery backup. In some cases sealed units do not require battery changes over the (typically 10-year) life of the unit.  Replacement: Most smoke detectors are designed to last up to 10 years, whereas CO detectors typically every 5-7 years, as the sensors can degrade over time. In all cases, follow the manufacturer’s instructions.

Changing your detectors

If your detector is expired (typically 10 years for smoke detectors and 7 years for CO detectors - check your specific device), you can usually perform the replacement yourself. This even goes for interconnected detectors, but if you are unsure, call a professional. Your local county or city might also have help available in terms of guidance. Note that many newer smoke detectors are dual-sensor, and some even integrate CO detection as well.