Is it safe to leave the oven on while unattended?
September 3, 2015 2:45 PM   Subscribe

My husband believes it is safe to leave the house with the (electric) oven on. Maybe not 100% safe, but no less safe than leaving the house with any electrical appliances plugged in. I am not so sure, and I am failing to find any reliable information online. Please resolve this disagreement: how unsafe is it to leave the house with the oven going?

I would really appreciate any facts or figures. Google searches are filled with Q&A forums where people are more than happy to state their opinion on the matter... But very little of it seems to be at all informed. That's not going to help me! Both my anxiety and my husband's lack of anxiety are completely uninformed. So, I'm hoping AskMe can give me what we need to draw an informed conclusion on the matter.

We have an electric oven with only a top heating element. If we left it unattended, it would be at a low temperature, usually slow-cooking some meat.
posted by meese to Home & Garden (20 answers total) 1 user marked this as a favorite
Mod note: A few comments deleted. Folks, OP's looking for facts, stats, outside sources etc. Let's stick to those please.
posted by LobsterMitten (staff) at 2:57 PM on September 3, 2015

Here are three sources, all of which basically agree that you should not leave a cooking source unattended as it is a leading cause of house fires:

How to prevent cooking fires and related injuries "Cooking is the leading cause of house fires..." and "Always stay in the kitchen when cooking."

•Unattended cooking was by far the leading contributing factor in these fires.

Unattended Stoves

Another cause of residential fires is cooking, but not due to defective stoves or ovens. Often, it is because of unattended pots or the burner being left on accidentally -and who hasn’t done that at least once or twice?

posted by Michele in California at 3:00 PM on September 3, 2015 [4 favorites]

Cooking fires are a real thing. The stovetop is more dangerous than the oven, but oven fires happen. If you're there, then you can turn off the oven, grab the extinguisher and call 911.

Based on 2007-2011 annual averages:
- Unattended cooking was by far the leading contributing factor in these fires.
- Two-thirds (67%) of home cooking fires started with the ignition of food or other cooking materials.
- Ranges accounted for the largest share (57%) of home cooking fire incidents. Ovens accounted for 16%.

posted by 26.2 at 3:01 PM on September 3, 2015 [6 favorites]

I was going to link the same site, but I'll add that if you're slow-cooking meat, you'd want the temp to be lower than 200 degrees, which is around where beef fat will smoke, and so that'd be relatively safe... but will your oven maintain a temp that low?

Personally, I slow-cook meat with an immersion cooker, and I'm ok leaving that running for a few days...
posted by Huck500 at 3:13 PM on September 3, 2015 [1 favorite]

If you follow the links on 26.2's link, the percentages are based on 156,600 cooking involved fires over a 5 year period.

Taking the average, you're looking at 31,320 cooking involved fires every year, ~5011 of which are due to ovens.

Wikipedia says that there are 117,538,000 households in the US. Which I think means (and this is where my poor statistical training may lead me astray) is a 0.0043% chance of any given household having an oven fire in a year.

Using a different data set:this Guardian article seems to say that dishwashers are responsible for more fires in Britain than ovens. And I think it's safe to assume that there are more ovens in Britain than dishwashers. Do you leave the house with the dishwasher running?

My unwanted opinion: It's safe enough but don't be dumb (don't leave flammable papers/cloth on or near the oven while it's on, don't put paper in the oven, etc, don't do the weird NYC thing of using the oven as storage so stuff catches fire when you preheat without looking first).
posted by sparklemotion at 3:23 PM on September 3, 2015 [11 favorites]

I was going to add that you are kind of both right. I have gone through periods where I would start dinner by sticking something in the oven and then taking my pregnant self and my toddler to the playground for an hour. I have also gone through periods where I was baking a lot of greasy stuff and not cleaning the oven frequently enough, thus I had the puddle of grease in the oven catch fire more than once as my clue that I really needed to clean the oven. I stopped cooking greasy foods and stopped having oven fires.

So I would say that if the oven is clean and the item being cooked isn't the sort to leave a puddle of grease in the oven and you take other precautions, this is not some crazy high risk. On the other hand, the safest thing to do is make sure to always be there when it is on. I think there are two things to consider: cost/benefit ratio in terms of your lifestyle and personal risk tolerance. I am innately risk averse. My preferred answer is "Never leave it unattended." Nonetheless, while pregnant and raising a two year old, for a few months, starting dinner and leaving for the playground made sense to me and helped make my harried life work.
posted by Michele in California at 3:36 PM on September 3, 2015 [2 favorites]

I had an electric range and the circuitry went bananas one day, I came home to find all my burners had flipped on and I couldn't shut them off. I had to pull out all the heating elements and get a new stove.

I have no idea how often this happens but it certainly happened to me.
posted by kinetic at 3:41 PM on September 3, 2015 [1 favorite]

A different report from FEMA: On average, an estimated 164,500 cooking fires are reported annually in residential buildings in the United States with 94% of those being confined fires. (I'll theorize that the fact that people are often near the stove/fryer/grill probably contributes high rate of confined fire. You're there and you put it out or remove the heat source.)
Careless cooking activities are typically responsible for cooking fires. When a factor was noted as contributing to the ignition of the fire, unattended equipment, such as people leaving food on the stove or in the oven and forgetting about it, accounted for 43 percent of nonconfined residential cooking fires. Unattended equipment was, by far,the leading specific factor contributing to ignition and was nearly four times greater than the second leading specific factor, heat source too close to combustibles (12 percent) (p.7)
It really depends on what you're asking. If you're asking if there is a higher risk of fire with unattended cooking, then yes there is. If you are asking if there is an acceptable risk of fire with unattended cooking, then that is your call.
posted by 26.2 at 3:52 PM on September 3, 2015 [8 favorites]

> Wikipedia says that there are 117,538,000 households in the US. Which I think means (and this is where my poor statistical training may lead me astray) is a 0.0043% chance of any given household having an oven fire in a year

You don't know how many of those fires were caused by ovens being left unattended.
posted by The corpse in the library at 5:03 PM on September 3, 2015

Statistics aside, I have had a real experience with this with an electric stove. The heating element in the oven ruptured while in use, causing a fire. Emptying an entire ABC fire extinguisher did not put out the fire. The fire only went out when the power was cut to the entire home. If we hadn't been home at the time, the entire house could have gone up in flames.
posted by LilithSilver at 6:40 PM on September 3, 2015 [6 favorites]

You don't know how many of those fires were caused by ovens being left unattended

True, but I'm not sure that's important. Fires are likely to happen when they happen, not because they're left unattended. But if you're home and the room starts filling with smoke, you can turn off the oven and use a fire extinguisher or throw salt on the flames or whatever you do, and you may never report that fire. So it wouldn't show up in statistics. If you're not home, and can't interrupt the process in that way, it may be far more likely to become a "fire" as in the fire department is called and there is perhaps an insurance claim.
posted by Miko at 7:33 PM on September 3, 2015 [1 favorite]

I sometimes assess risk by thinking about what would happen if the worst-case-scenario event, no matter how unlikely, came to pass. In this case, that would involve a potentially large fire burning out of control in your home with nobody to witness or stop it until significant damage had occurred.

I then think about what inconveniences I would need to bear to eliminate this risk. In your case, the inconvenience is being in the house while you cook things. In the context of my lifestyle, that would be a small inconvenience to manage relative to the catastrophe of a house fire.

So, if the inconvenience is small, and the stakes high, why risk it?
posted by delight at 10:35 PM on September 3, 2015 [4 favorites]

I have no statistics to link, and this can get blammed if it's unwanted... But when my parents managed a large apartment complex, we had several older stoves short out and fail in weird possibly fire hazard ways within a few years... And several of the replacement, brand new, basic stoves. The house I lived almost immediately after that had a serious gigantic arc freak heating element failure. Which wasn't the first one I had seen.

Usually you just cut power and swap the element, or junk the stove if the electronics/hv circuitry screwed up... But yea, the element can fail in a way that makes an insanely hot arc. I wish I had a photo of the damage I've seen it do to the interior of the oven. It can straight up melt metal.

Have I turned on the oven and gone to the store? Yea. Would I recommend it? No, I do lots of stupid shit. I'm not a role model.
posted by emptythought at 11:42 PM on September 3, 2015 [2 favorites]

I'd rephrase the question: what would be the most dangerous thing to leave turned on while you are not at home?
posted by gorcha at 1:08 AM on September 4, 2015 [3 favorites]

I think part of the problem with trying to get statistics for this, is that all of the small contained fires that people stopped because they were home, will go unreported. Which means all of the kitchen fire stats are either from unattended fires or fires that went out of control too quickly to be contained.

Just last week I had to put my toaster oven out because it caught. I really need to clean that thing.
posted by mayonnaises at 5:20 AM on September 4, 2015 [2 favorites]

I suspect toaster ovens are actually more dangerous. They get really hot and are less insulated from things around them, and the crap that accumulates on their heating elements seems to burn more readily. I have been present at several toaster-oven fires in my life, but never oven fires. Still, I wouldn't roam far with the oven on. Once I left it on doing a low-and-slow roast while I got someone at the train, but it makes me nervous.
posted by Miko at 6:03 AM on September 4, 2015

The issue isn't the oven itself -- you can leave a clean, empty oven on for weeks without harm, other than to your energy bill. It's designed to be hot.

The issue is what's *in* the oven. While it is cooking, it's below ignition temperature, and not burning. But should it overcook and burn, well, then it can reach ignition temperature, and the oven will keep pumping heat into it. That's what ovens are built to do, after at. At some point, that will catch fire and get *much* hotter, and if that fire exceeds the temperature that the oven is designed to contain, then you are in trouble.

If you are there, the smoke coming from the burning food will warn you well before the food reaches the "turn into a flaming mass which ignites the oven" stage, but if you aren't, you don't smell that and that's the situation that results in you coming back to no home.

Similar class: clothes dryer fires, where someone loads up a dryer and leaves. I almost lost my place because the people in the apartment below me did that and I almost left. If I hadn't been lazy about going to the store, I wouldn't have been here either. I was, smelled something odd, noticed smoke coming out of a latch hole, went downstairs, saw window blinds melting, and called the fire department. Then I grabbed my car keys, wallet, backup hard drive, and fully expected to have to buy everything else new. Nope, CFD put it out -- but we were about 10 minutes away from a fully involved structure fire.

And that was the difference -- ten minutes.

I think part of the problem with trying to get statistics for this, is that all of the small contained fires that people stopped because they were home, will go unreported.

BING BING BING. mayonnaises hits that one on the head. It's not the ones that almost caught that get onto the stats. It's the one that get called in. So the reported data has a big selection bias. Lab testing really shows us the potential fire issue with leaving food cooking unattended. The most risky is food with high fat or oil content.

The exception is crockpots/slow cookers explicitly designed for very long and slow countertop cooking which keep the temps below 250F/120C and have fusible links and thermostats in them to disconnect themselves from power should they go much above that. You can leave if that's what you're cooking with. Setting fire to anything with those is quite the challenge.
posted by eriko at 6:08 AM on September 4, 2015 [8 favorites]

Yeah, selection bias is what I was going for here as well. It's difficult to reason from incidence statistics.
posted by Miko at 6:22 AM on September 4, 2015

I don't believe you need statistics if you listen to even one horror story from someone who has done this and loses their pets/possessions/house. You MUST at least be in the house if you're cooking, so you can hear and respond to the smoke alarm if it goes off. And preferably you should periodically peek into the kitchen to make sure everything's alright, because smoke alarms fail too.

I was in the habit of leaving bone stock to simmer at a low temp on the stovetop overnight while I slept. In one old rental house in Seattle, we had a wonky (electric like yours) burner that would suddenly go all the way to high for no discernable reason. I stopped using it when we identified that problem, but apparently it affected another burner as well, which I didn't know about until I woke up early one morning to use the bathroom, only to discover the house was full of smoke and the stock pot was dried up and the bones were blackened and burning.

We had a dog. It was already really smoky, and had I not woken up when I did, she would likely have died from smoke inhalation. The kitchen was separated from our sleeping area by two doors, and the smoke hadn't reached us yet but had totally saturated the living room (where the dog slept) and kitchen.

We had disabled the smoke alarm because it went off too easily, during the normal course of cooking.

I don't want you to find out the hard way, like I did, that electrical appliances malfunction and that there can be dire consequences from assuming it won't.

Do not leave your oven on when no one's home. Just don't.
posted by mysterious_stranger at 5:34 PM on September 4, 2015 [1 favorite]

You might also want to consider the likelihood of something happening to keep you out of the house for longer than intended, which could be problematic irrespective of how safe the oven is. I haven't done well at finding useful statistics, sorry, but - your car could break down (here's a Telegraph article claiming that one car in three breaks down each year), an accident could close the road, you might lose your house keys or have your bag stolen (another Telegraph article - I guess they like this sort of thing - claims there were more than half a million instances of bag theft or pickpocketing in the UK in 2010, a little under one theft per hundred of the population), you could have an accident yourself and wind up in hospital, and so on.
posted by ManyLeggedCreature at 8:05 AM on September 5, 2015 [2 favorites]

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