Smoke & CO Detector Replacement
Handis smoke and CO detector replacement is the residential service that swaps battery-powered and 10-year sealed-lithium smoke and combination smoke/CO detectors per NFPA 72 placement — one on every level, one inside every bedroom, one outside every sleeping area, CO within 10 feet of every sleeping-area door — from $120 per unit to $350 for a six-unit whole-home swap. A smoke detector that chirps once a month for a year, gets the battery pulled, and never goes back up is one of the most common silent hazards in a house. Smoke detectors expire 10 years from the manufacture date stamped on the back; CO detectors expire at 5 to 7 years. We read the manufacture date on every existing detector before we leave. Hardwired interconnect systems on a new circuit are electrician work and route to a licensed Washington L&I contractor.
Service
What Does Smoke and CO Detector Replacement Include?
Smoke and CO detector replacement is one service with two key activities — read the manufacture date on every existing unit (the small label on the back), then replace what is past due per NFPA 72. We carry battery-powered units, 10-year sealed-lithium units (set-and-forget for the decade), and combination smoke/CO units in the truck, and walk the house against the NFPA 72 minimum (one alarm per level, one inside every bedroom, one outside every sleeping area, CO within 10 feet of sleeping-area doors). Most homes have at least one missing location, typically a CO alarm outside a basement bedroom or a smoke alarm in the basement itself.
Single Detector Replacement
Battery or 10-year sealed-lithium, smoke-only or combination smoke/CO. We pull the old unit (read the manufacture date for the record), confirm the mounting base is in good shape (or swap it if not), and install the new unit. About 15 minutes per detector. For a single unit, the visit minimum applies.
Whole-Home Detector Audit and Swap
The standard service for any home over five years old. We walk the house, count detectors, read the manufacture date on every unit, identify any NFPA 72 placement gaps, and replace what is past due plus add what is missing. Most homes need 4 to 7 units total. The whole-home audit is 30 minutes, the swaps are 10 to 15 minutes per unit. About 90 minutes to 2 hours for a typical home.
Sealed-Lithium 10-Year Upgrade
The 2010s and 2020s update — sealed-lithium detectors have a non-replaceable battery rated for the 10-year service life of the detector itself. No more changing batteries twice a year, no more 3 a.m. chirps. At year 10 the entire unit gets replaced as a single piece. We default to sealed-lithium for new installs unless you specifically want battery-replaceable units (some homeowners prefer to be able to silence a false alarm by pulling the battery — sealed units have a hush button instead).
Combination Smoke / CO Units
A single unit that detects both smoke (photoelectric or dual-sensor) and carbon monoxide. NFPA 72 requires CO detection within 10 feet of every sleeping-area door, and a combination unit covers both requirements in one wall or ceiling location. The combo unit has a separate CO sensor that expires at 5 to 7 years (per the manufacturer), so the unit itself often gets replaced before the smoke side reaches its 10-year mark. We will tell you on install which sensor is the limiting factor.
Placement per NFPA 72
The full NFPA 72 minimum: one smoke alarm on every level of the home including the basement; one inside every bedroom; one outside every sleeping area (in a central hallway); CO alarms within 10 feet of every sleeping-area door. Mounting: ceiling at least 4 inches from the wall, or wall 4 to 12 inches from the ceiling — never in the dead-air corner where smoke does not circulate. Avoid placement within 10 feet of a cooking appliance (false alarms) or within 3 feet of a bathroom door (steam triggers). We walk the house with the NFPA 72 checklist in hand.
What We Do NOT Do
Hardwired interconnected detector systems on a new 120V circuit are licensed electrician work — that includes wiring a new detector loop, replacing a hardwired unit when the wire-nut connection has a problem, or interconnecting battery units with a hardwired backup. If your home has hardwired detectors and the issue is the wiring itself, we will route you to a licensed Washington L&I electrician. We do replace hardwired units one-for-one (same circuit, same wire-nut connection) when the install is straightforward, but we do not modify the wiring.
How Detector Replacement Works
Six sequential steps from the manufacture-date audit to the test-button verification — the actual sequence we follow on every smoke and CO detector swap visit.
Whole-Home Detector Audit
Walk the house, pull every existing unit off its mounting base, read the manufacture date stamped on the back of each one, and write it down. The 10-year expiration runs from the manufacture date, not the install date — a unit installed yesterday but manufactured in 2014 is already past due. About thirty minutes for a typical home.
NFPA 72 Placement Assessment
Walk the house against the NFPA 72 minimum — one smoke alarm on every level including the basement, one inside every bedroom, one outside every sleeping area, CO alarms within ten feet of every sleeping-area door. We flag missing locations (commonly basement, or CO outside a basement bedroom) and wrong placements (within ten feet of a stove, within three feet of a bath door).
Old Units Removed, Bases Checked
Pull each expired unit from its mounting base, inspect the base for damage, and either reuse the existing base if it is in good shape or swap it for one matching the new unit's brand. Base swap is forty dollars per location when needed.
New Unit Selection (Battery, Sealed-Lithium, Combo)
Default to 10-year sealed-lithium for set-and-forget operation (no battery changes for a decade, hush button built in instead of pulling the battery). Combo smoke/CO units at sleeping-area locations to cover both NFPA 72 requirements in a single ceiling location. Battery-replaceable units where the homeowner specifically prefers them.
Mount on Ceiling or Wall Per Code
Ceiling at least four inches from the wall, or wall four to twelve inches from the ceiling — never in the dead-air corner where smoke does not circulate. Avoid placement within ten feet of cooking appliances (false alarms) or within three feet of a bathroom door (steam triggers). About fifteen minutes per detector.
Test-Button Verification & Written Record
Press the test button on every newly installed unit, confirm the alarm sounds and the CO sensor (where applicable) cycles, and hand off a written record of every detector age in the home — what was replaced, what was kept, what NFPA 72 placements were added. The homeowner knows the date for the next ten-year cycle.
Detector Replacement Pricing
Final pricing depends on unit count, unit type (battery vs sealed-lithium, smoke-only vs combo), and whether mounting bases need to be swapped. Hardwired systems route to a licensed electrician. Request a free estimate for an accurate quote.
How many detectors, what age — battery or 10-year sealed? We will audit and quote the visit.
Why Homeowners Book Handis for Detector Work
Detector replacement is the work that happens once a decade per unit, which is exactly long enough to forget. A house full of 10-year-old battery detectors is operating on borrowed time — the smoke sensor itself degrades, the chamber gets dust, the response time stretches. NFPA 72 sets the 10-year limit not as a manufacturer suggestion but as a code-driven hard ceiling based on sensor chemistry. After a few hundred audits across Seattle homes — older houses with detectors from the early 2010s, builder-grade installs from the 2000s where the wrong types are mounted in the wrong rooms, brand-new construction with hardwired units where someone has already pulled the battery from the backup — the pattern is the same. At least one detector is past due, at least one location is missing, and at least one combo unit was installed without anyone noticing the CO sensor has expired ahead of the smoke side.
Manufacture date read on every unit
The 10-year expiration is from the manufacture date, not the install date. A detector that was installed yesterday but manufactured in 2014 is already past due. We pull every unit, read the date on the back, and write it down. By the end of the visit you have a record of every detector age in your home and a clear picture of what was kept and what was replaced.
NFPA 72 placement, not just wherever it was
Most homes have at least one detector in the wrong location or one location with no detector. The most common gaps we find: no detector inside the bedroom (only in the hallway outside), no CO alarm outside the basement bedroom, no smoke alarm in the basement at all, a kitchen-adjacent detector inside the 10-foot false-alarm radius. We walk the house against the NFPA 72 minimum list and tell you what to fix. The placement audit is included in every whole-home visit.
Sealed-lithium 10-year as the default
The trade-off used to be — battery units (cheaper, replaceable batteries, false-alarm hush requires pulling the battery) vs hardwired (interconnected, no battery worry, electrician install). Sealed-lithium 10-year units split the difference: no battery to change, a button to hush a false alarm without disabling the unit, and a 10-year service life that matches the sensor chemistry. We default to sealed-lithium for new installs and recommend the upgrade on every swap unless you specifically prefer battery-replaceable.
Combo units when CO is required
NFPA 72 requires CO detection within 10 feet of every sleeping-area door. The two ways to comply are a separate CO detector at each location, or a combination smoke/CO unit that covers both. We default to combo units at sleeping-area locations because the wall or ceiling holds one unit instead of two and the install time is the same. The CO sensor inside a combo unit expires at 5 to 7 years (per the manufacturer); the whole combo unit typically gets replaced when the CO side reaches end of life rather than waiting for the smoke side.
Honest boundary — we do not touch hardwired wiring
If your home has hardwired interconnected detectors and the issue is the wiring (a unit that does not get power, a circuit that has been disconnected, a backup battery that does not hold), the wiring fix is electrician work. We will replace a hardwired unit one-for-one on the same circuit and same wire-nut connection when the connection is straightforward, but we will not pull new wire, add a new circuit, or modify the existing detector loop. We will tell you on the booking call and route you to a licensed Washington L&I electrician for the wiring portion.
Estimate
Tell us how many bedrooms the home has, how many levels (including basement), whether you have a gas furnace or attached garage (CO consideration), and whether the existing detectors are battery or hardwired. We will quote the audit and swap.
Customer Reviews
Smoke and CO detector replacement reviews from real Handis customers.
Whole-home swap. Six units, all of them past the 10-year mark. The tech read the manufacture date on each one before he started — confirmed five were expired and one was the wrong type for the location (smoke-only outside a bedroom, no CO at all). Replaced all six with 10-year sealed-lithium combos, mounted per NFPA 72. No more chirping in the middle of the night, and now we actually have CO detection.
New construction, builder had installed hardwired interconnected units throughout but the backup batteries had all died by year three. Tech swapped the backup batteries on the units he could (most), pointed out two units that had a wiring issue he could not fix, and gave me the name of an electrician for those two. Appreciated the upfront honesty — most handymen would have just punted the whole job.
Audit-only visit. Tech walked the house, pulled every detector, read every manufacture date, and gave me a written list of what to replace and what to add. He found that our basement had no detector at all (NFPA 72 requires one on every level) and that the master bedroom only had a hallway detector outside. I bought the units myself online with his model recommendations and he came back the next week to install. Saved me from buying the wrong things.
Sealed-lithium upgrade across the whole house. We were tired of false alarms in the middle of the night from old units in the kitchen-adjacent zone. The tech swapped all four detectors for 10-year sealed units, repositioned the kitchen-adjacent one 12 feet from the stove (it had been too close), and showed me how to use the hush button instead of pulling the battery. Three months in, zero false alarms.
Three-unit small condo swap. Two smoke detectors and one CO. Tech read the manufacture dates (one was 2013, one was 2016, the CO was 2019), confirmed all three needed replacement (the CO was within service life but it was a battery unit that had not been changed in years), and installed sealed-lithium combos at all three locations. About 50 minutes for the whole visit including the audit.
Frequently Asked Questions
Common questions about smoke and CO detector replacement — NFPA 72 placement, battery vs sealed-lithium, and what routes to an electrician.