Smoke and carbon monoxide detectors are two of the simplest devices in your home, but they protect against two of the most dangerous threats: fire and invisible toxic gas.
Fires can spread fast. Carbon monoxide can build up silently with no smell, no color, and no warning signs until symptoms start. In both cases, early detection is what gives you time to react.
This guide will help you understand:
- The difference between smoke and carbon monoxide detectors
- Where they should generally be installed
- The main types available today
- How long they last and how to maintain them
- When DIY makes sense and when to hire a professional
The recommendations here apply broadly across the United States and align with common national safety standards. If you’re in Northeast Ohio, we also offer professional smoke and CO detector installation and can handle assessment, product selection, and installation for you.
Smoke vs. Carbon Monoxide: What Each Detector Actually Does
What Smoke Detectors Do
Smoke detectors are designed to sense smoke particles in the air. When smoke reaches a certain concentration, the alarm sounds to alert you.
They are meant to:
- Detect developing fires early
- Wake sleeping occupants
- Provide time to exit the home safely
They do not detect gas leaks. They do not detect carbon monoxide.
What Carbon Monoxide Detectors Do
Carbon monoxide (CO) detectors monitor the air for carbon monoxide gas. CO is produced when fuel does not burn completely. Common sources include:
- Gas furnaces
- Water heaters
- Gas stoves
- Fireplaces
- Attached garages
- Generators
Carbon monoxide is colorless, odorless, and tasteless. You cannot detect it without a device.
Symptoms of Carbon Monoxide Exposure
Low-level CO exposure can feel like the flu: headache, dizziness, nausea, fatigue. Higher exposure can lead to confusion, loss of consciousness, and death.
Smoke alarms alone are not enough. Most homes in the U.S. should have both smoke and carbon monoxide coverage.
Where Detectors Should Go (High-Level Overview)
Proper placement matters just as much as having the devices.
Smoke Detector Basics
In general, smoke detectors should be installed inside every bedroom, outside sleeping areas (such as hallways), on every level of the home, and in the basement. Many homes are under-protected, especially in hallways outside bedrooms.
For full room-by-room recommendations, see our complete guide on where to install smoke detectors for detailed placement instructions.
Carbon Monoxide Detector Basics
CO detectors are typically installed near sleeping areas, on each level of the home, near but not directly next to fuel-burning appliances, and near attached garages (but not inside them). Incorrect placement is common, especially installing them too close to furnaces or too far from sleeping areas.
For specific location guidance, see our complete guide on where to install carbon monoxide detectors.
Types of Smoke Detectors (Overview)
There are several types of smoke detectors, each designed to respond differently to fire conditions.
Ionization Smoke Detectors
- More responsive to fast-flaming fires
- Typically lower cost
- Can be more prone to nuisance alarms near kitchens
Photoelectric Smoke Detectors
- Better at detecting slow, smoldering fires
- Less prone to false alarms near kitchens and bathrooms
- Commonly recommended for hallway placement
Dual-Sensor Smoke Detectors
- Combine ionization and photoelectric technologies
- Broader detection capability
- Higher cost but more comprehensive
Combination Smoke/CO Units
- Detect both smoke and carbon monoxide
- Good for bedrooms or hallway locations
- Reduce the number of devices on ceilings
Smart Smoke Alarms
- Connect to Wi-Fi
- Send phone alerts
- Can integrate with smart home systems
Power Options
Smoke and CO detectors are available in replaceable battery models, 10-year sealed battery models, hardwired units with battery backup, and interconnected systems (wired or wireless).
We break down each smoke detector type and when to use it in our smoke detector types guide.
If you’re deciding between plug-in, battery, hardwired, and combo CO units, see our CO detector types guide.
Lifespan, Testing, and Replacement Basics
Detectors do not last forever.
Typical Lifespan
- Smoke alarms: about 10 years
- CO alarms: often 5 to 7 years
Even if they “still work,” sensors degrade over time.
How Often to Test
- Test monthly using the built-in test button
- Test after battery replacement
- Test after any electrical work
Cleaning
Dust and cobwebs can interfere with sensors. Vacuum vents periodically, wipe exterior surfaces, and avoid spraying cleaners directly into units.
End-of-Life vs Low-Battery Chirps
Low-battery chirps typically occur once per minute. End-of-life chirps often follow a consistent pattern every 30–60 seconds and continue even after battery changes. Check the manufacturing date on the back of the unit. If it is near or beyond the rated lifespan, replace the entire device.
For a detailed schedule and troubleshooting guide, see our article on how to test, clean, and replace smoke and CO detectors.
10-Year Sealed Battery Detectors
These units use a sealed lithium battery designed to last the full life of the alarm, typically 10 years. You replace the whole unit at end of life rather than swapping batteries annually.
Pros
- No annual battery changes
- Less tampering in rentals
- Fewer middle-of-the-night battery chirps
- Convenient for high ceilings
Cons
- Entire unit must be replaced at end of life
- Still require monthly testing
- Higher upfront cost
We have a dedicated deep-dive article comparing 10-year sealed battery alarms to standard battery models, including product recommendations.
DIY vs Professional Installation
Some situations are straightforward. Others are not.
When DIY Is Usually Fine
- Replacing a basic battery-powered unit
- Swapping like-for-like detectors
- Installing plug-in CO units
If you can safely access the location and are not modifying wiring, DIY can make sense.
When a Professional Is Strongly Recommended
- Hardwired replacements
- Adding new wiring
- Interconnected systems
- High ceilings or stairwells
- Rental properties
- Home sales requiring proper documentation
If you’re in Northeast Ohio, we can assess your current setup, supply the right detectors, install them in correct locations, and test everything in one visit.
For more detail, see our full guide on DIY vs professional smoke and CO detector installation.
What to Expect From a Professional Installation Visit
A typical professional visit includes:
- Assessment of existing detectors and coverage
- Count and placement plan based on layout
- Device selection appropriate for your home
- Installation (battery, plug-in, or hardwired)
- Full testing and verification
- Homeowner walkthrough and education
For a typical single-family home, expect about 60 to 120 minutes depending on the number of devices and system type.
Next Steps
If you want to DIY:
- Read our detailed smoke detector placement guide
- Review our CO detector placement guide
- Compare types in our smoke detector types guide and CO detector types guide
- Choose devices appropriate for your home layout
If you want professional help:
- Nationwide: search for a reputable local electrician or home safety installer.
- Northeast Ohio: visit our Smoke & CO Detector Installation page or contact us directly for a quote.
At minimum, do this today: check the manufacturing date on every smoke and CO detector in your home, test each one, and replace any unit nearing or past its lifespan.
These small devices do a big job. Making sure they are the right type, in the right location, and within their service life is one of the simplest ways to protect your home and family.