Where are California landlords required to install smoke alarms?

Under Health & Safety Code §13113.7, every dwelling unit intended for human occupancy must have a working smoke alarm in every sleeping room, in hallways adjacent to sleeping areas, and on every story including basements. Alarms in single-family homes and units with multiple stories must be hardwired with battery backup if installed during major renovations or new construction; older units typically use 10-year sealed-battery alarms.

Are carbon monoxide detectors required in California rentals?

Yes under H&S §17926 in any dwelling with a fuel-burning appliance, attached garage, or fireplace. CO alarms have to be in proximity to every sleeping area. The requirement applies to single-family, multifamily, condos, and rentals. Failure to install is a misdemeanor as well as a habitability violation.

Who replaces batteries during a tenancy?

The tenant is responsible for routine battery replacement during the tenancy under H&S §13113.7. The landlord is responsible for ensuring the alarms are operational at move-in and for replacing alarms that fail or reach end of life. Most professionally drafted leases include a battery-replacement clause confirming the tenant's role.

Can missing smoke alarms invalidate an eviction?

Indirectly, yes. Missing or non-functional smoke alarms can support a habitability defense in unlawful detainer if the deficiency was substantial and the landlord had notice. The implied warranty of habitability covers smoke alarm compliance. A 3-Day pay-or-quit served on a tenant whose unit lacks working alarms walks into a habitability counterclaim.

Smoke & Carbon Monoxide Detectors in California Rentals 2026

TL;DR — 30 seconds

Smoke alarms in every sleeping room, every hallway adjacent to sleeping areas, every story (§13113.7). CO alarms in any unit with a fuel-burning appliance, attached garage, or fireplace (§17926). Landlord installs and ensures working at move-in. Tenant replaces batteries during tenancy. Missing alarms support a habitability defense.

Step 1 — Install where required

Smoke alarms (§13113.7):

Inside every sleeping room.
In every hallway adjacent to sleeping areas.
On every story of the unit, including basements.

CO alarms (§17926):

In proximity to every sleeping area.
Required if the unit has any fuel-burning appliance (gas range, gas water heater, gas furnace, fireplace) or an attached garage.

Use State Fire Marshal-approved units. Modern best practice is 10-year sealed-battery alarms (eliminates the battery-replacement issue) or hardwired with battery backup on major renovations.

Step 2 — Verify operational at move-in

Test every alarm at move-in. Document in the move-in inspection. Get the tenant to sign acknowledging the alarms are operational. This document is decisive if the tenant later claims the alarms didn't work at the start of the tenancy.

Step 3 — Set the battery-replacement responsibility in the lease

§13113.7 puts battery replacement on the tenant during tenancy. The lease should confirm this in writing. The landlord remains responsible for the operability of the alarm hardware — if the unit itself fails (not just the battery), the landlord replaces it.

Step 4 — Annual inspection

Annual property walks (with proper §1954 notice) include a smoke and CO alarm check. Test each one. Replace any unit that's failed. Document the check in the unit file. Annual inspections are also the standard moment to look for moisture, mold signs, and other habitability items.

Step 5 — Respond fast on tenant reports

A tenant report of a non-working alarm is an urgent habitability item. Respond same day or next day. Replace the alarm (not just the battery) if needed. Document the response. Slow response on alarms shows up badly in any later habitability claim and badly in any UD where the tenant raises habitability as a defense.

No alarms = no eviction

Serving a 3-day pay-or-quit on a unit with missing or non-functional alarms walks into the habitability defense. Fix the alarms first. Then pursue the rent. The same logic applies to every habitability item.

What goes wrong

Tenant disabled the alarm because it false-alarms during cooking. Landlord finds out at annual inspection. The fix is replacing the alarm with a model less prone to false alarms (photoelectric vs ionization) and documenting the conversation.
Alarm reaches end of life (typically 10 years). Date-of-manufacture is on the unit; alarms past their dated end-of-life have to be replaced regardless of battery status.
Multi-family building with shared egress paths: common-area alarms become a building-wide compliance issue, not just per-unit.

Common questions

Where do smoke alarms have to be installed?

Every sleeping room, every hallway adjacent to sleeping areas, every story. State Fire Marshal-approved units. §13113.7.

Are CO alarms required?

Yes under §17926 in any unit with a fuel-burning appliance, attached garage, or fireplace. In proximity to every sleeping area.

Who replaces batteries?

Tenant during the tenancy. Landlord ensures alarms work at move-in and replaces failed hardware.

Can missing alarms kill an eviction?

Indirectly. Missing alarms support a habitability defense in any UD. Fix the alarms before pursuing termination.

Smoke and CO Detectors — The California Landlord Checklist