Smoke, carbon monoxide and detecting the guest who smokes indoors

Fire is the risk in short-let accommodation with the most serious consequences and the clearest obligations, and smoking indoors is the most common cause of both damage and disputes. It is also an area where connected detection genuinely changes outcomes, because the property is frequently occupied by people who do not know the building and unoccupied for long stretches between guests.

Getting this right is partly a legal question and partly a practical one, and the legal part comes first.

Start with the obligations, not the technology

Letting property to the public brings fire safety duties that are far more demanding than those on a private home. The specifics vary considerably by country and increasingly by city, and in several places short-let accommodation has its own regime.

What is broadly consistent: a fire risk assessment is expected, detection must be provided to a specified standard, escape routes must be usable without keys, and guests must be given fire safety information. In many jurisdictions detection in let accommodation must be mains-powered and interlinked rather than standalone battery units, and there may be requirements for emergency lighting, fire blankets or extinguishers.

Why connected detection is still worth having

An interlinked alarm sounds in the property. That wakes and protects the guests, which is its job. It does nothing if the property is empty, and it tells you nothing at all.

Connected detection adds three things a compliant system does not. You learn about a fire in an empty property immediately rather than when a neighbour calls. You learn that an alarm sounded while guests were present, which lets you check on them and respond. And you get a record, which matters for insurance and for disputes.

The cheapest route, if replacing compliant alarms is not proportionate, is an alarm sound listener — a device that recognises the standard alarm pattern of existing detectors and relays it. It leaves the certified system untouched and adds the notification layer for very little.

Carbon monoxide, which is frequently overlooked

If the property has any fuel-burning appliance — gas boiler, gas hob, wood burner, open fire, gas fire — or an attached garage, it needs carbon monoxide detection. In many countries this is a legal requirement for let accommodation specifically.

CO is more dangerous in short lets than in homes for a simple reason: guests do not know the property. They may use a wood burner incorrectly, block a vent, or fail to recognise symptoms in an unfamiliar place. Sealed ten-year CO alarms in the right locations are inexpensive, and connected versions let you know before a guest becomes seriously unwell.

Place them in the same room as any fuel-burning appliance, at roughly head height and one to three metres away, plus one near sleeping areas — CO mixes with air rather than rising like smoke, so ceiling mounting is not required.

Detecting smoking and vaping

This is the commercial problem: a guest smokes indoors, the property smells for days, the next guest complains, and a deep clean or a deposit dispute follows.

What works

Air quality sensors measuring particulates and volatile organic compounds detect cigarette and cannabis smoke reliably, because both produce a sharp and distinctive rise in fine particulates. Purpose-built vape and smoke detection devices for hospitality exist and are increasingly common in hotels; they generally combine particulate sensing with algorithms tuned to distinguish smoking from cooking or aerosol sprays.

Vaping is harder than smoking. Vapour produces different particle characteristics, dissipates faster, and is more easily confused with steam from a shower or a kettle. Detection is possible but false positives and misses are both more common, and any supplier claiming near-perfect vape detection is overstating it.

What to do with a detection

The genuinely useful response is not confrontation but ventilation and scheduling. An alert during a stay lets you send a polite reminder of the no-smoking policy, which frequently resolves it. An alert also lets you allocate extra cleaning time before the next arrival rather than discovering the smell at turnover.

For a deposit claim, a particulate graph is supporting evidence rather than proof. It shows a rise consistent with smoking; it does not identify who or what. Combine it with the cleaner's report and photographs, and be prepared for the platform to weigh it as one input.

Disclosure, which is not optional

Any monitoring device in guest accommodation must be disclosed. This is both a legal matter in most jurisdictions and an explicit requirement of the major booking platforms, and the consequences of getting it wrong are severe.

Practically: list the devices in your listing before booking, not on arrival; state what each measures; and place them visibly. A smoke, CO or air quality sensor on a wall or ceiling in plain view, disclosed in the listing, is entirely acceptable to guests. The same device concealed is a serious problem — we cover why in occupancy, extra guests and hidden devices.

Noise as an early warning of the wrong kind of stay

Worth a brief mention here because it interacts with smoking detection. A sharp rise in particulates alongside a sharp rise in sound level, late at night, is a much stronger signal of a gathering than either alone — and a gathering is the scenario in which smoking indoors, damage and complaints all become considerably more likely.

Using two independent signals rather than one is the same corroboration principle that applies everywhere else in this field, and it substantially reduces the false positives that come from a guest cooking with a hot pan or taking a long shower. The rules governing what you may measure and how are covered properly in noise monitoring and the law, and they are stricter than most hosts assume.

Practicalities of an unoccupied property

Alerts must reach someone who can act. A notification to a phone in another country at three in the morning is not a fire response. Have a local contact — a neighbour, a cleaner, a co-host — and make sure a fire alert reaches them too.

Test after every long vacancy. Sensors go flat, hubs lose connections, and the routine test is the only way to find out before it matters.

Test the alarms physically on the schedule your regulations require, and keep the record. For let accommodation this is frequently a documented duty, not good practice.

Expect guests to interfere with detectors. A guest who wants to smoke may cover or remove a detector. Some hospitality-grade devices report tamper or removal, which is worth having — both for safety and because a removed alarm is itself the evidence.

A sensible configuration

1. Compliant interlinked smoke detection to your national standard, professionally advised.
2. CO detection wherever there is a fuel-burning appliance or attached garage.
3. A connected layer — either connected alarms or a listener device — so you learn about an activation immediately.
4. An air quality sensor measuring particulates, for smoking detection and cleaning scheduling.
5. All of it disclosed in the listing and visibly placed.
6. A local contact who also receives fire alerts, and a documented testing routine.

The order matters: the first two are about people and are legally required, the next two are about your business, and the last two are what make any of it work in practice.