IR contactless temperature guns

very little I suspect, they do vary in the angle of the measuring "cone"

We mow know that this is a pointless thing for many viruses and bacterial infections, unless you catch it at the exact time. Be better off getting that test system more reliable and faster than faffing about with infra red temperature guns. Brian

Andy Burns explained :

My DIY gun reads around a 3 degrees low of normal body temperature, when checking my forehead. If there really is no difference, they must be manually applying an off set to the reading.

stick some black insulating tape on your forehead?

The main difference is that the ones intended for use on humans or animals are calibrated for the emissivity of human skin which isn't all that close to being a black body for thermal radiation.

For precise none contact work you put a black sticker on the target that has the right emissivity for the measurement device you are using. But for mass screening it is easier to fiddle the detector to match "skin".

Martin Brown explained :

I knew about the black tape trick, but never saw them stick tape on the people they were checking.

The black tape has to be the correct type. Some black tape may actually act as a mirror to IR and so you are measuring the temperature of what it is reflecting rather than what it is attached to.

What about people with varying degrees of black skin ?

Black in this sense means black in the 3-20um thermal IR band which is quite unrelated to the apparent colour in the visible spectrum.

To a first approximation almost anything opaque and non-metallic is almost black for thermal IR but when you are trying to measure a small temperature difference precisely on a background of ~300K you have to compensate for the fact that skin is not an ideal opaque emitter.

Notable examples where opaque things are transparent to thermal band IR are black bin bags and thin pine cladding. Conversely window glass is transparent in the visible (obviously) but opaque to far IR.

Doesn't help:

I disagree, it is useful as a rapid mass screening device that requires no skill. I don't know how effective it was at airports etc. in the Far East, but certainly better than nothing.

Some companies are starting to put TV monitoring systems on main office entrances, these will be backed up by trained security staff using a proper medical "ear-thermometer" on anyone who triggers the system.

It's actually reflective. Had a play with a thermal camera the other week, have capuured still of my thermal reflection in a glazed door.

As to the OPs orginal question I would be very surprised if the IR thermometers generally being used to check for fever are anything other than bog standard ones.

The actual "temperature" reading the device produces isn't that important you're looking for an elevated temperature. Having played with my IR thermometer and measuring skin temperature from 1/2" or so it's moderately consistent within +/- 0.2C. That, in theory, ought to be enough to give an indication if someone has a fever of 1 C above normal. Trouble is depending on the exposure of the skin, ie recently covered or not there is several degrees difference in indicated temperature.

Conclusion, it might pickup on someone with a fever but I wouldn't like to bet on it. A 1 degree C fever makes you feel really grotty, it might be more reliable to look at someones eyes for "fishyness" and their general demeaner and combine that with the IR thermometer reading.

Or point it up your nose, or into the back of your throat ?

The Chinese don't bother with any of that. They just pick out anyone with higher temp reading than the rest.

NT

Do they have settings for different skin colours? Like before and after a holiday in the sun? ;-)

They may have a resolution on 0.1 deg C, but accuracy is a different matter and on mine is stated as +/- 1 deg C

Oral , ear canal or anal temperatures are usually the best to match "core" body temperature which is usually quoted as a normal value of 37C .

Brits who have turned that peeling lobster pink colour they seem to aim for on holiday may well show up as feverish on a temperature test.

My lidaldi thermometer reads 36.x in my ear or under my tongue, where x varies from .3 to .7

My cheapo black/yellow "gun" thermometer varies between 30.1 to 33.6 when looking at my forehead, throat or ear, sorry no black tape to hand.

...which if Chinese means +/- 100C

NT

thankfully they're not testing those