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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Hannah
Louisville, US
★★★★★ 5
Non greasy, not much white cast compared to other mineral sunscreens
Size: 5 Fl Oz (Pack of 1)
The only one my 13 yr old will tolerate. Its the least greasy feeling of any mineral sunscreen we've tried. At 19% zinc oxide, I'm happy. Its also the least "white" cast of any we've tried. My Fitzpatrick III daughter is happy about that
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 18, 2026
R
Verified Purchase
remama
San Leandro, US
★★★★★ 3
Liked the old formula more :/ very drying
Size: 5 Fl Oz (Pack of 1), Size: 5 Fl Oz (Pack of 1)
We have used this for the longest time because me and my middle child have an allergy to chemical sunscreens. I remember last summer the formula was slightly more greasy but I preferred that. While I do like how protected my skin is (we haven’t burned at all even with the new formula, even after swimming for hours and not reapplying) it is extremely drying to where my skin looks like it’s cracking and feels very hard to wash off. Like I can still feel it on my skin after showering. May try a different one :/ super bummed! I feel like it is also hard to rub on skin because it absorbs so fast.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 30, 2026
E
Verified Purchase
Eric
Cuba, US
★★★★★ 5
Great product, not the best packaging
Size: 5 Fl Oz (Pack of 1)
Glad I got this. Just returned from a two-week dive trip in the Caribbean. Lots of sun of course! I applied this product on my face and neck prior to first and 2nd dives - I never burned. I'm fair skinned but not a magnet for sun burns. I did not have a prior base that I can speak of. The product works well, and blends into your skin fairly quickly, avoiding the white out from other mineral products. Downside - the container has some type of flow restriction. This had the effect of periodically not letting product out and then spurting out all of a sudden. Not sure if a dud, but except for that I would say absolutely I'd buy again.
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Reviewed in the United States on May 25, 2025
J
Verified Purchase
Jessica2049
Pawtucket, US
★★★★★ 5
Perfect Travel Size TSA approved size
Size: 3 Fl Oz (Pack of 2), Style: SPF 50
I recently bought the Coppertone SPORT Sunscreen SPF 50 Lotion in travel size for my son’s first trip to Cancun alone, and I have to say, it was a fantastic choice! Whether you're headed to a sunny beach, a day of fishing, or just need reliable protection from the sun, this sunscreen delivers. Here’s my review based on its performance during the trip: Convenience and Travel-Friendly: The travel size is perfect for anyone on the go. It’s small enough to meet TSA guidelines for carry-ons, so you don’t have to worry about checking luggage or dealing with oversized bottles at security. My son was able to easily pack it in his carry-on without any hassle. Additionally, the compact size makes it super convenient to throw into a pocket or backpack for a day of fishing, beach trips, or any outdoor adventure. Sun Protection: The SPF 50 provides excellent protection from harmful UVA and UVB rays, which is especially important for long hours spent in the sun. Cancun’s sun can be intense, and my son was out in the elements for several hours each day (and I wasn't there to remind him to reapply sunscreen), whether he was fishing, swimming, or just relaxing at the beach. He didn’t get burned once!! As a mother of a redheaded 18 year old son I've spent the past 18 years of my life ensuring he wasn't scorched by the sun and Coppertone has yet to let us down! Water Resistance: The water-resistant formula is a huge plus, especially in places like Cancun, where you’ll likely be in and out of the water. My son spent plenty of time swimming and snorkeling, and the sunscreen stayed put. It lasted through sweating, splashing, and even sea water exposure without needing constant reapplication. It’s perfect for active outdoor activities, whether you're swimming, surfing, or just sweating it out in the sun. Mother approved!!
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Reviewed in the United States on November 9, 2024
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Verified Purchase
Linda NYC
Cuba, US
★★★★★ 5
Dries clear, moisturizing, silky, great value
Size: 5 Fl Oz (Pack of 1), Style: SPF 50
I have fair to light combination skin. I use this on my body, but not my face. It goes on very thick and white, but sinks into the skin lightning fast (within just a few seconds), and it becomes completely invisible. It leaves my skin moisturized and looking and feeling silky. Best body sunscreen I've ever tried. And I love that it is water resistant! I find it too heavy and moisturizing to use on my face, but people with dry skin would probably love it for the face, too. I imagine it would be fantastic for them under makeup. The price per ounce is very reasonable, making it a great value.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 5, 2026

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