SKU: 18187191542

Kidde Sentry 1x 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 1x KF21 Optical Smoke & 1x KF31 Heat Alarm Kit Mains Powered with 9V Alkaline Battery Back-Up c/w Quick Fit BaseKidde Sentry KF21 & KF31 Mains Powered Smoke and Heat Alarm Kit with 9V Battery Back Up The Kidde Sentry Alarm Kit combines the reliable KF21 Optical Smoke Alarm and KF31 Heat Alarm to provide comprehensive fire detection throughout residential properties. Designed for mains powered installation, both alarms feature 9V alkaline battery back up protection and can be interconnected with up to 23 compatible Kidde FIREX alarms for complete home safety

Kidde Sentry KF21 & KF31 Mains Powered Smoke and Heat Alarm Kit with 9V Battery Back-Up

The Kidde Sentry Alarm Kit combines the reliable KF21 Optical Smoke Alarm and KF31 Heat Alarm to provide comprehensive fire detection throughout residential properties. Designed for mains-powered installation, both alarms feature 9V alkaline battery back-up protection and can be interconnected with up to 23 compatible Kidde FIREX alarms for complete home safety coverage.

This convenient alarm combination is ideal for meeting UK Building Regulations in domestic properties, offering dependable smoke and heat detection across living spaces, hallways, kitchens, garages and loft areas.

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 provides a tidy finish when replacing existing alarms.

Kit Contents

  • 1 x Kidde KF21 Optical Smoke Alarm
  • 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 furniture, electrical faults and cigarettes. Ideal for escape routes and living areas, the alarm 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 triggered unit
  • 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 ideal for kitchens, garages and loft spaces where smoke alarms may be affected by steam, cooking fumes or dust. The thermistor heat sensor provides reliable temperature detection without 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 triggered unit
  • Combined Test/Hush button
  • Auto reset after activation
  • Tamper-resistant locking mechanism
  • Ideal for kitchens, garages and humid environments
  • BSI certified to BS 5446 Part 2:2003
  • 10-year warranty

Key Benefits

  • Complete smoke and heat detection 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 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: 18187191542

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4.6 ★★★★★
Based on 16 reviews
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Product Reviews
C
Verified Purchase
Camryn
Pawtucket, US
★★★★★ 5
Great Chair! Worth the Price!
Color: Sky Blue, Size: Pack of 1
LOVE my new desk chair! I got the Sky Blue which is a really pretty blue in person. I work from home in tech, and had been getting constant headaches no matter what position I was in. I finally decided to invest in a better desk chair, and I'm SO glad I did! It's much more supportive and comfortable. I really like that I can flip the arms up or down, and the height is easy to adjust. Also, because I can flip the arms up, I can keep the chair out of the way when I'm not working by putting it right up against the desk. Very much worth the price! Assembly was simply and quick. Not even 30 minutes. Also, when I had a question about the chair, their support team was quick to respond and very helpful. Highly recommend!
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 2, 2026
D
Verified Purchase
David Miller
Whiting, US
★★★★★ 5
Great quality chair, regardless of price.
Color: Black+white, Size: Pack of 1, Color: Black+white, Size: Pack of 1
Great quality chair, regardless of the price, period. So well packaged that it took almost as long to unwrap as assemble. Assembly was easy (loved the Allen wrench with sturdy handle). I am 6'2" and the fit and height adjustments work well for my height. Comfort is personal, so I like the semi-firmness of the seat. While the chair is constructed of heavy gauge plastic the base is solid metal with enamel finish: I love the look. The arm rests line up perfectly to my computer keyboard. I expect many, many years of service.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 17, 2026
E
Verified Purchase
EJ
Battle Creek, US
★★★★★ 5
Great Value for a Comfortable Home Office Chair
Color: Black, Size: Pack of 1, Color: Black, Size: Pack of 1
I’ve been using this chair for a couple of days now, and honestly, it’s been a solid upgrade from my old one. I work from home most days, so comfort matters a lot—and this chair delivers better than I expected for the price. The first thing I noticed was the lumbar support. It’s actually adjustable and makes a noticeable difference, especially if you tend to sit for long stretches. My lower back used to get sore after a few hours, but that hasn’t really been an issue since switching to this chair. The mesh back is also a nice touch—it keeps things breathable, which I didn’t think I’d care about until I had it. Assembly was pretty straightforward. Took me maybe 20–25 minutes without any frustration. Everything lined up well, and the instructions were clear enough. In terms of comfort, the seat is firm but not hard. It doesn’t feel like one of those super plush chairs, but I actually prefer that because it feels more supportive over time. The reclining feature is smooth, and I like that you can lean back a bit when you need a break. Overall, I’d say this is a great value for a home office setup. If you want something ergonomic and comfortable without spending a fortune, this chair is definitely worth considering.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on April 30, 2026
A
Verified Purchase
Amazon Customer
Alexandria, US
★★★★★ 5
Excellent Office Chair
Color: Black+white, Size: Pack of 1
I just received my TRALT Office Chair. First of all, I was impressed with the packaging of this item. When I opened the box each piece of the chair was wrapped in plastic or bubble wrap. Everything in the box arrived safely and without damage. Secondly, the instructions to assemble the chair were very each to follow. I was impressed with the Allen wrench which had a handle attached to it. This made screwing in the screws very easy. I was able to assemble the chair without any difficulty. Lastly, the look of the chair and the comfort is exceptional. I ordered the black/white chair which looks amazing. The comfort of the chair is really excellent. My back is supported by the lumbar seat and having the armrests being able to go up when not needed is wonderful. The quality of the chair is definitely worth the price.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on May 9, 2026
J
Verified Purchase
Jennifer3002
Port Orchard, US
★★★★★ 4
a good choice
Color: Black, Size: Pack of 1, Color: Black, Size: Pack of 1
Assembled chair only to find that the lift cylinder was faulty. Would have preferred to be able to just get a replacement cylinder but calling China didn't seem like a viable option. Guessing which one & buying it online would involve paying for a good portion of what the chair cost. Customer service could only offer a replacement or refund. We're disassembling (so much fun?!) to send it back. The chair itself was very comfortable, assembled fairly easily and instructions pretty clear. Again, if we could only have asked the seller for the replacement part......**Update**...Or if the instructions that seemed so clear were clearer!, as we started to disassemble, we decided to see what would happen if the tension knob (see photo) was loosened. IT ALLOWED THE LIFT CYLINDER TO WORK. Not at all what the instructions say. At any rate, we're keeping the chair.
WAS THIS REVIEW HELPFUL?YesReportShare
Reviewed in the United States on June 4, 2026

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