Why Carbon Monoxide Alarms Matter in UK Rental Properties

Carbon monoxide (CO) is a colourless, odourless gas that can be fatal.

Under the Smoke and Carbon Monoxide Alarm (England) Regulations 2015, landlords must install carbon monoxide alarms in rooms containing fixed combustion appliances.

Since 2022 updates, this includes:

• Boilers
• Gas fires
• Oil-fired appliances
• Solid fuel appliances

Failure to comply can result in fines of up to £5,000 per breach.

If you’re a landlord, see our complete Landlord Safety Certificates UK Guide to understand your full legal responsibilities.

Electrical safety is equally important — read our full guide to EICR requirements for landlords.

You may also want to read our guide to the best smoke alarms for UK homes, especially if you’re upgrading your fire safety setup.

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Quick Comparison Table (Top Picks 2026)

Model	Power Type	Display	Sealed Battery	Best For
Kidde 10LLCO	Sealed Lithium	Yes	10 years	Best Overall
FireAngel CO-9X	Replaceable AA	Yes	No	Budget Choice
Aico Ei208	Sealed Lithium	No	10 years	Landlords
Google Nest Protect	Wired/Battery	Yes	Yes	Smart Homes
X-Sense CO03D	Replaceable	Yes	No	Value

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1. Best Overall: Kidde 10LLCO

Why It’s Our Top Pick

The Kidde 10LLCO combines:

• 10-year sealed lithium battery
• Digital display
• End-of-life warning
• Test/reset button
• Kitemarked to EN50291

This is the ideal balance between reliability and simplicity.

Pros

• 10-year lifespan
• No battery replacements
• Clear digital display

Cons

• Slightly more expensive than budget models

Best for: Most landlords and homeowners.

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2. Best Budget Option: FireAngel CO-9X

The FireAngel CO-9X is widely available in UK retailers.

Features:

• Replaceable AA batteries
• 7-year sensor life
• Loud 85dB alarm
• EN50291 certified

Pros

• Affordable
• Easy to install
• Digital screen

Cons

• Batteries need replacing
• Shorter lifespan than 10-year units

Best for: Lower-budget properties.

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3. Best for Landlords: Aico Ei208

The Aico Ei208 is trusted by many letting agents.

Manufactured by
Aico

Features:

• 10-year sealed battery
• Tamper-proof design
• Audio/visual alerts
• Compact

Pros

• Professional-grade
• 10-year warranty
• Reliable brand

Cons

• No digital display

Best for: Portfolio landlords who want low maintenance.

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4. Best Smart Option: Google Nest Protect

Manufactured by Google

The Nest Protect combines smoke and CO detection with smartphone alerts.

Features:

• WiFi connectivity
• App notifications
• Self-testing sensor
• Voice alerts

Pros

• Smart alerts
• Premium design
• Dual detection

Cons

• Expensive
• Overkill for basic rentals

Best for: High-end homes or HMOs.

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5. Best Value Alternative: X-Sense CO03D

X-Sense has grown in popularity due to affordability.

Features:

• Digital display
• Replaceable batteries
• 10-year sensor
• EN50291 compliant

Pros

• Affordable
• Modern design
• Good reviews

Cons

• Brand less established in UK

Best for: Cost-conscious buyers.

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What To Look For When Buying a CO Alarm

1. Certification

Ensure it meets EN50291 UK standards.

2. Battery Type

• Sealed 10-year battery = low maintenance
• Replaceable battery = cheaper upfront

3. Display

Digital screens show ppm (parts per million) levels.

4. Lifespan

Most sensors last 7–10 years.

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Where Should Carbon Monoxide Alarms Be Installed?

In the same room as:

• Boilers
• Gas appliances
• Solid fuel appliances

Mount:

• At least 15cm from ceiling (wall mounted)
  OR
• Ceiling mounted at least 30cm from wall

Avoid:

• Bathrooms
• Directly next to boilers
• Kitchens

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Frequently Asked Questions

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Final Verdict: Which Should You Choose?

Best overall: Kidde 10LLCO
Best for landlords: Aico Ei208
Best budget: FireAngel CO-9X
Best smart option: Nest Protect

For most UK rental properties, a 10-year sealed battery model offers the best balance of cost and compliance.