Good to see an article calling this out. Temperature-screening might catch a few people who know that they have a temperature (or are just not feeling well) and are going to "tough it out".
Here in the Portland, OR area I've noticed a definite change in how many people are wearing masks. At the grocery store, 2 months ago there were about 5% of the people not wearing masks and they all tended to be men in their 30s and 40s. At convenience stores in more suburban area, I was the only one in a mask. Now it seems like 100% of the people are wearing masks.
Wearing masks, not temperature checks, is what seems to be our best option.
> Temperature-screening might catch a few people who... are going to "tough it out".
And cause others with symptoms to stay home in the first place with the fear that they'll be caught, wasting the trip (e.g. to LAX in LA traffic), keeping them out of the secured area & also off transportation to that area.
Because it IS the best option. Temperature checks are theatre, and don't matter when it only takes one asymptomatic, maskless person to spread a deadly respiratory illness.
Are you reacting to somewhere that was doing temperature checks, but not requiring masks? Relying on temperature checks alone is clearly foolish.
In my experience, I've only ever seen temperature checks at doctor's offices and hospitals, where they also have mask policies so "thorough" that I sometimes have to argue to keep my P100 non-glasses-fogging respirator on.
I agree completely on masks being preferable to this, but I wonder whether it may have some utility anyways, because even if it does not catch many asymptomatic people, if it is widely deployed and it catches _some_ people, those people don't go on to spread the virus, and then if you deploy those measures broadly, you have managed to halt a few potentially exponential sources of spread.
I should hasten to add that I'm not an epidemiologist, so I don't know whether this is true. But my intuition suggests that even if this is just partially effective it might still be worthwhile in the context of national efforts to control the spread, which is a numbers game.
I think this is a crucial distinction between "security theater" and "hygiene theater" -- security risks are not contagious and don't have the same potential for exponential growth that virus transmission does.
As a doctor, I really do think this is ‘hygiene theatre’ (that is, forehead/IR temperature checks).
Last week I rocked up to operate at a hospital I irregularly work at which has recently introduced checks (as opposed to all public hospitals which have had this in place since March).
In theatres we were talking about how useless it was. One of the nurses said someone tested high last week. They made the person sit in a chair for half an hour and then re tested them and granted them entry.
To some degree I get it. I mean, my state is only recording 15-20 positives a day across almost 20,000 tests so the pre-test probability is small. On the other hand, what’s the point of a policy if it doesn’t change anything.
Another aspect of ‘hygiene theatre’ - when the apple stores reopened in sydney I happened to be one of the first back in (by coincidence). I visited late on the first day. I was initially impressed - security guard scanning, handing masks out.
Inside the sales rep who served me had a mask continually falling down his face and kept grabbing at his face and readjusting.
I eventually capitulated and told him he was wearing it upside down (metal bit across bridge of nose needs to be squeezed).
Mask hygiene is important but pretty much everyone is so slack with them that, whilst they may be decreasing aerosolisation, they would be actively increasing spread of body fluids on surfaces, since so many people put a mask on and then immediately give up hand hygiene.
> One of the nurses said someone tested high last week. They made the person sit in a chair for half an hour and then re tested them and granted them entry.
While 30 minutes seems excessive, this makes sense. Your surface temperature is heavily biased by your environment’s temperature. Letting one settle in a controlled environment to test is reasonable to see if it’s really a fever (temperature will stay elevated) or due to environmental factors.
An issue is that anyone could ice their forehead in advance and beat the test. Dunno if too low of a temperature triggers a fail. In theory, everyone should have to sit in a controlled environment before forehead testing, but at that point, may as well do tympanic checks.
(Among many other issues, like the massive variance that’s probably accepted because of unreliability of surface temperatures as a proxy for internal temps)
It’s winter here now.
It’s not true that a ‘true fever’ will keep temperature high. On night shifts when I am called to patients that are febrile (using more sensitive tympanic or sublingual thermometers) I often ask them to check again in half an hour to kick it down the road (at which time they are generally non-febrile) provided they have a known cause and are on adequate treatment. Although the Pathogenesis of hyperthermia in this instance is usually from a slightly different cause (ie bacterial rather than viral)
I biked to a non-doctor appointment in 80+ degree heat recently. A guy thermometer-gunned my forehead before coming in. I was outside and visibly sweaty, but I still had to warn him that given the circumstances, my temperature might appear a bit high. I don't know if people are really thinking through any of this.
Did it read high? I have been checked by IR thermometers hundreds of times and have never tested above 36.9C which seems to be the gate temp around here. I too have sometimes been hot and sweaty and it didn't seem to affect the results much. I cannot even enter my own apartment building without passing an IR thermo check.
I wonder how much of a difference biking made. Generating your own breeze may balance things out.
Right now where I am, air conditioning isn’t common, but it was slightly above body temperature at the peaks of each day (I guess 100F). I wonder how that worked out with scans.
From what I have read, you are most infectious in the 24-72 hour period before experiencing any symptoms.
Given that the time from infection to symptomality is as short as 48 hours, this means it may be possible to be infected by someone before either they or the person that infected them has started to show any symptoms.
There's a subtle distinction between being most infectious and infecting the most people.
You may be very infectious when symptomatic, but you're likely bedridden and the few people around you are taking some precautions.
On the other hand you may be less infectious while presymptomatic, but live a normal life, effectively infecting more people right before you "get sick" yourself.
Not to mention that OTC analgesics do a pretty good job at controlling fever. Don't feel well? Pop a tylenol and your fever will come down significantly for a few hours.
Now that likely won't work if you're in the throws of a Covid infection, but in the first few days when you're not sure if you're really sick? It probably does a great job of masking fever.
If you're reasonably healthy in general a fever(under 42°C) might be worth enduring for the health boost. Treating influenza by lowering a fever with antipyretics increases the odds of death in animal studies and in humans similar treatment has been shown to prolong recovery time.[0]
That's awfully high: You should be seen well before that, child or adult. [1] I have only had such a fever once in my adult life - and I had serious cognitive defects. I couldn't drive. I fell asleep while while waiting for the doctor, who proceeded to have me take 800mg of children's liquid ibuprofen and kept me there to make sure my fever started to go down, otherwise they were going to send me to the ER. My fever was 103.1 (39.5C). I'd think at 42C, I'd be in serious, serious trouble.
All that said, a low-grade fever isn't all that harmful. I still tend to take something. I used to try to tough it out before the experience above, but also found that without the body aches and headache that comes with the fever, I slept better while sick, even though I still would sleep for hours. I also tended to feel better a little sooner. Of course, this isn't data, and I've read the stuff about the beneficial fever before, but until general medical advice tells me to do differently, I'll stick to comforts.
I just transited through an airport, and it saddened me seeing how many people wasted perfectly good N95 and equivalents by poor fitness.
They’re no better than a surgical mask if you have a lot of gaps: they’ll filter nothing but your coughs. So little inhalation will be filtered because of the path of least resistance.
How's the actual mask use? The majority of people I see reuse the same one over and over, frequently touch it and adjust it, and then touch other things. I don't see how they're achieving much more than safety theater that way.
Does that matter? I thought the point of having the entire public wear masks is to stop the wearer's breath from spreading germs, not stop the wearer from coming in contact with germs.
Obviously medical professionals or other people who come in close contact would be better off using medical-grade masks in a hygienic and consistent way- but for the majority of grocery shoppers and such, I thought the purpose was simply reducing your ability to spread the germs.
How does it not matter? If their breath contains something that shouldn't be spread and they're actively touching the damp mask containing it and then touching other things, how does that not spread it?
you said that if people touch their mask or adjust it, "I don't see how they're achieving much more than safety theater that way." Covid is primarily airborne. If you prevent your breath and your coughs and your speech from spreading the germ and making it airborne, you're accomplishing a lot. And I feel like "damp mask" is a bit of an exaggeration. A hell of a lot more than "safety theater".
That's fine from a theoretical standpoint, but the reality is far, far different. People in general do easy, token gestures. They're not following proper procedures for mask use.
Citation needed. Reusing a mask that is already loaded with exactly the stuff you don't want to breathe will cause the material to dry as soon as the user stops wetting it with their exhale, and then pass through on re-use because it's under the filter size, even for an N95 which practically nobody is using.
There are good reasons they are called disposable masks.
Viruses don't live forever, and the current coronavirus is no exception. Current estimates for surfaces vary a bit, but I believe it's no more than 1-3 days for fabric. And of course, the decay is exponential. Finally, why would it matter if you inhale stuff you just exhaled? If you're already sick, it doesn't matter anyway. The mask is about you preventing others from getting sick; it only marginally protects you from other people.
The exhaled air does not go through the disposable fake mask.
Disposable masks that the majority of people are using are are not for reuse, and it says right on the box "not for viruses". The "oh but large particles they (aerosol experts) didn't think of that" thing is surreal to see people say with a covered face.
Yet those same masks are reused multiple times per day. Taken on and off. The multi-day exponential hand wave fails on reuse, the exhale re-hydrates the medium. Masks have a finite capacity before they are a net negative, and cloth IRL insanity is a growth medium.
The psychology of "wear a fake mask for others" is next level propaganda. It's right in line with the drastically more dangerous social contagion that person X knows better than person Y and therefore is righteous to force their ideas (medical procedures) on person Y.
Conditioning people to make medical decisions for others is too obvious, but here we are, fake masks and all.
It's a deadly religion, which repeats over and over in human history.
Every single claim you make here requires scientific evidence as in actual studies that demonstrate such effects. Are you seriously trying to argue that not wearing a mask at all is the optimal way to handle a highly infectious respiratory pathogen? You should be advocating increased availability of N95 or better rated masks instead. I believe the US has made a serious error in only allocating N95 masks to hospitals. The gamble is that surgical masks or cloth masks are enough, but they don't filter very well. Cloth masks are woven and have large holes everywhere making them only somewhat better than nothing. Surgical masks were never intended for serious filtration and don't even form a decent seal. BTW manufacturer claims or disclaimers are not evidence for anything in particular and are irrelevant.
> Good to see an article calling this out. Temperature-screening might catch a few people who know that they have a temperature (or are just not feeling well) and are going to "tough it out".
The article says that 30000 people were tested. 4 people were false positives, 0 people were true positives. This is called ‘many false positives’. Yet the people who actually had high temperatures were supposed to be at home anyway, right?
4 out of 30000 is not many, they are not real false positives and the design is flawed anyway because people are going to self select, as stated. So the article is just bullshit. Let’s not even go into the rest which tells some unrelated anecdotes about Ebola and other diseases that are not the same diseases and serve nothing but to indicate vague trends under the guise of evidence.
> Here in the Portland, OR area I've noticed a definite change in how many people are wearing masks. At the grocery store, 2 months ago there were about 5% of the people not wearing masks and they all tended to be men in their 30s and 40s. At convenience stores in more suburban area, I was the only one in a mask. Now it seems like 100% of the people are wearing masks.
This is a completely unrelated tangent. According to this anecdotal non evidence mask use has increased among some stereotyped group and in some establishments. Even if taken at face value this tells nobody anything about the effect of the masks.
> Wearing masks, not temperature checks, is what seems to be our best option.
That’s an opinion, based on nothing, which even if assumed true means nothing. To the writer something seems to be the best option.
That’s fine and maybe it even is the best option.
But does it really help to announce they jumped on the mask bandwagon before ‘men in their 30s and 40s’ and people in ‘convenience stores in more suburban area’?
The fake masks accumulate and concentrate particles in the users airstream. The large aerosols they do catch are dried and the contents can easily then pass through. They are not designed for viruses, and there is no strong evidence they do anything positive. I suspect they are a strong net negative.
At the very least they provide false sense of protection. If people want to be protected, they should use a real mask designed for viruses.
In situations where 100% mask compliance exits, they are still not effective.
Fort Benning: "according to Elizabeth Howe of Connecting Vets. About 640 recruits from the 30th AG Battalion and 2nd Battalion, 29th Infantry Regiment arrived at Fort Benning in May for training and were immediately tested for COVID-19. Four recruits tested positive and were removed from the group while the remaining soldiers were placed in isolation for 14 days without any training exercises. After the 14-day quarantine, they were all retested and every single one was negative.
Only then did the training commence – with the full panoply of obsessive social distancing measures, including mask wearing. You can imagine that there will never be greater compliance to these rules than during military training. Yet, just eight days later, after one recruit exhibited symptoms, 142 of the trainees tested positive. That is 22% of the entire group isolated and quarantined together. As they were young, none of them were hospitalized and most were asymptomatic."
And then there is the psychology, which is... more troubling to say the least. To the people promoting this pseudoscience, why not wear the fake masks forever?
It's security theater, much like the TSA. The temperature guns used at restaurants at gyms seem hard-coded to 97.7F but at least everyone involved can say they were "doing their part" to stop the spread. Whether it works is of secondary importance to making people feel like something is being done, even though in practice there's very little anyone can do.
I had an appointment recently where they took my temperature upon entering the building and the receptionist scribbled the thermometer reading down and circled it at the top of the forms I had to fill out: "28C". Which made me wonder whether she didn't notice that the reading she took was wildly inaccurate or just didn't care.
Future historians will wonder why various medical records show people with acute idiopathic hypothermia in the middle of July 2020.
> Future historians will wonder why various medical records show people with acute idiopathic hypothermia in the middle of July 2020.
You underestimate how many people in the database (from any time period) will have a recorded body temperature of 0, thanks to weak typing and buggy null coalescence.
if it's worth anything, as someone who's worked with lots of manually entered data, i expect to see 0.5% to 5% errors in most publicly sourced data collected in this fashion. i guess what I'm saying is, everyone actually professionally working with such on good faith knows its also stacked with a good proportion of bullshit/error.
>> Whether it works is of secondary importance to making people feel like something is being done, even though in practice there's very little anyone can do.
There might be stuff we can do indoors, but state government agencies aren't funding fast research into it - efficacy of filters and alterations to HVAC systems like installing UV-C lamps in them. Instead it's just "wear masks and take temperatures and get mad at people when they don't wear masks," which is perfect shirking of responsibility that large organizations love to do.
I would be surprised if a UVC lamp in an HVAC system is an effective way to spend money. You would need to retrofit in a sizable contact chamber
to get a large fraction of the air exposed to enough UVC, and you would need to deal with the facts that UVC lamps are power-hungry, not that long lived, and don’t like to be switched on and off frequently. And you would need to confirm that the UVC dose in use is effective against actual infectious particles.
In contrast, a plain old filter is likely to be extremely effective. A HEPA filter will catch almost all particles big enough to contain a virus, and a MERV 13 or better filter is quite good. All you need is a filter with enough surface area that a good filter has low pressure drip.
Almost all HVAC systems already have filters, so upgrading them is usually straightforward.
(I used to have a fancy electrostatic precipitator in my HVAC system. What a waste of power and effort in keeping it clean.)
>> In contrast, a plain old filter is likely to be extremely effective. A HEPA filter will catch almost all particles big enough to contain a virus, and a MERV 13+ or better filter is quite good. All you need is a filter with enough surface area that a good filter has low pressure drip.
The problem with installing a MERV 13 filter in a normal HVAC system is that the pressure (usually) isn't rated for it and can cause serious damage to the motor(s) as you noted, which is more common than people think (definitely the case in my home system).
UV-C installation is fairly simple; though I agree they are power hungry and you need to keep them on most of the time with maximum one power cycle per 24 hour period. They're cheap upfront and do work on normal coronaviruses, though.
Still the real problem is very little state-funded research on the topic, or development of some mitigation techniques for businesses that must run indoors. It's once again fairly useless bureaucracy.
Are they cheap upfront? I would imagine that just sticking a UV lamp in your furnace manifold by poking a hole in the side risks rapid UV damage to your furnace. And, if you’re going to slice up the manifold to make it appropriate for UV, you might as well put in a proper filter box instead. A decent MERV 13 or 15 filter from Aprilaire or another major vendor is not very expensive.
UVC lamps are relatively inexpensive to install. Usually they're put before and/or after the cooling coil where, if you have a clean coil, the light will bounce through the fins and increase the path length of exposure. If it's not clean, the UVC helps to break down anything organic over time and cleans them up.
With a few exceptions of more complex units all of the recirculated air spends time passing through the coil.
UVC doesn't damage metal parts, but does effect some materials that would be common in residential installations
Yeah not too bad - a few hundred for reputable ones. Need to keep it far enough away from the filter, obviously, or risk damage over time (or just change out the filter more frequently).
I liken using UV-C (potentially) and a good filter as a defense-in-depth technique, just like masks, social distancing, sanitizer, temp checks (all which do very little on their own, but in the aggregate help).
The response to COVID is fundamentally irrational, when we tolerate 'an invisible menance' that kills 100,000 Americans each year - much more than influenza: Air Pollution.
And those who don't die suffer all kinds of ill effects like asthma, reduced cognitive performance, infertility.
If we ignored COVID, but spent 2020 replacing all coal and oil fueled cars, trucks and powerplants, we would save 10x as many lives as would have been lost to COVID this decade, and make significant progress on climate change. A shameful missed opportunity.
I'm so sick of this response. Deaths stack. People are dying of pollution AND coronavirus. Just because pollution also kills lots of people doesn't mean COVID-19 isn't killing lots of people. Furthermore, last I checked, I can't die of pollution just from being in the same room for 15 minutes with someone who is also dying of pollution.
Not just marketing, but also politics. For example, early on in the pandemic, the Chinese government launched a push to reframe their response as a shining example for the rest of the world rather than a failure - and at the heart of this propganda effort was a publication explaining their approach so others could copy it, which claimed the whole thing was founded on mass IR thermometer screening to find people to test. (The document did not appear to be an accurate description of how China actually suppressed Covid-19.) The WHO then jumped on this, doing a tour of major Western publications to amplify China's claims. Journalists and politicians in Western countries also then merrily lept on this to go after governments they disliked, pointing at the lack of IR temperature screening to claim that their governments weren't taking it seriously like those in places like China.
China suppressed the virus not by IR scanning but by a well publicized system of travel restrictions and contact isolation/quarantine of anyone who had been in contact with a known case, regardless of whether they had a fever or other symptoms.
All this was public knowledge in February and can be verified by reviewing preprints and news articles from then.
> Journalists and politicians in Western countries also then merrily lept on this to go after governments they disliked, pointing at the lack of IR temperature screening
Curious, where did you see this? I can't remember seeing anything like that (but that's not to suggest it didn't happen)
Had a long conversation with my dog's vet about these thermometers. He used one I had not seen before, an intra-eye thermometer. It measured the temperature through the eye, the temperature based on light from the dog's optic nerve/retina. That is as close to the brain as one can get without cutting holes. Too bad it isn't allowed for humans yet.
It isn't hard to understand his difficulty with normal infrared thermometers: they don't work through fur. But in all animals (us included) temperature can vary many degrees depending on where it is measured. The face/forehead is not the best place if you are looking for 'core' temp. People with reduced blood flow (ie heart disease) will have much cooler foreheads. They may have a fever but their foreheads could appear rather normal.
I don't see any dangers, it is just a sensor detecting infrared light, but getting a device "human rated" is a complex process. There might not be a sufficient market to justify an $90 thermometer for humans.
The scatter plots of eye/ear/rectal temperature in this article are on point to the covid situations. Variations of +/- several degrees are observed, showing that IR temperature scans might be less than useful in detecting mild fevers. (Also, stubborn cat refusing to open eyes)
I found the reference [0] more useful to bring home the point made in the article that using these termperature screening devices gives one the false assurance that they can ignore the physical distancing and mask measures.
(i) Many thermal cameras and temperature screening products were originally designed for non-medical purposes, such as for building or site security. Businesses and organisations need to know that using these products for temperature screening could put people’s health at risk.
(ii) Temperature readings from temperature screening systems will measure skin temperature rather than core body temperature. In either case, natural fluctuations in temperature can occur among healthy individuals. These readings are therefore an unreliable measure for detection of COVID-19 or other diseases which may cause fever. Furthermore, infected people who do not develop a fever or who do not show any symptoms would not be detected by a temperature reading and could be more likely to unknowingly spread the virus.
I concluded a long time ago that most of the response to Coronavirus boils down to "security theater".
There is a subset of the population that wants to be told that whoever is in charge is "doing something."
Compliance with that "something" never seems high on the list. Honestly, some people seem to like that as it gives them something extra to gripe about.
There is another subset of the population who’s response to the threat is to deny the risk, accuse others of living in fear and pretending that it is a hoax.
The elephant in the room: my org tried a bunch of them and none of them (even the expensive ones) were at all reliable. If you're trying to discern between 98.6F and 100F... they were useless for that.
We desperately need cheap and simple means for mass screening of symptoms.
On the other hand, I have visited a DHL warehouse to ship some things in the Bay Area recently. Before I can enter, a guard at the door points an infrared thermometer at my forehead. "Eighty-five degrees! Come on in, sir!"
We've got an expensive infrared medical thermometer (purchased long before Covid) and it appears to be quite accurate for everyone in our family except me. According to it, I am pretty reliably dead.
But I think it effectively scares people to stay at home.
I remember having a hell of a fever during H1N1 going through a airport being scared they would catch me and I'd have to quarantine. Because it was continue or get stuck I continued, if it was just walking into a store....
A Customer of mine is installing an "AI-based temperature screening system"[1]. It's retailing for over $3K. Based on the manual it looks like a facial recognition access control security product (it can interface with the industry standard Wiegand protocol) with an infrared thermometer bolted on and a bunch of gross profit thrown in for good measure. The manual has the look of being a product rushed to market.
Presumably the "AI" part is that it knows not to set off an alarm if the person's cup of coffee has a fever, as has apparently happened at automated temperature screening points in China.
Oh yeah, I also had a technology evaluation on the job on this very topic. It's impressive how entirely inadequate IR cameras are. Glasses, no glasses, tilted head, hot food, ...
Sadly, we never got to the facial recognition stage because the client decided they didn't want to support it.
Just thinking out loud: Wouldn't it be possible to get much more accurate temperature readings by having people open wide and imaging the backs of their throats? This could still be done at a reasonable distance.
Of course, that would require people to stop long enough to take a reading, and would be useless for the products trying to scan crowds with an unattended camera and AI.
And, of course, nothing is really going to help you if the thermometers are inaccurate to begin with.
Yes, it does get much better accuracy. My company is developing temp screening/survey answering entry kiosks, we've put a lot of effort into getting higher accuracy than the generic imported kiosks.
Forehead temperature is highly variable with ambient conditions - sweating while walking in reduces surface temperature, but sitting in a low-humidity air-conditioned car with your face in the morning sun increases it. After as little as 60 seconds in a conditioned space, though, skin surface temp is pretty much normalized.
The camera scanners are using Flir microbolometers, which have a huge amount of noise/calibration variation, even on a per-pixel basis. The handheld guns and kiosks which require alignment are using thermopile sensors work much better for employee check-in, they have like a 1:10 spot size so you need to be within a foot or so of the sensor and intentionally align yourself with the sensor. The reading takes about 2 seconds to align and measure, which is fine for clocking in but, as you said, doesn't work in a crowd.
> Wouldn't it be possible to get much more accurate temperature readings by having people open wide and imaging the backs of their throats
Old-fashioned oral thermometers warn that they'll be inaccurate if you've drunk a hot or cold beverage recently. I imagine back of the throat thermometers would have the same flaw?
Most people put their masks on well before the entrance. Removing them at a choke point, in the presence of screeners who come into contact with hundreds of people each day, would be stupid. I would only submit to this if it were done outside in open air (not an enclosed lobby) from 10+ feet away.
I have an infared thermometer I've been using for cooking, and it often gives readings that vary quite a bit. Now some of that is measuring the actual variance of temperature at different points in the pan / pot / etc. But I've also pointed it at myself and got readings that weren't super consistent and definitely weren't core temperature - I think I usually see around 93 on people with it.
Generally those readings can vary a few degrees even if you are using it well. It's just not made to measure fractions of a degree.
So I was wondering how infrared could possibly work... Not really surprised it doesn't, but the stats at how bad it has been in the past (h1n1, Ebola) are shockingly bad. I guess I was hoping there was some medical variant of these thermometers, which is accurate in the 95-105F range, and the cooking thermometers just sacrificed accuracy for range. But it sounds like that's not the case.
The medical versions are different. They're not just reporting the actual surface temperature of the user's forehead. (Which is going to be a few degrees lower than core body temp)
They compensate.
I have an iHealth unit that Wyze was selling a few months ago. I check my temperature several times a day. I believe it's quite accurate. In the mornings it'll read 98.2˚F, afternoons I'm at 98.4˚F, and just before bed it'll read either 98.4˚F or 98.6˚F.
The fact that it's this consistent with the intraday variation gives me some confidence in it. But, granted, I have yet to have a fever. (That I know of!)
I'm not sure what it uses to arrive at the answer. It could be as simple as adding a fixed constant or multiplier to the forehead surface temperature. Or it could separately measure the ambient temperature and factor that into the radiant heat coming from my forehead to arrive at an answer.
The medical ones probably only take into account the average emissivity of human skin (which varies somewhat by race/genetics, which they do not account for).
During the start of the COVID pandemic, two of my friends traveled to Florida for a cruse. Naturally, they were quite worried about the prospect of getting on a plague ship in a foreign country.
Fortunately, the cruise operator was giving everyone a forehead IR thermometer scan, before letting them board the ship.
Unfortunately, at least one person ahead of them in line happened to scan in, and be let on board, sporting a cool temperature of ~85 degrees. I'm not sure if 'body temperature of a two-hour-old-corpse' is a symptom of COVID, but this did not ease my friends' anxieties for the duration of the trip.
If the temperature reads anything lower than 36C, you're doing it wrong and it's very easy for people to get a non-medical IR thermometer, start pointing at people and "checking temperatures"
That being said, it seems Covid-19 fevers are usually more intense than flu fevers (even H1N1 ones)
Back in the day we purchaised an instant in-ear thermometer, which can also be used for forehead temp. measurement too. The selling point was that with restless baby it's easier to measure the temp. Prior to that we used a common in-mouth (and possibly other side out) kind of beep thermometer.
Alright, 15bucks later, I tried it on myself... red alert, fever-fever, when in-ear. Hmmm, roll around forehead -- ambient temp.. The old-fashioned palm-to-forehead -- obviously, no reason for alert. Finally, test with the old in-mouth thermometer- all normal.
Reading the instructions only confirmed the unreliable nature of the instant readings. We kept it anyway for "backup", but for practical use continued with the "slow" in-mouth beep-beep, it also helped that it looked like a froglet.
Apparently, a success of in-ear measurement is a direct view of the eardrum by the sensor, which is not always possible, esp. with babies.
As someone with a documented medical issue which results in occasional fevers, but is dangerous to no one but myself, I absolutely will throw a fit if I'm ever denied entrance to anywhere on account of such a fever, and I'm not ashamed to admit it.
Everyone else in this thread seems to be focusing on the problems with the probability of fever given that someone's infectious, when the real question is the probability that someone is infectious given that they have a fever, which might be due to anything else.
But medical discrimination is okay in 2020 I guess.
That was a pretty obvious theater. I know a case of people being positive just by driving in a hot day. All days are hot here, at this period of year. Unless you are literally on fire, Is an useless piece of junk
Wearing masks on the other hand is not a solution if people does not respect spacing. The disease is stoppable only by vaccines at this moment. Most of us will catch it before that. This is the reality.
Here in the Portland, OR area I've noticed a definite change in how many people are wearing masks. At the grocery store, 2 months ago there were about 5% of the people not wearing masks and they all tended to be men in their 30s and 40s. At convenience stores in more suburban area, I was the only one in a mask. Now it seems like 100% of the people are wearing masks.
Wearing masks, not temperature checks, is what seems to be our best option.