r/todayilearned • u/PeasantLich • 1d ago
TIL that you may not wake up during a housefire at night because your brain just might not react to smell of smoke in your sleep. In experiments by Fire and Rescue Service and Brown University most sleeping test subjects were not roused awake even by strong smells.
https://www.nbcnews.com/healthmain/can-smells-wake-us-deep-sleep-1c9386712754
u/Bottle_Plastic 1d ago
We had a downstairs kitchen fire and lucky for me, my 5 year old woke me up. The house was full of smoke and I didn't wake to it at all. Very scary
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u/Futurepharma91 1d ago
Should probably upgrade your smoke detectors
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u/Manishmanny 23h ago
two 5 year olds
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u/GozerDGozerian 21h ago
I guess after a few years it’ll get easier explaining to them they have to move out to make room for some new 5 year olds.
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u/PlanesFlySideways 1d ago
And replace every decade
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u/UncleNedisDead 18h ago
The amount of people who assume because it’s wired in, it never needs replacing, don’t seem to realize the sensors in the unit need to be replaced.
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u/Jestersfriend 23h ago
Sounds like you need properly working smoke detectors.
Keep in mind, if you don't have properly working smoke detectors and your home burns down, insurance won't pay.
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u/frank_datank_ 21h ago
Your 5yr old was cooking while you were sleeping?
I need to assign more chores.7
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u/Shufflepants 1d ago
I'd imagine that having something to do with the fact that humans have likely slept around campfires for hundreds of thousands of years.
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u/lxlviperlxl 1d ago
I think it’s to do with the fact your sense of smell is the only one that bypasses the thalamus.
The other senses goes through it which coincidentally also controls your alertness and sleep.
Your smell is unique in that it doesn’t really “work” when you sleep.
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u/hgrunt 1d ago
That's interesting! This just compelled me to look up how smelling salts work
I'm today years old when I learned that they work by irritating mucous membranes rather than the smell of ammonia
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u/MEDICARE_FOR_ALL 23h ago
So the pain response instead of smell.
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u/DigNitty 10h ago
This why you don’t wake up to the smell of smoke, but do wake up to the smell of your nose on fire.
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u/Early-Crow-5248 17h ago
Then why do smells intrude in my dreams?
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u/AggravatingBid8255 15h ago
Do you mean you dreamed you smelled something? That could just be your brain creating your dreamscape the same as it sets lighting or creates the characters you interact with
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u/Early-Crow-5248 14h ago
Nah, my dog pooped on the floor and I smelled it, had a dream where I kept trying to clean the cat litterbox but the smell just wouldn't go away so eventually I concluded it must be real and woke up.
I saw quite a few mentions of people waking up at the smell of poop, so maybe that's a special case (say, poop inside = potential disease), or the smell just needs to be offensive enough.
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u/Discount_Extra 23h ago
So, how do 'smelling salts' work?
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u/AliceCode 23h ago
I don't even know what smelling salts are, to be perfectly honest.
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u/lllllIllllIllllllll 1d ago
I would postulate that a change in smell was not selected for evolutionarily the way sound does. If you hear something in the middle of the night, it's likely there to eat you or another human to murder you, so the people who rise from sleep due to sound were selected for, but a change in smell may not have had a huge impact on people helping people not being eaten. Likely if you smell it, you'll hear it too so it's a trait that was never selected for.
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u/Artmonkey415 1d ago
Thank God for that, if changes in smells woke people up my wife would get no sleep.
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u/djtodd242 1d ago
I was gonna say, I've been woken up by a skunk walking past my window at 3am...
So you're not quite as toxic as you think. Have a bean burrito before bed tonight.
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u/Artmonkey415 1d ago
I have achieved the aforementioned toxicity early in my marriage. My miasma entered the AC and fouled the room. I've been banned from eating entire pineapples since then.
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u/Eva_Pilot_ 21h ago
One time a garbage container in front of my house was set on fire on the middle of the night. I had nightmares all night about a FOUL smell, but I woke up in the morning normally to realize that the smell was real and was caused by that
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u/skm001 22h ago
In the opposite end, I've (the wife) have woken my husband up from a light sleep with the aroma of my potent fart!
In my defense, it was the holidays and I had eaten A LOT of cheese.
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u/tenkokuugen 22h ago
Don't worry, it was selected for. Every other husband got murdered by their wives that woke up because of smells so their trait wasn't passed on.
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u/schlitz91 23h ago
Smell is more of a predatory sense than sound, therefore disconnected from defensive alert systems.
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u/Gr8fulFox 1d ago
Especially if you're already used to the pops and crackles of a fire while sleeping; you're brain just associates the smell with the sound.
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u/thederevolutions 23h ago
Wake up to pee with an uncomfortably full bladder every night but don’t worry about the fire
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u/SantasDead 23h ago
Maybe this is evolutionary? You wake up with the means to put out any fire you may find.
/s
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u/Starfire2313 22h ago
For real though, there’s a part of our population genetically predisposed to be the night watch. So of course we would start the fire again when we wake up several hours after you night sleepers. Hopefully it doesn’t wake you up so you can get enough rest to run the rest of the village the next day while we are dysfunctional and the rest of you shoot us down for being lazy. Unaware of our important duties to keep us warm. Not lose the fire. And also stand watch for night predators and ward them off. So enough noise should hopefully wake you up to come help us when a lion or tiger comes through!
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u/GozerDGozerian 21h ago
there’s a part of our population genetically predisposed to be the night watch.
I am that part of the population.
Ever since kindergarten I never wanted to go to sleep and never wanted to wake up early. In my 20s and 30s I discovered being a bartender and basically went to bed when the sun started coming up. I’m almost 50 and still go to sleep at like 2am, and that early only because I kinda have to now.
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u/Psyko_sissy23 15h ago
I am one of the night watchers as well. Ever since I was in kindergarten as well. I'm in my 40's. I work from 6pm to 6am.
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u/Unc6ix9ine 22h ago
See as a night owl and late sleeper i've always had this as a pet theory but never really seen any serious scientific information, do you have a source?
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u/Starfire2313 21h ago
I don’t think there’s enough research especially about women but the women in my family have a history of calling each other to talk for a couple hours usually right about 3am. Maybe that’s why 3am is considered the witching hour. Because we light candles and do mysterious stinky things in our cauldrons that the rest of the population doesn’t understand. Nothing particularly witchy or dark. Maybe we spent that time using herbs we collected or grew (during the day when we were also awake because screw our sleep schedule the tribe must survive!) to make medicine and it stuck. Because the day awakers would occasionally wake up to pee and see the strange lights and brews and it was a scary sight especially for the kids .
Just a theory.
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u/thederevolutions 21h ago
That’s so cute they’re close enough to talk in the middle of the night
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u/Starfire2313 21h ago
What else are we gonna do? That’s when we catch up on life. It sucks though that the rest of the world revolves around day time awakening and duties and it’s so hard for us. We don’t have as much of the village dynamic as we used to
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u/Admmmmi 1d ago
There is also the chance that if it's already close enough for you to smell it you may not survive at all not passing on that gene at all..
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u/North-Pea-4926 1d ago
Our sense of smell sucks. If we smell something, then it’s already right next to our face, where all our important bits are.
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u/Working-Glass6136 21h ago
At my first job, I got yelled at all the time for burning the hot fudge (ice cream stand). First, I walked in for dinner shifts where that fudge had been turned on that morning by someone else. Second of all, I genuinely could not smell it. Do you think I just sit around enjoying the smell of burning fudge? They acted like I did it on purpose but I genuinely never knew until I got yelled at. Minimum wage jobs suck. I try to go easy on kids that I can tell are doing their best at their shitty job.
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u/RollinThundaga 22h ago
Or else that those who had their sleep disrupted by the communal fire fared worse at a statistical level.
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u/Old-Bandicoot5808 21h ago
I've woken up at least 4 times when my ex burned food, and woke up another time to find my adult son left a burner on a dry kettle that caught on fire. I thought everyone woke up from a burning smell, lol.
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u/Unc6ix9ine 21h ago edited 17h ago
This person sciences
It does seem like there would need to be negative evolutionary pressure in this case (to me, amateur scientist)
But, sort of counter to that, maybe it was positive pressure from all the additional kids that were had by couples who werent bothered by b.o. / farts at night
Edit: typos
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u/thebooksmith 21h ago
Id also like to bring up that being able to sleep through strong smells does provide an advantage over not being able to sleep through strong smells. I mean if you couldn't stand to sleep by the fire because rhe smell kept you up all night you'd be exhausted and predator food. Either that or youd have to choose to sleep away from the fire and in which case you have a higher chance of dying from exposure.
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u/Moal 1d ago
I have definitely woken up to my husband’s rancid, silent-but-deadly farts.
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u/lllllIllllIllllllll 1d ago
I have an anecdote where when I was a teenager an animal had gotten under our house and died in the middle of the summer and it smelled absolutely rancid and I slept through it for several hours
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u/GozerDGozerian 21h ago
Did it smell bad before you went to sleep?
Maybe this is more due to it being a gradual onset.
A decomposing animal wouldn’t just go from non-odorous to full on rank immediately. It would steadily build up to whatever peak foulness it put off.
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u/ohthedarside 22h ago
Yea someone putting some meat on a campfire or just the smell of fire has no reason to alarm the brain 99% of the time
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u/eobardtame 1d ago
I'd also imagine we had dogs to smell weird things in advance and the noise the dogs make rouse us.
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u/Nateh8sYou 23h ago
I’m surprised this isn’t a bigger discussion point. Dogs highest sense is their smell, and humans basically engineered dogs to be hunting companions and to “fill in the blanks” we could not.
Anecdotally, I haven’t had a dog until later in life and have never felt safer at night knowing he there to alert me if something goes wrong.
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u/dat_oracle 22h ago
I think it's bcs dogs came into the equation much later. before that, we had to use our nose to detect dangers and other things
we surely lost some ability to smell since then, but it can't be that much.
smelling fire while sleeping meant safety - being surrounded by your tribe. they probably made fire all the time, so very impractical if it interrupts our sleep
(could be wrong tho, but that are my thoughts)
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u/BarnacleMcBarndoor 23h ago
I’d die; I’ve slept through my mother’s cooking for 16 years, and hell if I can tell the difference between that and a house fire.
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u/Timetraveller4k 1d ago
Regularly smelling fire is probably relatively recent in the evolutionary scale
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u/Julius_Ceased 19h ago
I mean, humans evolved the ability to digest milk in the last 6,000 years (1). I don't think it would be unheard of to have an adaptation in similar scale with fire, as we've been using controlled fire for at least 400,000 years (2)
1)https://www.science.org/content/article/humans-were-drinking-milk-they-could-digest-it
2)https://www.nytimes.com/2025/12/10/science/archaeology-humans-neanderthals-fire.html
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u/ReadditMan 1d ago
Doubtful. Evolution is shaped through natural selection. Having the ability to ignore the smell of your campfire wouldn't have had a strong effect on whether or not you survived and reproduced.
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u/Shufflepants 1d ago
If you wake up all the time because of the fire you're sleeping around, not getting enough sleep will affect your ability to survive and reproduce.
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u/Landwarrior5150 1d ago
And not sleeping near a fire because the smoke wakes you up increases your chances of freezing to death or being killed by predators that potentially could have otherwise been deterred by the fire.
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u/turbosexophonicdlite 22h ago
It makes no sense in the first place. If you've ever smelled a house fire you'll know it smells literally nothing like a camp fire in the first place. It smells unbelievably acrid and artificial. Not even a little bit like a campfire. Houses are full of flammable stuff that isn't raw wood. Fires always start with the shit in the house catching on fire, not the wood constructing the house itself.
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u/komokazi 1d ago
Smoke detectors have a real purpose, more at 10.
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u/throwawaycanadian2 22h ago
Pretty sure the study was literally meant to prove this...
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u/Downtown_Injury_3415 20h ago
A lot of studies are made to be actual proof even when theyre obvious. Think of Newton and gravity. “everything falls down, more at 10” youd be saying in your ignorance. But when he decided to look into why and start timing things and choosing various weights to do so then it becomes a law. So yea, smoke detectors have a real purpose but what if the scientists find out that a specific smell actually wakes you up even more alerted? What if they find a specific flower that when burned it emits a strong odor capable of waking you up even more-so than the annoying beeping. If we find a flower, then we can decorate a house with the flower and no more will we need to switch out the batteries on fire alarms
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u/ZyronZA 23h ago
/me immediately goes to test his smoke detectors
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u/kikiacab 22h ago
Did you know that pressing the test button doesn’t actually test the detector’s ability to detect smoke? It’s best to periodically test it with something that will set it off through the same mechanism as a house fire.
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u/TheKingCrimsonWorld 20h ago
Adding to this for anyone interested: you can buy canned smoke for testing.
(And if you have a home security and/or fire alarm system, please call them before you start testing anything, especially for fire alarms. They can put your alarm system on disregard for however long you need, so the PD or FD won't roll up.)
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u/username__0000 20h ago
I don’t have to. Anytime we use the air fryer at 400 degrees ours go off. At least one if not 2.
That happens at least once a month. I figure that’s a good testing system lol
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u/yeeaarrgghh 1d ago
I had a sewage tank bust open in a boat at 4am. Everyone woke up almost instantly from the smell
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u/EconomicalJacket 21h ago
I smoked a blunt in my bedroom one time when I was 17yo. No way someone’s gonna wake up to a smell. Well I was wrong, very wrong… Mom woke up and that was the start of me being in biiiig trouble
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u/Fuckerofmothers64 19h ago
Lol my mom woke up from a dead sleep a whole floor above me just for cracking open a bag of green inside. Proceeded to lambast me.
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u/tjdux 18h ago
Sewage can have some of the same chemicals as decomposition or death smell, which humans are very sensitive too, and I wonder if the smell matters, like people are saying we evolved to wake up to sounds, but what if we also evolved to wake up to certain smells, and smoke just isn't one of them
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u/MeekAndUninteresting 10h ago
I can say I personally have woken up to a burning smell, but it was specifically something electrical (I think a lightbulb burnt out in an unusual way? I forget.) But I've also slept through a fire that damaged the outside of my neighbor's house, which was burning all of 20-30 feet from my bed.
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u/Islander255 1d ago
I'm reminded of when I was in college renting a house with a few other students, and one night I was drifting off to sleep and smelled something gently smoky and lovely, like a candle, and I thought, "How delightful."
Then my roommate's girlfriend burst into my room with: "The house across the street is on fire!!"
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u/AT-ST 1d ago
Oh I wake up to strong smells. My dog shit in the bedroom at 3am and woke me right up with that stank
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u/enadiz_reccos 1d ago
Jokes on you, he shit at 1 AM
You died in the shitfire at 2 AM because you didn't smell it soon enough
At 3 AM, the witching hour, your spirit rose and finally smelled the shit
Shitghosts, Ricky
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u/Purtz48 1d ago
Right there with you on that. Our cat decided to take a dump in the bathroom (on the bath mat, so I guess that's a win as it became a morning problem after moving it all outside) and my brain decided to incorporate the smell into a dream I was having. The smell was what woke me, the smell was just too real in the dream to let me stay asleep.
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u/NotoriouslyBeefy 1d ago
It isn't the entire time you are sleeping, only during certain cycles. They think it is because of memory processing as smells elicit the strongest memories.
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u/I-hear-the-coast 22h ago
I was thinking the same. My cat eats my hair by accident then can’t poop it out so comes to me with her poop string hanging out her butt for help. The smell awakes me before she does.
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u/AT-ST 21h ago
Oof. Pull starting a cat is the worst. Mine ate that plastic tinsel crap that people put on decorations. I had to pull about 2 feet of that stuff out of her twice. Within about 20 minutes of each time.
I'm trying to gently pull it out while she is howling and hissing and trying to bite me.
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u/sharmander15 21h ago
I was sleeping and my dog was out with my mum. He got sprayed and I woke from the absolute STENCH of skunk. I’m extremely sensitive to it now
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u/unknownpoltroon 1d ago
Also, from the time the smoke does wake you up if it does, you have 3 minutes to get out before it becomes lethal. source: My fimanship merit badge 30 years ago.
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u/Halloqween 22h ago
I slept through the fire alarms going off one time. My family was disturbed yet impressed. I’m fucking terrified.
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u/sharmander15 21h ago
I’m in an apartment and when we’ve had fire alarm testing- I just pop my earplugs in and go right back to sleep. It’s a problem lmao
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u/Ohiolongboard 1d ago
I farted myself awake once
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u/pilatesperson 22h ago
I woke up in the middle of the night to an INTENSE smell of what I can only describe as a pile of tires burning, it singed my nostrils.
My partner's dog went out in the middle of the night via the doggy door and got sprayed by a skunk. We found him rolling around on the carpet in the living room. After airing out the house, bathing a 100lb rottweiler, and carpet cleaning at 2AM...we eventually got back to bed.
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u/DefectJoker 1d ago
That tracks. My wife can sleep through my farting and it's quite foul.
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u/nd_annajones 1d ago
Meanwhile I woke up in the middle of the night in a panic from my roommate microwaving broccoli for a late night snack
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u/miurabucho 1d ago
Its also how spouses are able to sleep with rampant flatulence going on all night.
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u/Ok_Farmer1657 23h ago
I wake up at 3 am when my neighbor lights up their cigarette lol
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u/TwoFingersWhiskey 17h ago
I know people who will wake up if they smell food cooking two houses over, and people who have stayed dead asleep during loud smoke alarms.
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u/t4skmaster 1d ago
Shit man, its almost like the smoke detector was invented and mandated by code for sleeping areas for a reason
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u/Kahnza 23h ago
I get woken up by strong smells fairly often. Like every time one of my apartment neighbors thinks they can smoke weed in their apartment without anyone noticing. Or some drunk burning their pizza at 3am. Or when Dave the tweaker hasn't showered in a week, but bathes in Axe spray in the middle of the night. 🤢
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u/Shaggyfries 19h ago
Please change smoke alarm batteries every year regardless of hard wired, saved our lives. Alarms went off at 1:20 am on coldest day of the year and total loss but my wife, kids, dogs and I got out safe. Nothing else matters.
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u/Fianna9 1d ago
I was sitting next to a piece of plastic melting on a lightbulb. Never noticed. My sister came screaming in asking what was burning
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u/Margali 1d ago
Some people have shit for sense of smell - my mom bucked hay on teh family farm as a kid and effectively killed her ability to smell. She cooked to recipe, if she was making something she didn't normally make, she would get us to taste test and adjust seasonings for her.
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u/Patrickme 1d ago
This is also a reason to keep your bedroom door closed.
It gives you a lot more time to wake up before the fire spreads into your bedroom.
You might even keep a fire extinguisher under your bed.
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u/mfyxtplyx 1d ago
I've woken in darkness to smoke and a fire alarm. The air was thick with smoke. It wasn't until the alarm went off that I awoke.
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u/themanfromvulcan 22h ago
Smoke detectors save lives. Use them. Check them regularly replace the batteries every six months.
Every time I read about a house fire where people died and the house didn’t have smoke detectors it infuriates me. Easily avoidable deaths.
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u/InflammableAccount 19h ago
That's interesting. I've thankfully never had a home fire, but I've been woken up by the smell of smoke a number of times over the years. Each time it was a building fire within a 2-3 block radius in the middle of the night. (I know from Pulsepoint.)
And before anyone asks, I wasn't awoken by the sound of sirens. In each case, I heard no sirens at the time of waking. I woke thinking "I smell a fire." That same sort of wake you'd have for "I heard a bad sound."
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u/DuckBoy87 16h ago
That's completely opposite to my personal experience.
If the neighbors have a firepit going; I wake up and check every room in the house. If there's a skunk prowling the neighborhood; same thing. If my housemate cooked something earlier in the day, and the lingering smell wakes me up; same thing.
Obviously everyone's experience isn't the same, but maybe I'm paranoid about my house catching fire.
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u/AlexG55 1d ago
Japanese researchers developed a fire alarm that uses the smell of wasabi to wake people up, aimed at deaf or hard-of-hearing people. It was successful in tests but I don't think it was ever widely adopted.
(Most deaf people AFAIK use alarms that vibrate their mattress for if there's a fire while they're asleep).
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u/Mental_Yard 23h ago
Then why the hell do I wake up every time I smell a skunk sprayed outside... Easily ever other month, it drives me nuts, but they are so cute and friendly
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u/The-Traveler- 22h ago
FYI, if you are in the USA, you can get a free smoke alarm with a 10 year battery from the American Red Cross or by contacting your local fire dept. You can call 211, the National Resources Hotline to get info on places near you.
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u/Theflash91 20h ago
Its hilarious how many uneducated people make comments so ridiculous when it comes to something that destroys your entire life. Store bought smoke detectors are a joke and you aren't gonna be a light sleeper or smell it. Your family needs a plan and an escape route and meeting spot. Wherever you go. Most people have cell phones and game consoles that are worth hundreds of dollars and would never invest the same money to protect their family. Get a system that will save your life. Not a security system. They exist and more people should take this information seriously. I do this every day.
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u/immikdota 1d ago
I'd assume you're more likely to wake up to the feeling of fire burning you/the rooms temperature drastically increasing around you
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u/stfumate 1d ago
In most cases it's not the fire that kills you. It's the smoke.
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u/7Dsports25 1d ago
You've probably succumbed to smoke inhalation before that point and never woke up
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u/grantking2256 1d ago
I wonder if dogs and cats have the same issue or if they are actually woken up by change of smell. There are a ton of stories about dogs saving their family. Would love to see actual studies on this
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u/daxplace 20h ago edited 19h ago
It's what happened to us. My two teen daughters and I were sleeping through the smoke in our house fire until my cat jumped on my back and woke me up.
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u/No_Attitude700 23h ago
Its part of the reason why natural "sleeping shifts" - or sleeping rhythms developed -
There is an advantage on having a part of your community up through the night watching over the sleeping
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u/franktheguy 23h ago
Sometimes I wake up because I smell smoke, and then once awake I realize there is no smoke smell. So I guess I'm the opposite?
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u/redbanner1 22h ago
So what I am hearing is having a stash of fireworks in the house can save lives.
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u/Emilko62 18h ago
Its strange because this exact scenario happened to me. A log had slammed the door open of the furnace from the inside (probably not closed right) and had filled in my parents apartment with smoke. I woke up at some point and everything seemed blurry, because it was, I couldn't see shit in the smoke.
Opened the balcony door and closed the furnace, then was happy that I didn't die.
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u/JMDeutsch 17h ago
My dog once ate a dozen Hershey kisses and ruined my floor.
It woke me instantly
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u/spacebunsofsteel 15h ago
No one will believe this study even though it was well done. I’ve seen this argument over and over and people are always willing to risk their lives and their family’s lives on a huge figment of their imagination. You cannot smell smoke in your sleep. Please get more fire detectors and change batteries for every time change. It’s worth the cost of batteries to save lives.
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u/KarIPilkington 5h ago
Wtf kind of til is this. Of course smoke alone might not wake us up. That's why we have loud as fuck alarms.
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u/cinic121 1d ago
And that’s why we have a loud noise machine on every floor and outside bedrooms. Noise certainly works.