I turned my oven down to around gas mark 3 last night while I finished the rest of dinner. After taking the food out of it, I accidentally left it on for about 5 hours overnight.

Our CO meter didn't go off, and I've turned the oven off now.

Besides having switched the oven off (if it wasn't obvious) is there anything I need to do to make the situation safe or prevent oven damage?

  • 1
    I set off my carbon monoxide alarm at 4am doing this in a studio apartment. That made one heck of an early alarm clock. Commented Dec 22, 2021 at 20:11
  • 7
    Make sure you sit down before you open the gas bill!
    – James D
    Commented Dec 22, 2021 at 21:40
  • 15
    @JamesD - I’ve made slow cooked ribs, 18 hours in the oven, barely noticed it on the bill. Heating the house is many time the cost of that oven. Commented Dec 23, 2021 at 2:22

2 Answers 2


No, ovens are designed to function for long periods if necessary, for example in overnight cooking. You might have some burned-on dirt that is harder to clean than usual.

I've done this before and been spooked about having a (mild) fire risk due to my own negligence; to reduce the likelihood of it happening again I try to incorporate checking the oven/hobs are off into my routine as I take the food to the table.

  • 2
    I normally do have that routine, but it failed me this time. Good to know this isn't as bad it could have been! Commented Dec 22, 2021 at 11:53
  • 15
    I make it a habit to turn the oven light on whenever the oven is on; this is a fairly obvious visual cue that I need to turn it off if it's empty. Commented Dec 22, 2021 at 20:26
  • @crash, I'm fairly sure that the light was on as well Commented Dec 23, 2021 at 3:07

Ventilate your home. Your CO detector will not detect high CO2 levels, see https://gaslab.com/blogs/articles/carbon-monoxide-carbon-dioxide-detector

Use your smartphone and set a timer/reminder to turn your oven off next time :)

  • 5
    There's no way in hell that an oven would produce dangerous CO2 levels in a house. At least not without also producing dangerous CO levels. This really is a non-concern Commented Dec 23, 2021 at 15:12
  • @Persistence: 1. Burning a given volume of natural gas will release approximately the same volume of carbon dioxide (and twice the volume of water vapour) -- that can be far from negligible for the span of 5 hours if ventilation is not sufficient. 2. Carbon monoxide emission is much much lower then that (up to 400 ppm) and becomes an issue only if the combustion is not complete because of lack of oxygen. The CO detector will only trigger if you have incomplete combustion.
    – g.kertesz
    Commented Dec 23, 2021 at 22:43
  • The only way that you could end up with the CO2 not being dispersed into the wider atmosphere is with really, really bad ventillation. In that situation, there wouldn't be enough oxygen and you'd end up producing plenty of CO. If you have enough ventillation to prevent CO buildup, CO2 buildup really isn't a problem. Commented Dec 24, 2021 at 9:52
  • @Persistence, Agreed with your first sentence. But the CO2 poisoning threshold is around 10.000 ppm = 1% when exposed for an extended period. It will bring down the O2 level from 21% to 20%, so no, not "plenty of CO" at that point. We are talking about a situation when the over is working perfectly, but over a course of >5 hours.
    – g.kertesz
    Commented Dec 24, 2021 at 12:13
  • 1
    Aye, I'm well aware of that, but you misunderstand me. There is categorically no realistic situation where an oven would be working perfectly and burn through enough oxygen to give someone CO2 poisoning without them succumbing to CO poisoning first. You'd quite literally need a hermetically sealed house. Otherwise, the CO2 is just going to diffuse perfectly happily into the environment. It's such a contrived example it's not even worth considering Commented Dec 27, 2021 at 17:45

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