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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4.6 ★★★★★
Based on 1178 reviews
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R
Verified Purchase
Rob
Port Orchard, US
★★★★★ 4
Tough toy, but the yellow tire broke at the seam
Size: 10.5 inch Rubber Flex Tread
It was fun while it lasted and it got a lot of use, but it finally gave out after 6+/- months? Great tug toy. My dog is a 70# mutt with a strong bite and he's chewed through pretty much every other toy he's ever had. This one lasted longer than any of the others by quite a bit. He did zero chew damage to the tires, but the yellow tire in the middle broke at the seam. No tear, the seam just came undone at 90 degree angles. I'm going to look for something else this time but this wasn't bad considering how long it lasted and it wasn't very expensive. If I don't find anything tougher, I may purchase another one of these down the road.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 18, 2024
J
Verified Purchase
JB
Waukegan, US
★★★★★ 1
Not for tough chewers at all!!!
Size: 10.5 inch Rubber Flex Tread, Size: 10.5 inch Rubber Flex Tread
5 minutes in and it's destroyed. Very disappointing.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 21, 2026
N
Verified Purchase
Nicky S
Pawtucket, US
★★★★★ 5
Great chew toy
Size: 10.5 inch Rubber Flex Tread
This is my second time buying the Tonka rings. My dog loves this chew toy. It does take him a bit to destroy them. I give this toy to him as a reward otherwise it be destroyed in 3 days. I have a pitty. So other dogs it should last longer. They are shin whackers and hurt when they connect. So I make sure to watch the dog and toy around small kids and elderly to be safe. They are heavy and made well.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on October 29, 2025
A
Verified Purchase
Ann
Cuba, US
★★★★★ 5
Finally a toy we can leave out!
Size: 10.5 inch Rubber Flex Tread, Size: 10.5 inch Rubber Flex Tread
There are very few toys that we can leave out for our 11 month old golden. Which is a shame because as a small puppy, we taught him to bring us a toy to initiate play instead of nipping. Ropes or stuffies never lasted more than a few minutes so they always had to be taken away. One time he brought us a benenbone to play tug. So I tried this as a last resort. Finally something we can keep out for him! It’s not completely indestructible. He has figured out how to pull bits of tread off. But he chewed hard on it for a solid 20 minutes and it’s still intact with the exception of a few small tread pieces. Can’t say that for 99% of the other dog toys on the market! UPDATE: OK, so it's definitely not indestructible. After a few days of dedicated gnawing, he has almost chewed through the yellow ring so we can't leave him too unsupervised with it. I'm still going to leave it as 5 stars since it's the best tug toy that I have found so far and we have tried a lot! I may buy another one and just make sure I don't let him freely chew on it for any length of time.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 1, 2023
E
Verified Purchase
eave4sean
Carnegie, US
★★★★★ 3
Really wanted this toy to be better...
Size: 10.5 inch Rubber Flex Tread
I got this toy because I have 3 large dogs that all like to pull things. I can't always play with them even though they follow me everywhere wanting to play, so I saw this toy and thought it would be good because it would give them something they can tug away at with each other. I saw the thick rubber and thought it would last awhile, but I was wrong. My German Shepherd and Pyrenees mix chewed though the first tire rather quick, and before I realized, I was finding chunks of tire around the house and yard. Thankfully, none of them tried to eat it. It seems like it could be a good toy for an aggressive chewer IF they are smaller and not as strong as these large dogs are, but it did not hold up long to mine.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on November 23, 2024

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