Carbon Monoxide Detector Requirements: State Laws, Placement, and Smart Home Integration

Carbon monoxide (CO) is called “the silent killer” for good reason — it’s colorless, odorless, and produces symptoms that are easily confused with the flu. The CDC estimates that approximately 400 Americans die from unintentional CO poisoning unrelated to fires each year, and more than 100,000 visit emergency rooms. Most of these deaths are preventable.

CO detector requirements vary significantly by state, but the trend is clear: requirements are expanding, combination smoke/CO detectors are becoming standard, and smart home integration is increasingly available. This guide covers where you’re legally required to have CO detectors, placement best practices, device types, and smart home integration options.

What Is Carbon Monoxide and Where Does It Come From?

Carbon monoxide is produced by the incomplete combustion of carbon-based fuels. Common household sources include:

  • Gas furnaces and boilers (most common cause of residential CO poisoning)
  • Gas water heaters
  • Gas ranges and ovens
  • Fireplaces and wood stoves (when flue is blocked or inadequately vented)
  • Attached garages (car exhaust, gas-powered tools)
  • Portable generators (the leading cause of CO death; should never be operated indoors or near open windows)
  • Gas dryers
  • Charcoal grills and propane heaters (when used indoors)

Modern homes are tighter and better insulated than older construction — which means CO from combustion appliances can accumulate more quickly when venting is blocked, damaged, or insufficient.

State-by-State CO Detector Requirements

Requirements vary significantly. Below is a summary of major states as of 2026. For your specific jurisdiction, always verify with local building or fire departments.

States with Comprehensive CO Detector Laws

California: CO detectors required on each floor of a dwelling unit, outside each sleeping area. Required in all existing residences. Seller disclosure required. Combination smoke/CO units acceptable.

New York: All residences must have CO detectors within 15 feet of sleeping areas. Combination smoke/CO alarms required in new construction (2015+). Applies to all rental units regardless of when built.

New Jersey: CO detectors required on each floor, outside each sleeping area. Required when a home is sold or a rental unit changes tenants.

Illinois: Requires CO detectors in residences with attached garages, fuel-burning appliances, or fireplaces. Must be within 15 feet of each sleeping area.

Washington: CO alarms required adjacent to each sleeping room. Required in new construction and when remodeling or selling.

Colorado: CO detectors required in any residence with fuel-burning appliances or attached garages. Required on each floor.

Massachusetts: CO detectors required when selling a home; placement near sleeping areas and fuel-burning appliances.

Florida: Required in new construction in all dwelling units with attached garages or fuel-burning appliances. Existing homes required to comply when sold.

Texas: No statewide requirement as of 2026, but many municipalities have adopted local ordinances. Check local codes.

Ohio: No statewide mandate, but strongly recommended by state fire marshal. Local requirements vary.

Federal Buildings and Rental Properties

Federal law requires CO detectors in federally assisted housing (HUD properties). Many states require landlords to provide CO detectors in rental units — tenant rights laws vary significantly.

When Requirements Apply

Most state laws apply at the time of:

  • New construction (always required)
  • Major renovation or addition
  • Point of sale (common trigger)
  • Change in tenancy (rental units)

Existing homeowners not triggering these conditions may technically not be required to install detectors under some state codes — but CO poisoning doesn’t care about legal technicalities. Installation is strongly recommended regardless of legal requirement.

CO Detector Placement: Where to Put Them

Unlike smoke detectors (which go on the ceiling), CO placement requires some nuance because CO is roughly the same weight as air and disperses relatively evenly throughout a space.

Primary Placement Locations

Outside each sleeping area: This is the minimum requirement in most codes. CO poisoning often occurs at night because occupants are asleep and don’t notice symptoms until CO levels become dangerous.

On every floor: CO can accumulate on any level. A basement furnace issue can produce CO that reaches upstairs sleeping areas before alarming.

Near attached garages: Running a car in an attached garage for even 30 seconds can push CO into the living space. A detector near the garage-home connection point provides the fastest warning.

Near fuel-burning appliances: Consider a detector within line-of-sight of gas furnaces, boilers, or water heaters — not directly above, but nearby. This can provide early warning of a combustion problem before CO reaches bedrooms.

Where Not to Place CO Detectors

  • Within 5 feet of fuel-burning appliances: False alarms from startup; place nearby but not immediately adjacent
  • In garages: Normal car exhaust would cause constant nuisance alarms
  • In very high or very low humidity areas: Extreme conditions can affect sensors
  • Directly in line with cooking appliances: Normal cooking can trigger alarms

Height Placement

Most manufacturers recommend mounting CO detectors on the wall 5 feet from the floor, or on the ceiling. Since CO disperses throughout the room (unlike smoke, which rises), ceiling and wall placement are both effective. Follow the specific manufacturer recommendation.

If using a combination smoke/CO unit mounted on the ceiling, the CO sensing may be slightly less optimal but is generally considered acceptable.

CO Detector Types

Electrochemical Sensors (Most Common)

The vast majority of residential CO detectors use electrochemical sensors. A chemical reaction proportional to CO concentration produces an electrical current that triggers the alarm. These sensors are accurate and have low power consumption.

Lifespan: 5–7 years
Cost: $20–$60 for standalone units

Metal Oxide Semiconductor (MOS) Sensors

Less common in residential applications. MOS sensors use a tin oxide element that changes resistance in the presence of CO. They’re less accurate and more prone to false alarms from humidity and other gases, but are inexpensive.

Biomimetic Sensors

Biomimetic sensors use a gel that changes color in the presence of CO, triggering an alarm. They’re durable and have long lifespans, but are slow to respond at low concentrations. More common in marine/RV applications than residential.

CO Detector Lifespan and Replacement

CO detectors have a sensor lifespan of 5–7 years. Unlike smoke detectors, CO detectors don’t simply “stop working” when the sensor degrades — they may continue to alarm or not alarm in ways that don’t reflect actual CO levels.

Replace every 5–7 years. The manufacture date is on the back of the device. Many units display a “replace” indicator when the sensor reaches end of life.

Monthly testing with the TEST button confirms the alarm circuit is functional, but doesn’t verify sensor accuracy. Only replacement at the end of sensor life ensures ongoing protection.

Smart Home CO Detectors

Smart CO detectors add connectivity, mobile notifications, and integration with home automation systems.

Nest Protect

The Nest Protect (2nd generation) is the most popular smart combination smoke/CO detector. Features include:

  • Mobile alerts via Google Home app when CO is detected
  • “Heads Up” alerts at lower CO levels before full alarm
  • Self-testing (tests automatically, no manual button press needed)
  • Integration with Google Home, Alexa, and IFTTT
  • Speaks the type and location of hazard: “There is carbon monoxide in the hallway”
  • 10-year sealed battery or hardwired

Cost: $119 per unit
Best for: Smart home users who want mobile alerts and integration

First Alert and Kidde both offer connected combination units with app-based notifications and voice alerts. Integration with Amazon Alexa is available for voice announcements.

Cost: $50–$80 per unit

Smart Home Integration Benefits

  • Remote notification: Get alerted on your phone even when away from home (useful if house is empty — you can dispatch a neighbor or emergency services)
  • Location awareness: Multi-detector systems identify which detector triggered
  • HVAC integration: Some systems can auto-shut off HVAC when CO is detected to stop circulating the gas
  • Battery monitoring: Get alerts before batteries die
  • History logging: Review CO level history over time

Consideration: Z-Wave and Zigbee Detectors

For home automation enthusiasts using platforms like SmartThings, Home Assistant, or Hubitat, Z-Wave CO detectors (like the Fibaro CO Sensor) integrate directly into automation scenes and can trigger HVAC shutoff, send alerts, or unlock doors automatically.

What to Do If Your CO Detector Alarms

Low-level alert (chirping or intermittent): CO may be at a sub-dangerous but elevated level. Get fresh air, ventilate the home, and investigate the source before re-entering.

Full alarm: Evacuate everyone immediately. Do not stop to open windows or investigate. Call 911 from outside. Do not re-enter until emergency responders have cleared the home.

If someone has symptoms (headache, dizziness, nausea, confusion): Get to fresh air immediately and call emergency services. CO poisoning is a medical emergency.

CO Detector Installation and Inspection

A licensed electrician can install hardwired CO detectors or connected systems and ensure they’re placed correctly for code compliance.

When having HVAC work done, ask the technician to inspect combustion venting for blockages, cracks, or improper connections — faulty venting is the most common source of residential CO problems.

An annual furnace/boiler service visit should include inspection of heat exchanger integrity — a cracked heat exchanger is a primary source of CO infiltration and is not visible without professional inspection.

ProCraft connects homeowners with licensed HVAC technicians, electricians, and home safety inspectors for CO system assessments and appliance inspections.

Frequently Asked Questions

How many CO detectors does my home need? Minimum: one outside each sleeping area and one on each floor. For more complete protection, add one near fuel-burning appliances and near the garage-home connection.

Do all-electric homes need CO detectors? All-electric homes (no gas appliances, no attached garage) have very low CO risk. However, attached garages can still produce CO from vehicles, and electrical code in many states still requires CO detectors regardless of appliance type.

Can I use a combination smoke/CO detector for both purposes? Yes. Combination units are code-compliant for both smoke and CO requirements in virtually all jurisdictions. They’re increasingly the recommended choice for simplicity and consistent replacement.

How long does it take for CO to reach dangerous levels? At very high concentrations (1,200+ ppm), dangerous symptoms can appear in minutes. At the EPA action level for immediate danger (70 ppm), symptoms develop over hours. At lower chronic exposure levels (35 ppm), long-term health effects occur over years. Detectors are calibrated to alarm before dangerous concentrations are reached.

My CO detector keeps going off but I don’t smell anything. Is it malfunctioning? You can’t smell CO — the lack of odor doesn’t mean it’s absent. If your detector is alarming, treat it as real. Evacuate and call 911. If the responders confirm no CO, the detector may be reaching end of life (check the manufacture date), or there may be an intermittent CO source like a vehicle warm-up in the garage.

Should I get a CO detector if I have a gas furnace? Yes, absolutely. Gas furnaces are the most common cause of residential CO events. A cracked heat exchanger or improper venting can produce dangerous CO levels. Annual service and a CO detector are both essential.

What’s the difference between ppm and the alarm thresholds? CO is measured in parts per million (ppm). UL 2034 certification (required for U.S. detectors) requires alarms to sound: within 4 hours at 70 ppm, within 10 minutes at 150 ppm, and within 3 minutes at 400 ppm. The 400 ppm threshold represents immediately dangerous levels.