Expired Smoke and CO Alarms:
Why the Age of Your Detector Actually Matters
Expired smoke and carbon monoxide alarms are one of the most common safety findings on any inspection report. They also tend to get dismissed. Here is why that is a mistake, and what to do about it before move-in.
Walk through almost any home that has been on the market for a few years and you will find at least one smoke detector that has yellowed on the ceiling, is making occasional chirping sounds, or has been disconnected entirely by the previous occupant trying to stop the chirping. Carbon monoxide detectors fare no better.
Expired alarms are one of the most common safety findings on inspection reports, and they are also among the most actionable. The fix is inexpensive and straightforward. Here is why it matters and how to do it right.
Why Detectors Have an Expiration Date
Both smoke detectors and carbon monoxide detectors have internal sensing components that degrade over time. This is not a marketing strategy by manufacturers. It is a physical reality of how the sensors work.
Smoke detectors use one of two sensing technologies. Ionization detectors use a small amount of radioactive material to ionize air between two plates, which creates a current. Smoke disrupts that current and triggers the alarm. Photoelectric detectors use a light beam and sensor: smoke scatters the light into the sensor, triggering the alarm. In both cases, the sensing components become less reliable as they age. Dust accumulation, humidity cycling, and simple material degradation all contribute.
Carbon monoxide detectors use electrochemical sensors that react to CO molecules. Those sensors have a finite lifespan because the chemical reaction that enables detection is consumptive: the sensor gradually becomes depleted even without any CO exposure. A CO detector that has exceeded its service life may not detect CO at levels that are harmful.
10 Years: Smoke Detector
The National Fire Protection Association recommends replacing smoke detectors every 10 years from the manufacture date, regardless of whether the unit tests correctly with the button. The sensing chamber degrades over time independently of battery function.
5-10 Years: CO Detector
Carbon monoxide detectors often have a shorter service life because the electrochemical sensor depletes over time. Depending on the model, manufacturers rate them for roughly 5 to 10 years, and many current units sound an end-of-life warning. Check the manufacture date label on the back of the unit.
Oregon and Washington Requirements
Both Oregon and Washington have specific requirements for smoke and CO alarms that apply at the time of a home sale.
Oregon law requires working smoke alarms on every level of the home and outside each sleeping area, plus alarms inside bedrooms where the building code in effect when the home was built or remodeled required them. CO alarms are required at sale when the home has a CO source (any fuel-burning appliance, fireplace, or attached garage), and in homes built in 2011 or later regardless. They go on each level with bedrooms, inside each bedroom or within 15 feet outside each bedroom door. The seller is responsible for having the alarms in place at sale.
Washington requires sellers of owner-occupied single-family homes to provide smoke detection and to equip the home with CO alarms, installed per the state building code, before the buyer occupies it.
Beyond the legal minimums, the operational question matters more: an alarm that is technically present but has a 14-year-old sensing chamber may pass a basic test while providing significantly degraded protection.
Where Alarms Need to Be
| Location | Smoke Alarm | CO Alarm |
|---|---|---|
| Inside each bedroom | Required in newer homes; older homes follow the code in effect when built | Oregon allows it inside the bedroom instead of outside the door |
| Outside sleeping areas | Required in both states | Required near bedrooms when the home has a CO source (Oregon: within 15 ft of each bedroom door) |
| Each level | Required, including basements | Oregon: each level with bedrooms. Washington: each level |
| Attached garage | Not required inside the garage | Not inside the garage; an attached garage counts as a CO source |
| Kitchen | At least 10 ft from cooking appliances (6 ft for photoelectric) | Follow the manufacturer’s placement instructions |
How to Handle This Finding Practically
Expired alarms are the most affordable safety upgrade a homeowner can make. A combination smoke and CO detector from a reputable brand typically costs $20 to $50 per unit. For a 3-bedroom home, fully replacing every detector runs $100 to $250 in parts alone, plus an hour of work to swap them.
Several things make this worth doing at move-in rather than deferring:
- You have an opportunity to confirm correct placement in every required location, not just assume the previous owner had it right.
- You start your ownership with a known manufacture date, so you know exactly when replacements are due.
- Ten-year sealed-battery models eliminate the need for annual battery replacement and reduce the likelihood of a future occupant disconnecting a chirping alarm.
- For a home that has a gas furnace, gas water heater, or attached garage, properly placed and functional CO alarms are not optional safety equipment.
See our FAQ page for more on life safety findings, or visit our pricing page for home inspection costs in Portland and Oregon City.
Expired Smoke and CO Alarms FAQ
