SKU: 22089085520

Kidde Sentry 2x 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 2x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit Mains Powered with 9V Alkaline Battery Back-Up c/w Quick Fit BaseKidde Sentry 2x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit with 9V Battery Back Up The Kidde Sentry Alarm Kit combines two KF21 Optical Smoke Alarms and one KF31 Heat Alarm to deliver comprehensive fire detection for residential properties. Designed for mains powered installation, all alarms feature 9V alkaline battery back up and can be interconnected with up to 23 compatible Kidde FIREX alarms for reliable whole home protection. This alarm bundle

Kidde Sentry 2x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit with 9V Battery Back-Up

The Kidde Sentry Alarm Kit combines two KF21 Optical Smoke Alarms and one KF31 Heat Alarm to deliver comprehensive fire detection for residential properties. Designed for mains-powered installation, all alarms feature 9V alkaline battery back-up and can be interconnected with up to 23 compatible Kidde FIREX alarms for reliable whole-home protection.

This alarm bundle is ideal for meeting UK Building Regulations in domestic properties, providing dependable smoke detection in living areas and hallways, alongside heat detection in kitchens, garages and loft spaces.

Each alarm is supplied with Kidde’s Quick-Fit Slide-On Base for faster installation, while integrated cable management keeps wiring neat and secure. The 150mm flared base also allows for a tidy retrofit when replacing existing alarms.

Kit Contents

  • 2 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, furniture or cigarettes. Ideal for circulation 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 triggered 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 specifically designed for kitchens, garages and loft spaces where smoke alarms may be unsuitable due to steam, fumes or dust. The thermistor heat sensor delivers dependable heat detection while helping to minimise nuisance alarms.

  • Mains-powered heat alarm with 9V alkaline battery back-up
  • Thermistor heat sensor for reliable temperature detection
  • Interconnects with up to 23 Kidde FIREX alarms
  • Alarm memory identifies the triggered 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 residential properties
  • Interlinked alarms provide whole-home warning when danger is detected
  • Quick-Fit bases for fast and clean 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 carried out 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
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  • 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: 22089085520

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Alex Thrace
New York, US
★★★★★ 5
Highly effective
I typically take Vitamin D in large amounts to get enhanced benefits for bone strength and immune strength. this formulation includes vitamin K which enhances the absorption of calcium in your system. These are high strength capsules with 5000 units of D in a small and easy to swallow capsule. As with any vitamin product it takes some time for the benefits to be felt however with these products they seem to have better effectiveness than my previous brand and I find myself not having to take as much to get the full benefit. The price is good for a premium product and the developers seem to have put a lot of thought into the formulation. I am fussy about my supplements and always buy the best that I can find. The known benefits of Vitamin D are many and it is essential for your good health. Yes, you can get slightly cheaper D capsules in Costco but that is false economy, as overall it will take more to get the same benefit. I love this company and all their products are top-shelf. Don't shortchange your health. I will buy these again.
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Reviewed in the United States on December 19, 2019
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Lucy
San Leandro, US
★★★★★ 5
Great product
Size: 60 Count (Pack of 1)
Great value, great quality, very happy with my purchase.
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Reviewed in the United States on March 3, 2026
R
Verified Purchase
Rose of Washington Square
Draper, US
★★★★★ 5
Helpful for my requirements
Size: 60 Count (Pack of 1)
Easy to swallow
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on March 10, 2026
J
Verified Purchase
Jackie and Art
Birmingham, US
★★★★★ 5
Superior product
typically take Vitamin D in large amounts to get enhanced benefits for bone strength and immune strength. this formulation includes vitamin K which enhances the absorption of calcium in your system. These are high strength capsules with 5000 units of D in a small and easy to swallow capsule. As with any vitamin product it takes some time for the benefits to be felt however with these products they seem to have better effectiveness than my previous brand and I find myself not having to take as much to get the full benefit. The price is good for a premium product and the developers seem to have put a lot of thought into the formulation.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 12, 2020
R
Verified Purchase
Ron
Massapequa, US
★★★★★ 4
Dentist recomended
So i ordered this a while back but i wanted to use up my last bottle of D3 vitamin. I have used this smarter nutrition brand for just under a week, so it is a bit difficult to say whether this product is any better than any other brand. But so far so good. I have no problems swallowing these pills nor any digestive problems whatsoever or any after taste. AS far as a D3 supplement, you really feel no difference and i bring this up because i am being truly honest about this product. I started taking vitamin D3 products because my dentist, who is also a nutrionist, advised me to take this supplent for stronger bones. Also to be honest, I am 67 years young and i need all the help i can get..LOL. I take many other nutritional products and this brand of Smart seems to have everything i need for a daily regimen. So No need to buy supplements from more than 1 supplier. And, yes i guess i would recommend this brand to others who like to buy what they need from 1 supplier.
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Reviewed in the United States on October 29, 2019

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