Guide · Gas Safety
Carbon monoxide incidents: what a landlord does, in order
Carbon monoxide is the rental sector's least forgiving emergency: colourless, odourless, and produced by exactly the appliances a landlord is responsible for maintaining. When an alarm sounds or symptoms appear, the response sequence matters more than any document in the compliance file — and what happens in the days afterwards decides whether the incident ever repeats. Here is the sequence.
Gas Safety
What happens in the first minutes of a suspected CO incident?
Evacuation first, investigation later: everyone out into fresh air, doors left open on the way, and no re-entry to silence the alarm, open more windows or hunt for the source. CO impairs judgement before it announces itself, which is precisely why the alarm — not how anyone feels — is the trigger that gets obeyed.
From outside, the call is to the national gas emergency line, which is free, staffed around the clock, and dispatches an engineer to make the situation safe. Anyone with symptoms — headache, dizziness, nausea, confusion — needs medical attention and should say CO exposure is suspected, because the presentation mimics ordinary illness and the test is specific.
Gas Safety
What is the tenant's role and what is the landlord's?
Tenants act on the emergency: evacuate, call the emergency line, seek treatment. The landlord's role begins the moment they are told — and the tenancy paperwork should have made telling easy, with the emergency number and the landlord's contact displayed in the property pack rather than buried in a clause nobody rereads under stress.
From notification, the landlord owns the follow-through: cooperating with the emergency engineer's findings, keeping the appliance out of use for as long as instructed, and commissioning the repair. What a landlord never does is authorise reconnection because the alarm has gone quiet — silence means dispersal, not resolution, and the fault that produced the gas is still there.
Gas Safety
What does the emergency engineer actually do?
The emergency response makes the property safe rather than fixed: isolating the gas supply or the suspect appliance, checking for escapes, and tagging equipment that must not be used. It is a triage service, and its endpoint is a property that cannot poison anyone tonight — not a property whose boiler works again.
The permanent fix is the landlord's commission: a Gas Safe registered engineer investigating the appliance, flue and ventilation, diagnosing the cause — blocked flue, failed seal, poor combustion, obstructed air supply — and repairing or condemning accordingly. The distinction matters because incidents stall exactly here, in the gap between made-safe and made-right.
Gas Safety
Which faults produce carbon monoxide in rented homes?
Incomplete combustion is the common thread: flues blocked by nests or debris, terminals obstructed by later building work, ventilation openings sealed by well-meaning draught-proofing, appliances burning badly through age or maladjustment, and open-flued appliances starved of air in rooms modernised around them. Most of these are invisible from the living space, which is the argument for the annual check.
The pattern worth internalising is that CO faults are usually system faults, not appliance faults alone: the boiler, its flue, its air supply and the room it lives in function as one combustion system, and a change to any element — an extension, a new extractor fan, a blocked airbrick — can unbalance the rest.
Gas Safety
How does the incident connect to the gas safety record?
The annual gas safety check exists to catch these faults before they produce an incident: flue flow, spillage, combustion performance and ventilation are all within its scope. An incident between checks is therefore also a question — did anything change since the last record, and did the check's scope cover the appliance involved?
After the repair, the prudent close-out is a fresh safety check on the affected appliance with the paperwork filed alongside the incident notes. If the last record is approaching renewal anyway, bringing the whole check forward converts the incident into a clean, current baseline for every appliance in the property.
Gas Safety
What does the CO alarm estate need afterwards?
The alarm that worked has just proven its value and its exposure: units that have alarmed in earnest should be checked against the manufacturer's guidance, because some sensors are one-event or degrade after significant exposure. Testing every alarm in the property — and confirming one is present in each room with a combustion appliance — belongs in the same visit as the repair.
Replacement dates deserve reading rather than guessing: CO sensors have finite lives printed on the unit, and an estate installed together ages out together. The incident is the natural prompt to log every expiry date into the compliance calendar so replacement happens on schedule instead of on failure.
Gas Safety
What does the evidence trail look like when it's done well?
A dated file: the tenant's report, the emergency visit and its outcome, the investigating engineer's findings, the repair invoice, the post-repair safety check, the alarm tests and any replacements. Each item is mundane; together they demonstrate a landlord who responded promptly and competently — the exact question any later scrutiny will ask.
The file also feeds prevention: if the cause was a blocked flue, gutter-line vegetation or bird activity becomes an inspection item; if ventilation, alterations need a combustion check before sign-off. An incident that changes the maintenance routine has been converted from a near-miss into a system improvement — which is the only good ending available.
Need the certificate itself?
The Gas Safety Certificate (CP12) page covers cost, process and every UK area we serve.
FAQ
Related questions, answered
What if my tenant refuses access for the gas check?
You must take all reasonable steps: written requests, offering alternative dates, and keeping evidence of each attempt. You may not force entry. A documented paper trail of reasonable attempts is what the HSE expects if access is ultimately refused.
What is a CP12 gas safety certificate?
CP12 is the industry nickname for the Landlord Gas Safety Record — the document a Gas Safe registered engineer issues after checking each gas appliance, flue and pipework in a rental property. Landlords letting property in your area must have this check done every 12 months.
Do the same gas rules apply in Scotland, Wales and Northern Ireland?
Yes — the Gas Safety (Installation and Use) Regulations 1998 apply UK-wide (Northern Ireland has parallel regulations to the same effect). The annual check, the 28-day tenant copy rule and Gas Safe registration requirements are consistent across all four nations.
How long does a gas safety check take?
Typically around 30 to 60 minutes for a property with a boiler and one or two additional gas appliances. More appliances, or access issues, extend the visit.
Is a gas safety check the same as a boiler service?
No. The safety check confirms appliances are safe to use; a service is a maintenance clean and inspection of the boiler itself. Many landlords in your area book both together because the engineer is already on site, but only the safety check is a legal requirement.
Do tenants' own gas appliances need to be on my record?
Appliances owned by the tenant are not the landlord's responsibility to check, but the pipework serving them is, and any flue serving a tenant appliance that you own must be included. Note the division of responsibility in your tenancy agreement.
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Ready to act on this? The pillar page covers the certificate end to end, with every UK area linked: Gas Safety Certificate (CP12) · Smoke & CO Alarm Check.