John Lewis CO400 Carbon Monoxide Alarm


John Lewis
Eligible for International Delivery
Power supply
Includes 2x AA batteries

Product information

The John Lewis CO400 alarm will provide basic protection from the threat of carbon monoxide. It uses a loud 85dB alarm and there’s a Test and Silent button and a low battery warning.

Where to place your alarm: One on every level of the home and one in each bedroom.

Note: This product is intended for domestic use. It is not desiged to measure CO levels in compliance with Occupational Health and Safety Administration (OSHA), commercial or industrial standards. Individuals with medical conditions may consider warning devises which provide audible and visual signals for CO under 30ppm. All John Lewis Alarms conform to regulatory requirements including UL2034.


  • Click & collect

    Click & collect from John Lewis and Waitrose shops tomorrow from 2pm
    Find out more
  • Collect+

    Collect + from a local shop from Tuesday, postcode exclusions apply
    Find out more
  • UK delivery

    Standard delivery within 5 working days
    Named or Saturday UK delivery
    Named day UK delivery pre-10.30am
    Find out more
  • International delivery not available


We want you to be happy with your purchase. If you're not, depending on the type of product, you can make free returns in the UK via John Lewis shops, Royal Mail, Collect+, or MyHermes. If you need to arrange collection of large or heavy items, call us on 03456 049 049. For international returns queries, call us on +44 1698 545 454. Find out more about returns.

You'll find returns information on your delivery note. Unless faulty, we'd like you to make your return within 90 days of purchase. Exceptions apply to certain products - find out more about our refund policy.

Q & As

Rated 3.8 out of 5 by 5 reviewers.
Rated 5 out of 5 by Seems to be ok. Yeah nice little product, just put the batteries in and hopefully its working. I have put it next to the boiler for about a month now and nobody is suffering from CO poisining indicating that it is working. Battery powered so doesnt use up a socket as well. 10 November 2015
Rated 1 out of 5 by Shame About the Battery Cover I purchased one of these click & collect last week and drilled the new set of holes as it didn't match the fittings for our old alarm. I fitted it on the wall, inserted the batteries, closed the flap and it fell straight back down again. I realised that the catch was broken so rang customer services and arranged for a replacement. When I took that one out of the packaging, the catch was already broken. As I have no room for any more holes in the wall for a different alarm, I tried another replacement, this time checking it in the store when I collected it, but once again it was broken. The fourth one sent out was initially ok, but when I fitted the batteries and closed the flap, the catch immediately broke off. I have now fitted it using Blu Tack to hold the flap in place. I am assuming that the alarm function itself will be ok, but I am very disappointed that the design of the battery cover is so poor. 28 August 2015
Rated 4 out of 5 by Negative is positive In common with many other successful safety devices, it is hard to tell how good it is. You can have one for years, and the only indication that it is working is that it tells you when the batteries need to be replaced - or indeed the device itself. If there is no CO to detect, it will not detect it. Quite probably, it is the sort of device that is bought only by people who take health and safety seriously, so equally probably have their appliances checked and maintained scrupulously. If nothing has gone wrong, there is nothing to detect. All we can assume – since we're alive and have suffered no symptoms of CO poisoning – is that it would have worked if it had needed to, as, we assume on the same basis, would the one it replaced. 23 June 2015
Rated 4 out of 5 by Easy to install Easy to follow instructions & very simple to install. 18 December 2012
Rated 5 out of 5 by JL CO400 Caron Monoxide Alarm Easy to find on JL website. Fast delivery to Waitrose Cirencester - polite and efficient pick up. Pleasant experience - hassle free. 25 April 2012
  • 2015-12-15 T15:59:38.618-06:00
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