Risk perception – of fans and fission reactors

Guest Post by Craig Schumacher. Craig has been commenting on nuclear power themed websites for about five years and has published his own blog, Channelling the Strong Force, since 2008. He formed the nuclear power advocacy organisation, Nucleus 92 Inc., in 2009. He is a regular commenter on this and other pro-nuclear sites under the nom de plume of Finrod.

Terror stalks the nation. Death; mysterious, invisible, and ineluctable to any who ignore the warning to flee from this killer haunts the suburbs and the villages, the apartment blocks and farmhouses, cowing folk high or humble, man, woman and child. All are fearful but the very young, so parents drill the message into children as soon as they are able to understand. No loving parent wants their child’s life cut short by misuse of this perilous technology.

Bar diagram for comparing risks. Length of bar is LLE. Asterisk designates average risk spread over total U.S. population; others refer to risks of those exposed or participating.

It was introduced recently, in historical terms. It was just one of a number of new technologies to arrive after the war when the great modernisation of all aspects of life began under the guidance of the government. No-one knew at first what a cuckoo had been put in the nest, what a deadly threat had been unknowingly foisted onto the people in this heedless rush into the future, but it emerged soon enough, and the terror began. Now the nation is fully aware of the danger. The trouble is the technology is just so darned useful that people won’t give it up, even though it holds such risk. Lets face it. Summers are hot, and who wants be without their electric fan? Not everyone has air-conditioning, and electric fans are cheap when you need to cool down.

I am referring, of course, to the well-known phenomenon of fan death. According to some, death will often ensue when an electric fan has been left running in a sealed room in which people are sleeping. This peculiar belief is widespread in the nation of South Korea, and nowhere else. The South Korean media occasionally runs stories about people who have been found dead in their bedrooms or apartments when an electric fan has been left running during hot weather. In any other nation in the world, those deaths would likely be listed as resulting from heat exhaustion, or indirectly from heat stress on an elderly person. In South Korea, however, no-one is in any doubt that insidious fan death has struck again.

In fact belief in fan death is so strong that the government has responded to community concerns by mandating that all electric fans sold in South Korea must come with a timer switch to cut the power after a few minutes should you be so reckless as to wish to go to sleep with the fan on, and people are encouraged to use it for their own good. Doctors, politicians and media figures solemnly warn people of the danger. The Korea Consumer Protection Board issues safety alerts granting the warnings official status. Doubtless, mothers drill the knowledge into the minds of the young, and another generation is indoctrinated into the gospel of fan death. And doubtless this virulent meme has resulted in many avoidable deaths in South Korea through the years, as elderly people die in the summer heat rather than risk fan death to keep themselves cool in the evening, or people succumb to diseases caught from insect bites following advice to sleep with their windows open rather than keeping such dangers outside and using their actually quite harmless fans.

Illustration 1: Electric fans ready for sale in South Korea. Note the cut-off timer switches.

No one seems to know how this idea got started, or why it started in South Korea and nowhere else, or why belief in it hasn’t spread beyond that nation. For some reason, this superstition has not managed to expand beyond the national borders, not even to the nutters of other countries. When asked how fan death actually works, the proponents offer a number of colourful accounts, such as the following, taken from Wikipedia:

The specifics behind belief in the myth of fan-death often offer several explanations for the precise mechanism by which the fan kills. However, as explained below, none of these beliefs stands up to logical or scientific scrutiny. Examples for possible justifications of belief in fan death are as follows:

– That an electric fan creates a vortex, which sucks the oxygen from the enclosed and sealed room and creates a partial vacuum inside. Indoor fans are not nearly powerful enough to change the air pressure by any significant amount. Additionally if the room is closed, the gases circulate only inside the room, not changing overall pressure with respect to the environment.

– That an electric fan chops up all the air particles in the air leaving none to breathe. This explanation violates mass conservation and well-known properties of molecules and gases, particularly that known breakdown energy of oxygen molecules lies in the ultraviolet range, far above the energy produced by a fan. Furthermore, atomic oxygen is highly reactive and would produce sharp-smelling ozone, if it was produced by some mechanism. It also ignores the nearly universal human tendency to wake up while being suffocated in a moment of sleep. Moreover, the theory makes no justifications for how and why a person will not suffocate while awake in a room which contains an operating fan.

– The fan uses up the oxygen in the room and creates fatal levels of carbon dioxide. An electric motor does not function by combustion; unlike a candle, the electric motor consumes energy supplied by the electricity, not from a fuel. The fan motor’s commutator does produce a small amount of ozone during normal operation; however, most AC powered fans use induction motors, whose brushless design eliminates any possible ozone production. Ozone can be fatal in high concentrations, but under normal conditions the gas would never build up to lethal levels.

– That if the fan is put directly in front of the face of the sleeping person, it will suck all the air away, preventing one from breathing. Bernoulli’s principle states that as air speed increases, air pressure decreases, meaning less air to breathe, but this effect would not be anywhere near dramatic enough to kill a person. Additionally, the resultant pressure gradient would yield flow from the high pressure surrounding area to the low pressure area, largely nullifying this effect.

– That fans contribute to hypothermia, or abnormally low body temperature. As the metabolism slows down at night, one becomes more sensitive to temperature, and thus supposedly more prone to hypothermia. If the fan is left on all night in a sealed and enclosed room, believers in fan death suppose that it will lower the temperature of the room to the point that it can cause hypothermia. Empirical measurements will show, however, that the temperature in the room does not fall, at least not due to the fan; if at all, it should rise slightly because of friction and the heat output of the fan motor, but even this is generally not significant. Fans actually make one cooler by increasing the convection around a person’s body so that heat flows from them to the air more easily, and by the latent heat of vaporization as perspiration evaporates from the body. However, there is no scientific study which indicates that this effect would be sufficient to cause hypothermia unless the temperature were already very low. Furthermore, discomfort will always wake a person long before they succumb to hypothermia.

– The fan overheats after it has been left on for too long, and ceases to cool the room, instead causing the already sweltering heat to increase uncontrollably until the person dies from it. The rational explanation is that during extreme heat waves, a number of people are going to succumb to it (older or sick people), and the existence of a running fan in the room they have died in is merely circumstantial.

– That a significant part of breathing occurs through the skin (false), and that the fast moving air from a fan makes “skin breathing” more difficult.

– That fans contribute to prolonged asphyxiation due to environmental oxygen displacement or carbon dioxide intoxication. In the process of human respiration, inhaled fresh air is exhaled with a lower concentration of oxygen gas (O2), and higher concentration of carbon dioxide gas (CO2), causing a gradual reduction of O2 and buildup of CO2 in a completely unventilated room. Other indoor sources of carbon dioxide include burning fossil fuels, such as a gas-fueled water heater, and seepage through foundations in areas of high CO2 soil content. Carbon dioxide is a colorless, odorless gas, and because it weighs 1.5 times more than normal air, it tends to concentrate toward the floor, depending on temperature and air currents. In South Korea, some people sleep on traditional floor mats, called yos, while others prefer western-style beds, and floor vents may be absent when ondol radiant underfloor heating is employed. According to The Straight Dope website run by the Chicago Reader newspaper, asphyxiation is an unlikely cause of fan death because “few rooms are totally sealed, and the fan would tend to keep CO2 and other gases well mixed.

So there you have it. None of the above ‘explanations’ are worth anything except possibly as research material for a study in psychology, but their existence seems to satisfy some need on the part of believers for a body of material to refer to, and besides that, “Everybody knows it’s true!“. This belief is now so entrenched in the South Korean national psyche that it would likely take generations of counter-propaganda to root it out. No-one has any inclination to undertake such a task, so they’re probably stuck with this idiotic meme.

Although we don’t really know how this belief arose, we can make some reasonable guesses about the process which must have occurred. South Korea was an impoverished, backward nation following World War Two, and was further impacted by the Korean War. Not until the mid 1950s could the government begin its massive development drive which resulted in the modern, wealthy, high-tech trading giant we see today. The people of South Korea went from pre-industrial stagnation to the forefront of the global economic system in the space of a generation. The sheer novelty of the experience must have been breathtaking. It’s little wonder that some of the new marvels were targets for misinterpretation.

The first news reports linking death to the use of an electric fan are from 1973, and was about a young person found dead in the same room as a running fan. It has been speculated that this and similar cases may actually have been drug or alcohol overdoses. There was likely a pre-existing myth about fan death for it to be considered a potential culprit. I suspect what probably happened was that a number of people had the experience of finding elderly relatives deceased due to heat stroke, with an electric fan switched on in the room, and distraught people searching for an explanation fixed their attention on the newfangled machine sitting there and still running in spite of the death of its owner.

This is a common human response to new technology. There are still people who remember the misgivings of elderly relatives about the introduction of electricity. One fairly common misunderstanding in the United States, for instance, was that a light socket should never be left bare and untenanted. There was a belief that the electricity could somehow leap out of the socket and cause all sorts of trouble, even if the switch was off. To ward off this danger, a blown bulb would be left in the socket until a new one could be found. Familiarity gradually eroded these beliefs, and perhaps in time to come, fan death will go the same way.

The fear of technology...

It’s only natural to be cautious about something new, and bundle what information you have into a grab-bag to establish a first-take danger zone around the thing in question, especially if what is either known or believed about it suggests problems. The trouble is, these preliminary responses are supposed to be just that, an initial assessment followed up with a more in-depth investigation to clarify the danger. They should not be taken for a map of uncharted territory forever off limits to understanding. The second step is the beginning of the journey into proper insight from which sound judgements can be made. It cannot be sidestepped without aborting that journey and rendering you helpless when assessing the potential danger.

Consider the matter of fan death. Due to a misattribution of cause and effect, a whole nation is now convinced that it’s better for the elderly to put up with a heat wave than cool themselves down with an electric fan. People have almost certainly died unnecessarily from this belief. These sorts of superstitions are a direct danger to people’s health, yet they often stand unchallenged. This is a lesson which needs to be learned by the citizens of modern nations if we are to make wise choices for the future. Unchallenged assumptions need to be challenged, and the most fatal path is to react with impression and instinct.

In the present world there is no more important economic or environmental issue than energy production. It is central to everything, and the choices we make about it now are going to have vast ramifications into the future. There is no more critical or serious issue in the world today than the energy question. Our collective choices concerning it have potency to shape the world of future generations, and the potential for disaster or glory is stark. Whether we like it or not, we stand at a moment in history pregnant with the potential for either. If we treasure the possibility of a decent future for those to come, we need to be able to make informed decisions with decent insight into the opportunities and problems of the options which nature and technology have laid before us.

For these reasons, nuclear power advocates have a duty to share what they know with others, assisting them on the path to understand what we have already learned to our astonishment; the near unlimited potential of nuclear power technology to sustain our global civilisation at well above the style to which the wealthy nations have become accustomed for such an immense time-scale it beggars the imagination, and its potential to do this with minuscule environmental impact. That story can be told verbally and with little reliance on mathematics or science, and many people will happily accept that. Others will look at the grab-bag of knowledge they have accumulated here and there, accurate or otherwise, and mark off their danger zones, and their impressions will be their impressions, and that will be that. But the issue is too critically important to leave it at that. We eventually reach a point where the nuclear story cannot be told in full without looking at the details, and venturing some way into the realms of maths and science. And so this is what we must do, and we must do it in spite of the impressions or instinctive responses people have to the subject, and in spite of protests that they prefer their impressions and do not want them challenged.

It is the responsibility of advocates to craft narratives which intertwine maths and science into a coherent and compelling story illustrating the reality and promise of nuclear power. We cannot expect people who haven’t devoted a certain amount of time to studying the issue to be across everything they need for a balanced view. The advocates must do their bit to bring them up to speed. But the effort is wasted on someone who refuses to consider this input in the first place. There is also a duty on the part of those to whom the outreach is directed, to meet us part of the way and be willing to consider a few simple arguments and concepts needing some fairly basic maths. We’re talking about stuff like multiplication, division, percentages and maybe the occasional foray into ‘ten to the power of’. It’s a small effort, and the bounty of insight to be had at its end will repay that effort many times over.

Of course, the ultimate reason we have to take this exercise seriously is that real lives are at stake. With every decision we make about how we are going to manage our technological society, we are streaming the future down a particular path with quantifiable risks (and see first figure in the post, above). If we choose to continue with coal, there are certain things which will happen as a result, including an elevated risk of death from respiratory disease. This will ensure that there are a certain number of deaths which will result from that decision, and nothing can alter that. These deaths are real, the people are real, their families are real, and the consequences for all of them are quite real. The same can be said for all the choices we make. All will entail real casualties, real problems, real restrictions. If we are to make the right choices, we need to know what these real risks and issues are, rather than dwelling in illusion.

By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

25 replies on “Risk perception – of fans and fission reactors”

Following. By the way, one of the links didn’t make it through properly. it’s in the final paragraph, just before the phrade ‘quantifiable risks’, which should be the button for the link.

Ed: Fixed, thanks


Thanks Finrod – entertaining and informative article.Homo Saps has great inventiveness and especially so in the realm of self delusion.

The shrinks haven’t developed a psychoactive drug for that yet. I guess somebody is working on it but it would probably cause at least the same amount of collateral damage as the present crop of drugs.


A good read, thanks Finrod.

Risk assessment is something most people are very, very bad at. It continually amazes me the things that some people will do, just because they perceive it has a low risk (weaving through traffic while driving at highway speeds is one example that I’m sure we’ve all witnessed).



If only the right folk could be persuaded to read this article and the linked essay….

Thanks, Barry and Finrod, for giving this to us all.


Great article, thanks Finrod. Humour is often a good way of communicating touchy things in a constructive way. Well done.

Barry – I’m not sure if you’re aware, but I jut noticed there are “eco pressed” ads appearing at the end of all articles on BNC at the moment.


Very well written Finrod. I like your vocabulary as well…

I’d like to focus attention to a concept that is related and important: opportunity cost.

For example, not having fans to cool down people means either more heat deaths, or more airconditioning that indirectly kills people (not to mention emit more CO2) by fossil fuel electricity.

Another example, spending money in expensive photovoltaics only to burn 80% fossil in ‘backup’ (a term that may be the energy understatement of the century) when the alternative, investment in nuclear, can get us there almost completely with very little fossil ‘backup’.

The world at large is not considering opportunity cost in energy transition policy. That means we’re not taking the issue seriously, at all. Innumerate ideology, commercial interests and naivety triumph the world of energy policy making. Not a single country yet has a plan that adds up. Tres bizarre, but very few seem to be worried about this.


Another great example of flawed risk perception is of course the recent Fukushima evacuation. The evacuation criterium is 20 mSv per year. According to the theory of linear-no-threshold, for which there is no evidence but everyone uses it anyway, 20 mSv gives you a 0.2 percent increase in cancer (any type).

Now compare this to living in London: a 2.8 percent increase in your chance of dying, because of the pollution.

Even if we believe the linear no threshold model, this is 14 times deadlier than the 20 mSv limit, yet no one is talking about evacuating Londen.

This nuclear dramatizing exceptionalism is even more stark, when one realizes that nuclear powerplants powering electric vehicles and factories in Londen can solve most of the pollution deaths.

This is the opportunity cost that we are paying for our radiophobia.


What about paper fans?


I guess they would present the same danger as electric fans, provided you could achieve a comparable airflow. You might need many people with paper fans to do that. And they’d need to be standing around fanning you while you slept. You’d probably need to pay them for this service. It would be an expensive way of doing things. But given all that, yes, I expect that the results would be similarly perilous to sleeping with an electric fan on. Actually, probably much more perilous, since people are autonomous, and one of your fan-boys might flip out and attack you as you sleep.


Huon’s link kind of blows this notion.
I’d known about this problem — growing up before air conditioning, when it happened more often — and I was going to jump in, but Huon nailed it already.

And nobody responded. Did anyone read what he pointed to?

—–excerpt follows—-
Don’t believe the Korean? Would you believe the U.S. Environmental Protection Agency? This pamphlet from the EPA, at pages 49 and 51, clearly states the hazard of using portable electric fans during high heat. It specifically says “Portable electric fans can … increase the circulation of hot air, which increases thermal stress and health risks[,]” and “DON’T use a portable electric fan in a closed room without windows or doors open to the outside.
Or how about a climatology professor who works for the National Weather Service? In an interview with NPR about extreme heat warning system, Dr. Kalkstein specifically mentions the danger of fans in a hot, enclosed room (At 13:45 mark): “One piece of advice we tell them not to do is to sit in front of a fan in a hot apartment because it has a convection effect.”
—-end excerpt—-

That’s from Huon’s link:

Fact checkers — badly needed for credibility.

Barry, seriously, please, can’t you find a reference librarian/science librarian, uninvolved with the nuclear power issue on any “side” — who could just glance at your columnists’ work before you publish it and do the very basic simple fact checking?

Any newspaper would have done that, back when facts mattered.

The people you’re trying to convince — the reluctantly willing — still care about facts and can be convinced. Using facts.

Enthusiasm without facts that can be checked and found correct isn’t going to convince anyone who isn’t ready to sign on.


Hank Roberts:
(i) This is a blog, not a peer-reviewed journal, and will never try to be what it is not. Credibility is up to the reader to ascertain, and if you find the content here incredible, that is fine, it’s your decision — just try not to always sound so damned preachy!

(ii) I’m not ‘trying to convince’ anyone — that moment of grand delusion has long passed me by. These days, BNC as much a place for topic-focused and moderated discourse on climate change and sustainable energy, as it is an information site. I’m NOT an advocate, and I’m not trying to twist people’s arm on energy matters. Such things are decided in much more complex ways, as you must surely be aware from your time commenting on RC and other locales. At most, this site will provide material to inform a long-term decision-making process.

(iii) On fan death, what Geoff Russell said.


Great piece Finrod and yes Hank, I did read the link. But the fact that fan death may be possible under the right conditions makes the relevance to the nuclear issue even stronger. Radiation can kill people, but the story is complex. The implication is that radiation needs to be treated with respect and public education improved … we
don’t need ignorance and fear. I only just saw Liz Haye’s 60 Minutes piece and it parallels the fan death story very well … any grain of truth about radiation was buried in a mire of ignorance and panic.

Public education about complex matters is very difficult. When educators can’t tell the whole story they have to use analogies and blur the details. When a recipient of the message can’t understand it they make up a substitute story. Soon you have a full blown Chinese whispers game and the explanations of fan death are a beautiful example.


I had actually seen the articles Huon and Hank Roberts refer to while researching for the article. I noted that the circumstances under which fatalities were said to be possible were ones where the candidate was much weakened prior to falling asleep, and a good way towards physical collapse already. In fact one might question, if the candidate was that close to collapse, just how much responsibility a coinicidentally operating electric fan could be assigned if a fatality did occur. At any rate, I judged the linked article to be a deliberately contrarian piece with a certain comedy value. I guess others have other interpretations.


Just to comment on the linked article ‘proving’ fan death is real, this sentence stuck out for me:

Humans sweat, and when the sweat drops evaporate, the air around the body cools because of the evaporation.

Er, no, that’s not right. It’s not the air that’s cooled by evaporation of sweat, it’s your skin. The air next to your body becomes, generally, much more humid and warmer as a result of your skin transferring heat to it.

However, to say that a fan might aid in dehydration is, at least, plausible – but a person would definitely have to be in serious danger of dying of heat exhaustion for a fan to push them over the edge, because the breeze from the fan will constantly replace the moist air layer next to your body with new dry air, which will significantly aid evaporative cooling. That’s how a fan makes you feel cool.

Having slept in the breeze from a fan ever since I was a toddler (it can get pretty hot & humid up here in Queensland, and my parents got their first air-conditioner 10 years after I moved out of home), and having some knowledge of thermodynamics (thanks to my engineering studies), I feel on pretty solid ground when I say that, in my opinion, ‘fan death’ is not real.

The effects of heat on the human body are pretty well studied – and, of course, the impacts of global warming on this are pretty worrisome.
See this paper for example. I think a full copy is available from the UNSW here [pdf].

Which brings us back to risk. What’s the bigger risk – a meltdown causing contamination from operation of modern Gen III+ reactors, or a heatwave in a densely populated area like India, China, Sub-Saharan Africa, or even Australia or the US, where most animals (including humans, their pets, livestock, and native fauna) not in air-conditioned rooms literally drop dead of heat exhaustion? Such a heatwave in India, for example, could literally result in hundreds of millions of deaths – and I believe northern India is one of the areas of the globe that already gets dangerously high temperature/humidity conditions.

Sadly, I think it would take an actual heatwave like this to persuade some people that there’s a problem (similarly to sea level rise, droughts, floods, etc caused by climate change). And by then, it’ll be too late, of course.


It’s a great example of a real problem — affecting a very small, unusually vulnerable subset of the population in extreme conditions — for which both the explanation and the fix are understood but completely lost in the media noise.

> new dry air, which will significantly aid evaporative cooling.
> That’s how a fan makes you feel cool.


When no new dry air is available, in extreme heat — above body temperature air — running the fan will “increase the circulation of hot air, which increases thermal stress and health risks …. DON’T use a portable electric fan in a closed room ….” (from the EPA article linked above by Huon).

Similar physics: get into a car and face a foggy windshield in a cold rainstorm. People who don’t understand _relative_ humidity will set the car air to recirculate, and run the heater and fan. The humidity never goes down inside the sealed car. The fix — switch to bringing in outside air, heat it, lowering the relative humidity, and that will defog the windows. (Yes, in both cases, running an air conditioner actually does remove moisture from the air — these problems don’t happen with active cooling, only with recirculating air in a closed space).

I admit failing to avoid preachy/teachy, feeling there ought to be a teachable point in this kind of confusion — heat stress is real, is quantifiable, affects the most vulnerable who can’t either understand it or avoid it, and

“… heat stress imposes a robust upper limit to such adaptation. Peak heat stress, quantified by the wet-bulb temperature TW, is surprisingly similar across diverse climates today. TW never exceeds 31 °C. Any exceedence of 35 °C for extended periods should induce hyperthermia in humans and other mammals, as dissipation of metabolic heat becomes impossible.” — the Sherwood paper cited by Bern just above.


IMHO Risk perception is only irrational at the individual level.

For species survival some portion of the population has to take extraordinary precautions against all potential risks in order to insure that no low probability event wipes us all out.

We need someone to jump up on a chair and start screaming at the sight of a mouse since history tells us that rodents can carry deadly disease that is easily transmitted once it jumps to the human genome.

Of course we have plenty of people that jump up on chairs and start screaming at the sight of a mouse even though science tells us that mice are mostly harmless.

We also have people who won’t go into a building if a microwave is in use, even though science tells us microwave ovens are harmless.

The challenge with nuclear power is finding a way to accommodate those people who are serving an extremely unlikely extreme event species survival function without burdening the rest of us.



Enough small particles of dust and what not in the air that we shouldn’t increase that risk in any way; move from downtown Tokyo to the most radioactive part of Tohoku to significantly decrease LLE.


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