Kidde Sentry 3x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit Mains Powered with 9V Alkaline Battery Back-Up c/w Quick Fit Base
SKU: 55425022656

Kidde Sentry 3x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit Mains Powered with 9V Alkaline Battery Back-Up c/w Quick Fit Base

$91.19 $101.32
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Description

Kidde Sentry 3x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit Mains Powered with 9V Alkaline Battery Back-Up c/w Quick Fit BaseKidde Sentry 3x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit with 9V Battery Back Up The Kidde Sentry Alarm Kit combines three KF21 Optical Smoke Alarms and one KF31 Heat Alarm to provide comprehensive fire detection coverage throughout residential properties. Designed for mains powered installation, each alarm features a 9V alkaline battery back up and can be interconnected with up to 23 compatible Kidde FIREX alarms for complete whole home

Kidde Sentry 3x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit with 9V Battery Back-Up

The Kidde Sentry Alarm Kit combines three KF21 Optical Smoke Alarms and one KF31 Heat Alarm to provide comprehensive fire detection coverage throughout residential properties. Designed for mains-powered installation, each alarm features a 9V alkaline battery back-up and can be interconnected with up to 23 compatible Kidde FIREX alarms for complete whole-home protection.

This alarm bundle is ideal for larger homes and multi-room residential properties, offering dependable smoke detection in hallways, landings, bedrooms and living areas, alongside dedicated heat detection for kitchens, garages and loft spaces.

Each alarm is supplied with Kidde’s Quick-Fit Slide-On Base for fast and tidy installation. Integrated cable management helps maintain organised wiring, while the 150mm flared base ensures a clean finish during retrofit installations.

Kit Contents

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

KF21 Optical Smoke Alarm Features

The Kidde KF21 optical smoke alarm is designed to detect slow, smouldering fires commonly caused by electrical faults, upholstery or cigarettes. Ideal for escape routes and living spaces, the KF21 provides reliable 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 rooms
  • 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, cooking fumes or dust. The thermistor heat sensor provides dependable heat detection while helping reduce nuisance alarms.

  • Mains-powered heat alarm with 9V alkaline battery back-up
  • Thermistor heat sensor for reliable 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

  • Comprehensive smoke and heat alarm solution for larger homes
  • Interlinked alarms provide whole-home warning when danger is detected
  • Quick-Fit bases for fast and simple installation
  • Integrated cable management for neat 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]
  • Please click here for more details>>> Return & Exchange Policy
SKU: 55425022656

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P
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phan_graph
Pawtucket, US
★★★★★ 4
Great buy
Color: Blue+Red
My dogs kill every toy. They arrived very agressive chewers. These have lasted way longer than most balls have. Great value
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 24, 2026
M
Verified Purchase
megs2168
San Leandro, US
★★★★★ 5
If your dog loves tennis balls, you NEED these
Color: Azure+Orange, Color: Azure+Orange
Raising any puppy is tough. Raising a German Shepherd puppy has often left me questioning my life choices. So I was ecstatic the day that my 60-lb puppy decided that he loves tennis balls and occupied himself for 2 hours without needing constant intervention. Naturally, my immediate response was to make sure we had a constant supply of large tennis balls for dogs available. Now my puppy loves mischief, but he’s not an aggressive chewer. And I was irritated to discover that every brand and size of tennis ball broke within an hour max of play. By simply playing fetch and batting the ball around with his paws, every single tennis ball split into 2 halves. We needed something better! These squeaky balls are exactly that! They come in a 2-pack. I gave my pup the 1st one a week ago and it’s still going strong! We play fetch in the backyard, he brings it into the doggy pool with him, it rolls around in the dirt and can be rinsed off easily. It’s by far his favorite toy, and he takes it everywhere with him. Finally a squeaky ball that can keep up with my dog! These are the perfect size, texture, bounce, squeak, everything. These are the ONLY squeaky balls I will buy from now on. Five stars for sure!
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 12, 2026
B
Verified Purchase
Brad
Cuba, US
★★★★★ 5
Really are indestructible. Amazing product.
Color: Blue+Red
Wow! Really indestructible. Our large dogs have destroyed other “indestructible” toys in less than an hour and these are amazing. They squeak, which our dogs love (we hate) and they float when they go into our pool. IF they ever do wear out or are lost I will definitely buy again.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 3, 2026
K
Verified Purchase
Kelsey
Lowell, US
★★★★★ 5
Durable squeaky ball for chewers
Color: Blue+Red, Color: Blue+Red
These are great! My 54 lb GSP loves them and it’s the only thing she cannot destroy! She’s currently 1 year and we have had the balls for several months. We have this brand and similar ones too. They float, bounce, and squeak. The ridges are good for chewing.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 4, 2026
S
Verified Purchase
Stephanie Dutey
Los Angeles, US
★★★★★ 5
Finally a Toy My Pitbull Hasn’t Destroyed in 5 Minutes
Color: Blue+Red, Color: Blue+Red
I have a 65 lb pitbull who destroys most toys almost immediately, so I’m always skeptical when products claim to be “indestructible.” Most toys last maybe a few minutes in my house before pieces are everywhere. These have actually held up surprisingly well. The material feels durable and thick enough to handle really aggressive chewing, and so far my dog hasn’t been able to destroy them like he does with most other balls and squeaky toys. That alone makes these worth it to me. I also really like the size. They’re large enough that I don’t have to constantly worry about him accidentally swallowing them or choking while playing, which is a huge plus for bigger dogs. The squeaker inside also keeps him interested longer since he usually gets bored quickly with toys that don’t make noise or bounce around well. If you have a strong chewer or larger dog and you’re tired of replacing destroyed toys constantly, these are definitely worth trying.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 10, 2026

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