In my question Detecting spoiled food in a refrigerator, I am asking for a sensor to detect spoiled food in a refrigerator, so that I can build a little gadget to detect it and alert me.

There are various sensors available that detect different gases, which I imagine would be the way to approach the project.

However, I don't know what gas(es) I would want to detect. The good folks on h/w recommendations might also not know, but, given the name of the gas(es), they could help me source the sensor(s) needed, or I could search for myself.

Question: would it be on topic for this site if I were to ask which gases are produced by spoiled food?

1 Answer 1


While your question is quite unusual for us, I don't think it will be a problem when it comes to site scope. We do answer questions on food safety, nutrient-composition, and food chemistry, so I guess we could stretch it to the chemical composition of decaying food.

The problem is that you will likely run afoul of the rules that the question has to be suitable for a Stack Exchange site. Your current wording requires book-length answers, which is not feasible. You would have to really focus your question, probably by picking a single food type and a single decay mechanism for the question. In fact, from an engineering perspective, it is probably much easier to tackle and solve a single problem before generalizing to everything.

The tricky part is that, for picking what you focus on, you will have to do so much preliminary research, that you might soon know more than we do. Picking at random may lead you to a bad choice - to take one clear-cut example, you probably don't want to start with the detection of moldy fruit, because 1) normal air mold loads differ between kitchens, and in each kitchen with time of season, and 2) you may a different sensor for detecting airborne mold particles than for gas molecules. But then again, until you know enough about each decay mechanism to decide which ones are worth starting with, you probably won't need to ask the question.

It is also a problem to ask "which one is optimal to start with", because it is likely that there are many optimal ones, making it a big-list question without a single objective answer, which is again not a SE-suitable question.

If you can think of other formulations or options, you can still run them here by us, or in chat, and we can see if one fits.

  • Thank you very Much., For such a quick, and detailed, answer. "The tricky part is that, for picking what you focus on" - hmmm, well, we can rule out fruit & eggs, as those never go in the fridge. It is mostly meat, veg and occasionally yoghurt. Do you think that asking for those 3 would be too much? Or 3 separate questions? Or asking which foods spoil quickest (not prefect, as foods go in at different times, but detecting the quickest culprit might help). Or any other way to get it on topic.? -->
    – Mawg
    Commented Nov 18, 2021 at 7:18
  • --> I am not thinking of a commercial product here, so it doesn't need to be 100% accurate, just a way to give me a gentle nudge to check out the fridge - before my nose tells me to :-)
    – Mawg
    Commented Nov 18, 2021 at 7:19
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    Even one of these food groups would be too much for one question. Each food can spoil through dozens of different microorganism species, and each of these species will produce a different gas signature. You would have to pick one combination of food and microorganism species to start. Hopefully someone will be able to name some gases for that combination, you can find sensors for those, and then your hard work starts. While developing the detector for the first combo, you will probably amass so much knowledge on food pathogen microbiology, that you won't have to ask us for a second combo.
    – rumtscho Mod
    Commented Nov 18, 2021 at 8:06
  • Lolx ! I like that last part. It's only a hom eproject, so I will take an ESP32 which I have lying around & knock up some code. In parallel, when I can drag myself away from S.E, Reddit & online gaming, I will do some research. If I do, as you say "amass so much knowledge on food pathogen microbiology", then maybe there actually is a commercial product in it. These probably exist at industrial level, which might give me ideas, but I haven't seen one for home use. Otoh, as with so much else, I am likely to start filled with enthusiasm and abandon it when the next enthusiasm strikes :-)
    – Mawg
    Commented Nov 18, 2021 at 8:56

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