WA Laws/Rules Regarding Smoke Detectors and Carbon Monoxide Detectors
This article explains what the Washington Home Inspector Standards of Practice (SOP) say (or don’t say) about smoke detectors and carbon monoxide detectors. It also highlights the actual legal requirements during real estate transactions—which have nothing to do with inspectors. By reading this material and checking the links, you’ll understand what’s covered in inspections, what’s required during a sale, and why you should double-check for your own safety.
Carbon monoxide detectors: Not mentioned anywhere.
Smoke detectors: The only reference is WAC 308-408C-110, which says inspectors are not required to inspect ancillary systems, “including but not limited to smoke/heat detectors.”
👉 Bottom line: Your inspector does not check these devices unless they go beyond SOP as an added service.
Separate laws cover sales and occupancy:
Smoke Alarms – Required in every residence (RCW 43.44.110 and RCW 19.27.530). Sellers must ensure devices are installed and functional before closing. Placement:
In every sleeping room
Outside each sleeping area
On each floor of the home
Carbon Monoxide Alarms – Required since 2011 (RCW 19.27.530). Must be installed in:
Any dwelling with fuel-burning appliances
Any dwelling with an attached garage
All new construction and homes being sold
Inspectors don’t cover this under SOP.
Washington law requires sellers to provide working alarms.
You should always test smoke and CO alarms yourself—your life depends on it.
Q1: Does a home inspector check smoke or carbon monoxide detectors in Washington?
No. The SOP exempts inspectors from testing or verifying them. If they do check, it’s an optional service, not a requirement.
Q2: Who is responsible for making sure detectors are in place during a home sale?
The seller. Under RCW 19.27.530, smoke and CO alarms must be installed and working before the buyer takes possession.
Q3: What happens if detectors are missing at closing?
The transaction can still close, but the seller may be in violation of state law. Often escrow companies require certification that alarms are present before funds are released.
Q4: Are battery-only smoke detectors allowed?
Yes, but Washington requires tamper-resistant, 10-year lithium batteries in many cases unless the home has hardwired alarms. Local jurisdictions may add their own rules.
Q5: Where should I install carbon monoxide detectors?
Outside sleeping areas
On each floor of the home
Near but not directly next to fuel-burning appliances
Q6: Are rentals covered by these laws too?
Yes. Landlords must install and maintain detectors. Tenants are usually responsible for replacing batteries.
Q7: What if my home doesn’t have an attached garage or gas appliances—do I still need CO detectors?
For sales and new construction: yes. For existing owner-occupied homes without a transaction, CO detectors may not be required—but installing them is still strongly recommended for safety.
Smoke alarms save lives, but only if they’re working properly. Test monthly!
The placement of smoke detectors depends on your home’s layout, HVAC systems, and size. At a minimum:
One per floor (including the basement).
One in each sleeping area (every bedroom).
One outside each sleeping area (hallway).
One near the kitchen (but never directly above the stove).
Additional alarms near fireplaces, large open areas, or other strategic locations.
👉 Always follow the manufacturer’s installation recommendations and NFPA 72 standards.
💡 Pro Tip: Err on the safe side—install alarms in every bedroom and hallway.
Monthly test: Press the test button (remembers only checks power, not smoke sensitivity).
Seasonal battery changes: Replace batteries at least once a year—many people do this twice yearly during Daylight Saving Time changes.
Use smoke spray for a realistic test of sensor function.
Replace units every 10 years (per Pittway Corp. recommendation).
Clean yearly:
Remove the unit, vacuum or use compressed air on the sensing chamber.
Wipe the outside with a damp cloth.
Reinstall and re-test.
Carbon monoxide is an odorless, tasteless, colorless toxic gas known as the “silent killer”. It interferes with your body’s ability to transport oxygen and can cause:
Headaches, dizziness, confusion, drowsiness.
Burning eyes, loss of consciousness.
Severe cases: brain damage or death.
Children, seniors, and those with heart or lung conditions are at higher risk.
Appliances and equipment that burn charcoal, gasoline, kerosene, wood, propane, natural gas, or heating oil:
Furnaces, stoves, fireplaces, hot water heaters.
Gas dryers, grills, room heaters, vehicles in garages.
Unlike smoke, CO mixes evenly in air.
Best height: Install at knee-level (sleeping person’s nose/mouth height).
If pets/children may tamper, install at chest height.
Avoid blocking detectors with curtains, furniture, or objects.
Monthly testing recommended.
Strategic placement:
Near all bedrooms.
On every level of the home.
In the basement (especially if furnace is there).
In the laundry room (if gas dryer).
In the garage (if vehicles are parked inside).
In any room with a solid fuel-fired appliance.
⚠️ Avoid combo smoke/CO alarms unless selling your home—separate units work better.
RCW 29-3-16a requires:
Smoke detectors in the immediate vicinity of each sleeping area in one- and two-family dwellings and manufactured homes.
Detectors must comply with NFPA 72 standards.
Owners must provide, install, and replace smoke detectors.
Tenants must perform routine maintenance if the unit is not owner-occupied.
✅ Bottom Line:
Smoke alarms high (ceiling/wall).
CO alarms low (knee/chest height).
Test monthly, change batteries at least once a year, replace alarms every 10 years, and clean annually.
Follow Washington law and NFPA standards.
Q: Where should I install a carbon monoxide detector in my home?
A: Place CO detectors near all bedrooms, on every level of your home, and close to fuel-burning appliances such as furnaces, water heaters, fireplaces, or gas dryers. Basements and attached garages should also have CO alarms.
Q: How high should carbon monoxide detectors be installed?
A: CO mixes evenly with air, so detectors work best at knee height (the level of a sleeping person’s nose and mouth). If children or pets may tamper with them, install at chest height.
Q: Do I need a CO detector in every bedroom?
A: Ideally, yes. At minimum, you should install one CO detector outside each sleeping area so the alarm is heard at night. For maximum protection, install one inside every bedroom.
Q: Can I use a combination smoke and CO alarm?
A: Combination units are available, but separate alarms are generally recommended since smoke rises and CO mixes with air. If you do use a combo unit, install it on the ceiling for smoke detection.
Q: How often should I test my CO detector?
A: Test monthly using the test button. Replace the batteries at least once a year (many people do it during Daylight Saving Time changes).
Q: How long do CO detectors last?
A: Most CO detectors have a lifespan of 5–7 years. Always check your manufacturer’s recommendations and replace the unit when it reaches end of life.
Q: What are the symptoms of carbon monoxide poisoning?
A: Early symptoms include headache, dizziness, confusion, fatigue, and nausea. Prolonged exposure can cause unconsciousness, brain damage, or death. Children, seniors, and people with heart or lung conditions are more vulnerable.
Q: If my CO alarm goes off, what should I do?
A: Leave the home immediately, call 911 or your local fire department, and do not re-enter until professionals confirm it is safe. Have appliances inspected before using them again.