What Are Massachusetts Landlord CO Detector Requirements?
A tenant moves into a three-decker in Somerville and notices the hallway CO alarm has no batteries. Under Nicole's Law, that is not a minor maintenance oversight, it is a landlord compliance failure with statutory consequences. Massachusetts landlord carbon monoxide detector requirements under M.G.L. chapter 148 section 26F 1/2 create a clear installation and maintenance framework for rental properties with fuel-burning appliances, attached garages, or other covered risk conditions. What many landlords and tenants do not realize is that Massachusetts also enforces anti-tampering rules under section 27A that can carry criminal penalties, including fines and imprisonment. Below: who must install CO alarms in Massachusetts rentals, what tenants must avoid doing to those devices, where alarms must be placed, and how fire-department inspection workflows affect compliance.
Last verified: August 24, 2026
Key Takeaways
- Massachusetts requires CO alarms in rental units with fuel-burning appliances, attached garages, or other covered risk conditions under M.G.L. c.148 section 26F 1/2.
- Landlords must install and maintain required alarms at the start of each tenancy and throughout occupancy.
- Tenants may not tamper with, disable, or remove CO alarms; violations of section 27A can carry fines and imprisonment.
- Placement runs on maximums under 527 CMR 1.00 section 13.7.6, one alarm per level including finished basements, and none more than ten feet from a bedroom door.
- At sale or transfer, local fire departments conduct inspections to verify CO alarm compliance before the transaction closes.
- Combination smoke/CO alarms are permitted when they meet Massachusetts listing and approval standards.
Legal Summary
Massachusetts rental units fall under the same statute that covers owner-occupied homes, M.G.L. chapter 148 section 26F 1/2, the law commonly known as Nicole's Law. The law requires approved carbon monoxide alarms in residential occupancies where fuel-burning appliances, enclosed parking risk conditions, or other covered triggers are present. For rental properties, this means most apartments, duplexes, and leased single-family homes with gas furnaces, water heaters, boilers, or attached garages fall within the statutory scope.
The Massachusetts framework is notable for two features that set it apart from most other states. First, section 26F 1/2 creates a pre-transfer inspection workflow: when a property is sold or transferred, the local fire department conducts an inspection to verify that required CO alarms are installed and operational. Second, section 27A provides explicit anti-tampering language that prohibits disabling, removing, or obstructing required detection devices, and backs that prohibition with criminal penalties including fines and imprisonment.
For rental operators, compliance means more than having devices on the wall. It means maintaining approved alarms that are operational at tenancy start, preserving compliance documentation for fire-department review, and ensuring that neither landlord nor tenant interferes with required devices during occupancy.
Who Rental Rules Cover
Massachusetts CO alarm rules under section 26F 1/2 cover residential occupancies where statutory trigger conditions exist. In rental contexts, that includes leased single-family homes, apartments, duplexes, condominiums, and multi-unit buildings with fuel-burning appliances or attached garages. The statute does not limit its scope to large portfolio operators, a single-unit landlord renting one property with a gas water heater is equally covered.
The law's reach also extends beyond standard residential leases. Hotels and lodging houses fall within covered occupancy categories, which means short-term rental operators and hospitality properties may face the same alarm requirements. The trigger is risk-based: the presence of combustion equipment or an attached garage determines coverage, not the building label or lease duration. Landlords should evaluate each unit's actual equipment and building conditions rather than relying on assumptions about exemptions based on property type.
Landlord Responsibilities
Massachusetts landlords carry the primary compliance duty for CO alarms in rental properties. Under M.G.L. chapter 148 section 26F 1/2, the landlord must provide and maintain required carbon monoxide alarms in every covered rental unit. That obligation begins at the start of the tenancy, the unit must have operational, approved alarms before the tenant takes possession.
The landlord's duty is not limited to initial installation. Ongoing maintenance means ensuring devices remain operational throughout occupancy, replacing batteries or expired units, and addressing any deficiency reported by the tenant. When a tenant reports that a CO alarm is beeping, missing, or not functioning, the landlord must treat that report as a compliance repair item, not a convenience request.
Massachusetts also imposes a compliance verification step during property transactions. At sale or transfer, the local fire department inspects the property to confirm that required CO alarms are in place and operational. While this inspection is formally part of the transfer workflow, it creates a practical maintenance incentive for rental operators: landlords who maintain devices proactively avoid last-minute inspection failures and transaction delays.
Landlords should keep dated records of alarm installation, battery replacement, device age, and fire-department inspection results. These records strengthen defensibility during inspections, tenant disputes, and the eventual sale or transfer of the property. Documentation tied to specific statute sections is more defensible than generic maintenance logs.
Tenant Responsibilities
Massachusetts assigns tenants a clear prohibition rather than an active maintenance duty. Under M.G.L. chapter 148 section 27A, tenants may not tamper with, disable, or remove required carbon monoxide alarms. This is not a soft suggestion, section 27A backs the prohibition with penalties that can include fines and imprisonment. A tenant who removes batteries, disconnects a hardwired alarm, or obstructs a required device is exposed to criminal enforcement rather than to a lease violation alone.
Beyond the anti-tampering rule, tenants should report CO alarm deficiencies to the landlord promptly when they become aware of a problem. While the primary installation and maintenance duty belongs to the landlord, tenant reporting creates a documented chain that triggers the landlord's correction obligation. Written reports through email or maintenance portals create the strongest record for both parties.
The practical takeaway for Massachusetts tenants is straightforward: do not interfere with CO alarms, report problems in writing, and understand that section 27A treats tampering as a serious legal matter with potential criminal consequences.
Installation, Placement, and Device Rules
Massachusetts writes its placement rule in maximums rather than in adjectives, and the figures are worth having in front of you before an inspection. Under 527 CMR 1.00 section 13.7.6 an alarm goes on each level of a dwelling unit, finished basements and cellars included, with crawl spaces and uninhabitable attics the two exceptions. Section 13.7.6.5(3) sets the distance: no more than ten feet from each bedroom door, measured in any direction. The alarm goes outside the bedroom and does not displace the separate smoke alarm requirement inside it.
Two further rules sit in the building code rather than the fire code, which is why a landlord reading only one of them gets an incomplete answer. Where fuel-burning equipment is installed in a bedroom or its attached bathroom, 780 CMR 5313.4.3 puts an alarm in that room, and on any story with a bedroom the alarm sits outside the bedroom at a minimum. And 780 CMR 5313.4.4 requires alarms to sound at a minimum of 85 dBA at ten feet, with a combination smoke and carbon monoxide device carrying a voice announcement naming which hazard it has detected. That last requirement quietly rules out a large part of the combination market.
What qualifies is a specification rather than a brand, and for a building of 2008 or later it has three parts. The device has to be voice alert. Its smoke half has to be photoelectric, because 780 CMR 5313.4 describes the covered device as a combination photoelectric smoke and carbon monoxide alarm. And it has to be hardwired and interconnected, so that one alarm sounding sets off the rest. Those three sit together in the residential compliance guidance Weymouth's fire department publishes for the inspections it carries out, which is guidance reproducing the code rather than the code itself.
An older building runs on the other track and gets more room on one point only. A residence built or renovated before 2008 sits under M.G.L. chapter 148 section 26F1/2 and 527 CMR 31, where the alarm may be battery, plug-in with battery backup, hardwired, or a combination device. The voice-alert rule follows a combination unit onto that track as well. What the older track relaxes is the power source, not the announcement.
The shelf narrows twice more. Any alarm in a dwelling unit or common space within 20 feet of a kitchen, or of a bathroom with a shower or tub, has to be photoelectric only. And the two halves of a combination device wear out on different clocks: the smoke half at ten years under NFPA 72, the carbon monoxide half at five to seven unless the manufacturer specifies otherwise. A combination unit is retired on the shorter of the two, so the saving on buying one device instead of two is spent again sooner than an owner expects.
These placement rules apply to covered rental units with fuel-burning appliances, attached garages, or other statutory trigger conditions.
The device itself must be an approved and operational carbon monoxide alarm that conforms with Massachusetts statutory and fire-code requirements. Combination smoke and CO alarms are permitted when the device meets applicable listing standards and provides distinct alarm signals for each hazard type. Landlords should follow manufacturer installation instructions for mounting height, distance from appliances, and recommended locations to avoid nuisance alarms.
For multi-unit buildings, each covered unit and common area has to meet the placement requirements on its own. Building-wide compliance cannot be assumed from a single hallway device when individual units contain their own fuel-burning equipment.
Move-In, Testing, Maintenance, and Notice
The Massachusetts rental compliance workflow starts before move-in. The landlord must have the required CO alarms installed and operational when the tenant takes possession. A unit that is missing a required alarm or has an expired device at handoff is noncompliant from day one.
During tenancy, landlords should maintain a recurring testing and maintenance schedule. This includes battery replacement for battery-powered devices, end-of-life tracking for device replacement, and documented response to tenant deficiency reports. Massachusetts does not prescribe a specific testing interval in the statute, but regular testing aligned with manufacturer instructions and fire-code guidance is the defensible operational standard.
For entry, landlords should follow applicable Massachusetts landlord-tenant access rules when entering units for CO alarm service. Maintaining a documented service-access procedure protects compliance standing and supports the landlord's ability to restore operability during tenancy. Records of each device test, battery change, and replacement should be retained for fire-department inspection readiness, especially given the pre-transfer inspection workflow under section 26F 1/2.
Enforcement, Complaints, and Tenant Remedies
Massachusetts enforcement of CO alarm requirements is primarily handled by local fire departments. Under the section 26F 1/2 framework, fire departments conduct inspections at sale or transfer checkpoints to verify compliance. They also respond to enforcement actions when devices are found to be missing, disabled, or noncompliant during routine fire inspections or complaint-driven investigations.
A tenant who cannot get the alarm fixed should understand which office opens which door, because writing to the landlord opens neither. The fire department enforces the section 26F 1/2 installation duty and can inspect and order correction. The money remedies run through a different agency: repair and deduct under M.G.L. chapter 111 section 127L becomes available only after a board of health or code enforcement inspection certifies a violation and written notice reaches the owner, and the rent defence under M.G.L. chapter 239 section 8A turns on the owner having known of the condition, which a written board of health notice establishes by presumption from the date the owner received it. Calling the board of health is therefore the step that starts the clock, and a tenant's own letter supports the case without beginning it. Keep copies of every request and of any inspection report.
The enforcement pathway is local, inspection timing, documentation requirements, and follow-up procedures can vary by municipality. Landlords should confirm their local fire department's specific process rather than relying on a single statewide template.
What a Tenant Can Do in Massachusetts
When a carbon monoxide alarm stops working in a rented home in Massachusetts, these are the five routes a tenant can take and where each one comes from.
"Via general law" means the Massachusetts carbon monoxide statute itself is silent and the remedy comes from the state's landlord-tenant law instead. The remedy is available even though the alarm rule does not contain it.
"No provision found" is a finding rather than a gap in the research: the chapter that would carry that remedy was read and contains nothing either way. What was read is named beside the row.
| Rent withholding | Via general lawM.G.L. c.239 8A. Framed as a defence and counterclaim in a possession case: the tenant claims the difference between the agreed rent and the fair value of the use and occupation. The owner must have known of the conditions before the tenant fell into arrears, and a written board of health inspection notice creates a presumption that the owner knew from the date it was received. The court may require the tenant to pay the fair value into court, and there is no recovery of possession where the counterclaim equals or exceeds what the landlord is owed, or where the tenant pays the balance within one week of the court's notice. |
|---|---|
| Repair and deduct | Via general lawM.G.L. c.111 127L. Capped at four months' rent in any twelve-month period or period of occupancy, whichever is shorter, computed on the highest monthly rent in that window. The gate is a certified violation of the standards of fitness for human habitation plus written notice to the owner, so this is not a remedy a tenant can start alone. |
| Right to end the lease | No provision foundSearched: M.G.L. chapter 186 (landlord and tenant), chapter 239 section 8A, chapter 111 sections 127A to 127L, and the State Sanitary Code at 105 CMR 410. No provision lets a tenant end the tenancy over an uncorrected code violation. The route is constructive eviction, which is common law, requires the condition to be serious enough to force the tenant out, and requires the tenant to leave, so it ends the tenancy by abandonment rather than by a statutory right exercised on notice. |
| Notice the tenant must give | Via general lawM.G.L. c.111 127L; M.G.L. c.239 8A. No statutory waiting period attaches to anything the tenant sends, because the tenant's notice is not what starts the repair-and-deduct clocks. Those run from the code agency's written notice to the owner. A tenant's own written notice still matters for the 8A defence, where it goes to proving the owner knew, and an inspection notice does the same job by presumption. |
| Landlord cure period | Via general law, 14 daysM.G.L. c.111 127L. Two clocks inside one section, both running from the written notice: five days to begin the repairs or contract for them, fourteen days to substantially complete them. A shorter period can be ordered, which is the opening for a live CO hazard. The fourteen days is recorded here because it is the point at which the tenant's own remedy becomes available. |
Applies to every row above:Nicole's Law and the State Sanitary Code put the alarm duty on the owner and neither creates a tenant remedy, so all five columns come from general law. Massachusetts then differs from every other state in the fifty-one in one structural way: its strongest remedy is gated on an official certification rather than on the tenant's own letter. Missouri asks for a municipal certification too, but only where the landlord disputes the repair in writing. Here it is the default. The repair-and-deduct clocks in c.111 127L run from a board of health or code enforcement certification and written notice to the owner, which means the practical first step for a Massachusetts tenant is to call the board of health, not to write to the landlord. The trade for that extra step is the highest ceiling any capping state puts on a single repair, four months' rent, against California's one and Illinois's $500. Two things a reader should have beside that: five states cap nothing at all, and Hawaii allows more across a year, three months' rent every six months against the four months Massachusetts allows every twelve.
Penalties and Liability
Massachusetts provides meaningful penalty exposure for CO alarm violations. M.G.L. chapter 148 section 27A prohibits disabling or removing required detection devices and authorizes penalties that can include both fines and imprisonment. This is a criminal penalty framework, not merely a civil fine, making Massachusetts one of the stricter states for CO alarm enforcement.
Beyond statutory penalties, landlords face civil liability exposure when a required alarm is absent or inoperable during a CO incident. Failed fire-department inspections can delay property transfers and create documented compliance gaps. The combination of criminal penalty risk under section 27A and practical transaction consequences under the pre-transfer inspection workflow creates strong financial incentive for proactive compliance rather than reactive correction.
Local Override Warning
Chapter 148 sets the baseline and three Massachusetts cities have already gone past it, so a landlord needs the local answer as well as the statewide one. In Boston, Subsection 9-1.4 of the municipal code makes the owner provide and maintain working CO alarms on the day a unit is handed to a new tenant, and a tenant who asks within 24 hours gets an Inspectional Services inspection within two business days. Two limits sit beside that, one in the definitions and one in the subsection next door. NEW TENANT covers a letting of more than 30 days, so a short stay falls outside Subsection 9-1.4 altogether and takes the handover duty and the 24-hour route with it. And Subsection 9-1.3 puts a separate duty on the owner to request a full inspection within 45 days of turnover, which runs whether or not the tenant asks for anything. Boston also prices that inspection rather than leaving it to the fire department: Subsection 18-1.19(O) fixes the fee for a smoke and carbon monoxide inspection ordered under M.G.L. chapter 148 sections 26F and 26F1/2 at $50 for a single-family dwelling or a single unit, $100 for a two-family, $150 for a building of six units or fewer and $500 above that, with a reinspection charged at the same rates. Holyoke runs its own ordinance at Section 42-17, with a sale-or-transfer inspection and an alarm placed at least 15 feet from the heating unit. Gloucester puts the alarm in the short-term rental permit at Section 5-66(s). Cambridge, Somerville, New Bedford, Salem, Brockton, Chelsea, Lawrence, Medford, Peabody, Westfield, Newburyport and Winthrop were read on the same day and add nothing. Worcester, Springfield, Provincetown, Nantucket and Malden could not be read, so treat those five as open. Fire-department inspection practice and paperwork vary everywhere, and the full list of what was checked sits on the Massachusetts state page.
One thing about how to look is worth knowing before you look. M.G.L. chapter 143 section 98 routes a stricter local building standard through the state board, so a Massachusetts city cannot write its own construction rule for alarms. That is why an earlier version of this survey concluded a city's own code could not answer the question at all, and it was half right in a way that cost four months. Section 98 stops a city writing a building standard; it does not stop a city legislating about carbon monoxide by some other power. Boston used its housing-standards power, Gloucester attached a condition to a licence, and Holyoke wrote a fire-prevention ordinance. So read the city code, and read it for housing standards, licensing conditions and fire prevention rather than for a building rule that cannot be there.
Frequently Asked Questions
Does Nicole's Law require CO detectors in Massachusetts rental properties?
Who is responsible for CO detectors in Massachusetts rentals: landlord or tenant?
Where must CO alarms be installed in a Massachusetts rental unit?
What are the penalties for tampering with a CO alarm in Massachusetts?
Do Massachusetts landlords need a fire department inspection for CO detectors?
Can a Massachusetts tenant be fined or jailed for removing a CO detector?
Disclaimer: This page explains the law as it stood on August 24, 2026. It is general information, not legal advice, and reading it creates no attorney-client relationship. Requirements vary by city, county and building type, and statutes and codes are amended: confirm the current text with the issuing authority before acting on it. Each requirement here cites the instrument it comes from, so you can check it at source.
Sources and References
- Massachusetts General Laws chapter 148 section 26F 1/2 (Nicole's Law) , Primary statutory framework for CO alarm requirements, triggers, placement, transfer inspection
- Massachusetts General Laws chapter 148 section 27A (anti-tampering) , Anti-tampering prohibition and penalty provisions for required detection devices
- Massachusetts law about carbon monoxide detectors (mass.gov official guidance) , Statute and fire-code reference summary, implementation guidance