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I'm currently at work and I'm having a little panic attack.

I followed a recipe that require the ribs to be wrapped in foil and cooked at 180F for 9hours. I left about 30 minutes ago and for who knows why I didn't think it could be a bad idea before, but now I'm feeling unsure and worried.

The ribs are wrapped in two layers of aluminium sitting on a baking sheet. The ribs were coated since last night in a dry rub and I've added sauce on them this morning before closing the wrapping again.

Please give me your thought.

Edit: I just wanted to give you guys an update. So by precaution I asked my boss if I could take the rest of the day off and he agreed to let me go around noon (4+ hours into cooking), a risk I had to live with.

When I got home, my house was still standing in one piece and when I opened the door the smell running through my nose was incredible. I left the ribs to cook in the oven for another 5 hours before attempting to put them on the grill of the BBQ at high setting.

The ribs were a bit too tender so I lost some in the process of grilling them, but the taste was amazing. It's the first time I manage to cook rib without boiling them first and I can honestly say I'm satisfied with the result, though I would probably cut down on the last hour in the oven.

As for the safety of this adventure, I think it would be safe to redo it unattended especially because of how low temperature is set, but as other people mentioned it is important to have a clean oven.

Happy safe cooking everyone.

EDIT 2: I have an electric oven.

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One thing not mentioned so far is the risk of fire from a dirty oven. Some people never clean their ovens, and the floor of the oven collects a large amount of grease and fat, which are of course flammable. The fire department here (in the UK) specifically mentions this as a fire risk. If you keep your oven clean (or at least not too dirty), that risk is eliminated. –  Paddy Landau Sep 30 '13 at 18:40
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Just turn off the oven and leave the door closed and it will extinguish itself promptly by using up all the available oxygen. The danger comes when people open the door to try to extinguish it or to save their food, which is exactly the wrong thing to do. Opening the door just supplies it with a nice supply of oxygen, allowing it grow into a much larger fire. –  Carey Gregory Sep 30 '13 at 18:47
    
@CareyGregory - Ovens are not air-tight, especially convection ovens (mine is certainly vented), and if the oven is unattended, how would the cook know there was a fire in the first place? You have made many unfounded or uncorroborated assertions on fire safety. Please back some of them up with documentation, and consider the real world consequences of your advice if you are actually incorrect. –  RI Swamp Yankee Oct 10 '13 at 13:34
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3 Answers 3

up vote 11 down vote accepted

Yes, there's a risk, but it's not significantly higher than having most other home appliances turned on (eg, a lamp, dehumidifier, dish washer or dryer).

Although it heats up, a full-sized oven is insulated, and you're not operating at a very high temperature. Provided it seals well, even if there's a fire, there would be little oxygen to sustain it. I would not trust a toaster oven or desktop oven. with this sort of thing, as they're not as well insulated, nor do they tend to seal well.

As ovens are based on temperature, and will cycle on an off, rather than just feed in a constant amount of power (such as a cook top) ... so it won't get so hot that it causes other issues.

Update: I made the (possibly incorrect) assumption that this was an electric oven. I don't know that I'd trust a gas oven the same way (as I would assume that it is not well sealed) ... although people leave their home heating systems and water heaters on without shutting them off when they leave each day, so it's probably not an issue.

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I would eliminate dryer from that list. Clothes driers are frequent causes of fires because people don't clean lint from the lint trap and exhaust regularly. It's the one appliance I won't leave running when no one is home. –  Carey Gregory Sep 30 '13 at 16:27
    
@CareyGregory : excellent point ... I knew some folks who moved into a shared apartment after college and couldn't figure out why their dryer no longer worked ... because they had been there for months and had never emptied it out. Dish washers are also a problem if you infrequently use them ... if it's your first time running it in 6 months, you might have dry-rotted gaskets. –  Joe Sep 30 '13 at 18:31
    
....oh, and years ago, Whirlpool put out the 'Polara' fridge/oven, so you could put your food in there in the morning (on chill), then have it start cooking so it'd be ready for you when you got home. –  Joe Sep 30 '13 at 18:38
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The Polara sounds like one of those things that sounds good but in practice turns out to be a really bad idea. –  Carey Gregory Sep 30 '13 at 18:50
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There are three issues here:

  • The quality of the food
  • The safety of the food
  • The safety of your home

Food Quality

From a palatability perspective, you may or may not get a decent result, depending on how high the internal temperature of the ribs rises.

180 F is very close to the temperature that needs to be achieved to effectively convert gelatin into collagen and create the tender texture out of the tough ribs as any kind of reasonable rate. If the temperature inside the ribs doesn't rise that high--and air is a poor transmitter of heat, which is why you can stick your hand inside a 500 F oven--you may not get a great result.

Food Safety

The same issue--temperature--is key for safety.

You want the ribs above 140 F as quickly as reasonably possible to inhibit pathogen growth. It is not clear that the ribs will get that hot in such a low oven, or if they do so, if they will do it in a reasonable period of time (less than say, an hour) so you may have a potential food safety issue.

This is exacerbated by the fact that most ovens have a considerable margin of error between the set temperature and the actual temperature (which also varies above and below the set point).

Home Safety

RI Swamp Yankee has located a reference to the US Fire Administration which clearly recommends not leaving cooking appliances unattended when no one is home:

The leading cause of fires in the kitchen is unattended cooking.

  • Stay in the kitchen when you are frying, grilling, or broiling food. If you leave the kitchen for even a short period of time, turn off the stove.
  • If you are simmering, baking, roasting, or boiling food, check it regularly, remain in the home while food is cooking, and use a timer to remind you that you're cooking.
  • Stay alert! To prevent cooking fires, you have to be alert. You won't be if you are sleepy, have been drinking alcohol, or have taken medicine that makes you drowsy.
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Millions of people have been leaving gas and electric ovens on unattended for many decades without incident. I am unaware of a single instance of a fire being caused by an oven that was in proper working order and being used properly. As @Joe pointed out, there is insufficient oxygen in a closed oven to support much of a fire at all. Any oven fire, even a grease-fed fire, can be extinguished by simply not opening the door. Even if a fire did somehow manage to sustain itself, it's in a sealed metal box and has nowhere to go. –  Carey Gregory Sep 30 '13 at 15:04
    
@CareyGregory I would like to believe that. But I am not recommending it in this litigious society. If there is a credible document from a fire department saying the practice is okay, I would love to reference it and change the advise. The risk, after all, is not from properly functioning or well cared for ovens, but from those that are not. Gas ovens also necessarily have an ongoing oxygen source. –  SAJ14SAJ Sep 30 '13 at 15:09
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180f ifor 9 hours is easy hot enough to reduce the gelatin down. Many recipes suggest similar timings and temps, there is no health risk –  NimChimpsky Sep 30 '13 at 15:28
    
@NimChimpsky If the internal temperature of the ribs is in fact 180 F, yes. That is not likely in most ovens set to 180. –  SAJ14SAJ Sep 30 '13 at 15:29
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@SAJ14SAJ - The UL seal (in the US) on the oven is the certification you're looking for. Ovens are designed to be left on for hours at a time. Yes, a gas oven necessarily has an oxygen source at the bottom of the oven in the burner area. Again, that area is a sealed metal box intended to contain fire. I spent 15 years in the fire department and have seen precisely zero oven fires that went anywhere at all unless the door was opened. And even then the most damage I've ever seen is some smoke. –  Carey Gregory Sep 30 '13 at 15:59
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Slow cookers are generally recognized to be safe when used unattended - and there are a variety of slow-cooker rib recipes out there. I've made them to great success before - they're fine braising in their own juices , or with a little liquid, such as root beer or Dr. Pepper.

The problem with the oven is the lack of temperature control at low temperatures and the amount of electricity it uses - with a gas oven, carbon monoxide would be a worry leaving it on for 8 or 9 hours at a stretch, as well as steep gas bills. There would be a very low risk of fire, but enough of one where fire safety experts do not recommend leaving it unattended.

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