New regulations requiring all landlords in the United Kingdom to install both Carbon Monoxide Detectors and Smoke Alarms came into effect on October 1st, 2015.

Smoke alarms are now required on every floor of a rented dwelling.

Carbon Monoxide alarms are required in any room which has a solid fuel burning appliance - strangely the legislation seems to overlook gas burning appliances.

Specifically section 7.6 of the legislation states::
These Regulations place duties on a “relevant landlord” of a “specified tenancy” of residential premises in England to ensure:

1. a smoke alarm is equipped on each story of the premises which is wholly or partly used as living accommodation;
2. a carbon monoxide alarm is equipped in any room which is used wholly or partly as living accommodation and contains a solid fuel burning combustion appliance; and
3. the smoke and carbon monoxide alarms are in proper working order at the start of any new tenancy.

So you don't need to install them right away, but they do have to be installed and properly working when you start your next tenant.

Stephen Williams, the Communities Minister, justified the new regulations by saying, "We’re determined to create a bigger, better and safer private rented sector – a key part of that is to ensure the safety of tenants with fire prevention and carbon monoxide warning".

Although the law does not require owner-occupiers to install carbon monoxide detectors, it's still the best thing to do - after all an owner's health and safety is no less important than that of a tenant.

For further information see: Explanatory Memorandum to the Smoke and Carbon Monoxide Alarm (England) Regulations 2015 .