SKU: 49395378060

Kidde Sentry 4x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit Mains Powered with 9V Alkaline Battery Back-Up c/w Quick Fit Base

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Description

Kidde Sentry 4x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit Mains Powered with 9V Alkaline Battery Back-Up c/w Quick Fit BaseKidde Sentry 4x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit with 9V Battery Back Up The Kidde Sentry Alarm Kit includes four KF21 Optical Smoke Alarms and one KF31 Heat Alarm, providing a complete mains powered fire detection solution for larger residential properties. Designed to deliver reliable smoke and heat detection throughout the home, each alarm features a 9V alkaline battery back up and can be interconnected with up to 23 compatible Kidde

Kidde Sentry 4x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit with 9V Battery Back-Up

The Kidde Sentry Alarm Kit includes four KF21 Optical Smoke Alarms and one KF31 Heat Alarm, providing a complete mains-powered fire detection solution for larger residential properties. Designed to deliver reliable smoke and heat detection throughout the home, each alarm features a 9V alkaline battery back-up and can be interconnected with up to 23 compatible Kidde FIREX alarms.

This interlinked alarm system ensures that when one alarm detects danger, all connected alarms sound simultaneously, helping to provide earlier warning and improved occupant safety across multiple rooms and floors.

Each alarm is supplied with Kidde’s Quick-Fit Slide-On Base for faster installation and includes integrated cable management to maintain neat, secure wiring. The 150mm flared base plate also provides a clean retrofit finish when replacing existing alarms.

Kit Contents

  • 4 x Kidde KF21 Optical Smoke Alarms
  • 1 x Kidde KF31 Heat Alarm

KF21 Optical Smoke Alarm Features

The Kidde KF21 optical smoke alarm is ideal for detecting slow, smouldering fires caused by electrical faults, furniture or cigarettes. Suitable for escape routes and living spaces, the optical sensor provides dependable early warning protection.

  • Mains-powered optical smoke alarm with 9V alkaline battery back-up
  • Optical sensor with dust compensation and bug screen
  • Interconnects with up to 23 Kidde FIREX alarms
  • Alarm memory identifies the activated alarm
  • Combined Test/Hush button
  • Auto reset after activation
  • Tamper-resistant locking mechanism
  • Suitable for hallways, bedrooms, lofts and living areas
  • BSI certified to BS EN14604:2005
  • 10-year warranty

KF31 Heat Alarm Features

The Kidde KF31 heat alarm is designed for kitchens, garages and loft spaces where smoke alarms may be unsuitable due to steam, dust or cooking fumes. Its thermistor heat sensor provides reliable temperature detection while helping reduce nuisance alarms.

  • Mains-powered heat alarm with 9V alkaline battery back-up
  • Thermistor heat sensor for dependable heat detection
  • Interconnects with up to 23 Kidde FIREX alarms
  • Alarm memory identifies the activated alarm
  • Combined Test/Hush button
  • Auto reset after activation
  • Tamper-resistant locking mechanism
  • Ideal for kitchens, garages and loft spaces
  • BSI certified to BS 5446 Part 2:2003
  • 10-year warranty

Key Benefits

  • Complete smoke and heat alarm solution for larger homes
  • Interlinked alarms provide whole-home warning when danger is detected
  • Quick-Fit bases for fast and efficient installation
  • Integrated cable management for tidy wiring
  • Suitable for compliance with UK Building Regulations
  • Grade D domestic fire alarm system solution
  • Fully compatible with Kidde FIREX smoke, heat and CO alarms

Technical Specifications

KF21 Optical Smoke Alarm

  • Model: KF21
  • Power Supply: 230V mains with 9V alkaline battery back-up
  • Sensor Type: Optical
  • Alarm Volume: 85dB minimum at 3 metres
  • Dimensions: 150mm x 53mm
  • Weight: 295g
  • Operating Temperature: -10°C to +40°C
  • Warranty: 10 Years

KF31 Heat Alarm

  • Model: KF31
  • Power Supply: 230V mains with 9V alkaline battery back-up
  • Sensor Type: Thermistor heat sensor
  • Alarm Volume: 85dB minimum at 3 metres
  • Dimensions: 150mm x 150mm x 66mm
  • Weight: 281g
  • Operating Temperature: -10°C to +40°C
  • Warranty: 10 Years

Please Note: Alarms are supplied individually within the kit. Installation should be completed by a qualified electrician.

Downloads

KF21 Data Sheet:
Download KF21 Data Sheet

KF31 Data Sheet:
Download KF31 Data Sheet

KF21 Instruction Manual:
Download KF21 Instruction Manual

KF31 Instruction Manual:
Download KF31 Instruction Manual

Shipping Notes
  • Free Standard Shipping on $100+ Orders to the USA.
  • Except Preorder products are shipped in 48 hours.
  • Delivery to the USA:
  1. Standard Shipping : 3-10 business days
  • If time is of the essence, please consider selecting expedited delivery for faster service.
Exchange/Return Notes
  • We offer a 30-day return/exchange service after receiving.
  • Final sale items are not eligible for returns or exchanges.
  • To process your return/exchange, please contact us at [email protected]
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SKU: 49395378060

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Verified Purchase
Dave Wright
Houston, US
★★★★★ 5
STA-BIL Start Your Engines! Because Sometimes Engines Need a Pep Talk
Size: 2 fl oz
So, STA-BIL Start Your Engines! is basically that friend who shows up uninvited but actually saves the day. You know, the one who doesn’t ask questions and just gets your engine running when it’s feeling moody or sluggish. Does it work? Of course it does. Like, “put a little in your gas tank, say a quick prayer, and voila!” kind of work. Suddenly your car remembers how to start, and you feel like a mechanic genius without actually lifting a wrench. It’s simple, it’s reliable, and it doesn’t judge you for letting your gas sit around until it gets that “I don’t want to cooperate” attitude. Pros: Makes your engine start like it just had an espresso shot. Easy to use — even if you’re barely awake in the morning. No weird smells or smoke signals, just clean, smooth starting. Cons: Won’t fix your “I forgot to put gas in” problem. Sadly, can’t make your car drive itself to work (yet). You might start relying on it a little too much — hey, no judgment. Final Verdict: ⭐️⭐️⭐️⭐️⭐️ – 5 stars. If your engine is feeling lazy, this stuff just works. It’s like a pep talk in a bottle for your car. Highly recommended for anyone who’s ever cursed their ignition.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on October 17, 2025
N
Verified Purchase
Nobody
Waukegan, US
★★★★★ 5
GREAT PROPDUCT
Size: 2 fl oz
EXCELLENT
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on January 27, 2026
A
Verified Purchase
Amazon Customer
Charlottesville, US
★★★★★ 4
Cleans Out Working Carburetors
Size: 2 fl oz
I recommend this product for engines that will in fact start but not run well. I highly recommend it for that specific purpose, which it is designed for. It cleans the inner workings of the carburetor. Of course, you will have a cleaner carburetor if you take it apart and clean it with proper tools and a proper carburetor cleaner. You spray it in the gas tank, start the engine, and let it run a bit. It will not start an engine with a totally plugged up carburetor. Nothing is going to do that. Nor is it a fuel stabilizer, as one previous reviewer seemed to think. Nor is it a product to be used to bring life back to stale gasoline, as another reviewer seemed to think. The only thing to do with stale gasoline is drain it out and pitch it. Nor is it a product to be used for cleaning a carburetor you have taken apart to clean. You should use a proper carburetor cleaner for that purpose. I've given it four stars because it cleans out mildly plugged up carbs. It is not a miracle solution for really neglected carbs as the name suggests.
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Reviewed in the United States on April 12, 2020
R
Verified Purchase
Ray
New York, US
★★★★★ 5
Helps fixing small engines
Size: 2 fl oz
⭐⭐⭐⭐⭐⭐⭐
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 16, 2026
J
Verified Purchase
JustAGeek
Fort Morgan, US
★★★★★ 5
It works like magic, saved me $150.
Size: 2 fl oz
I filled 1/4 tank of gas into my snowblower which I could not started, sprayed about 15 seconds of Start Your Engines, rock snowblower to mix well, let it sat for an hour. I pulled string and yet couldn't start engine. Unscrewed spark plug and spray some into cylinder, put the spark plug back and pull the string. ENGINE STARTED!!! SAVED ME AT THE LEAST $150.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 1, 2026

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