Microwave ovens and their hazards | Hacker News Reader

Microwave ovens and their hazards

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82 pointstrifit94 comments

Yes we need documentation like this.

When I was younger I worked in a warehouse. In that warehouse we had a break room. In that break room we had a microwave that was not in good working order. The mechanism that would stop the machine from emitting microwaves when the door was opened had failed, and instead of fully disabling the machine out of safety it would allow it to continue to run with the door wide open.

One day a coworker had been heating up some food and wanted to check on it, so he opened the door while it was running and stuck his head inside. Right inside. I had to holler at him to stop and pull his head out. Of course he was in no immediate danger, but I'm sure rotating all those water molecules in your brain can't do much good... those things do bake potatoes after all.

The biggest danger is generally to your eyes because they contain significant water content but lack the circulatory cooling found in other parts of the body due to the need to be transparent. Looking into a running microwave with the door open can pose a cataract risk.

https://www.fda.gov/radiation-emitting-products/resources-yo...

Oh, yes.

Think of what happens to the clear "white" of an egg (proteins + water) when you heat it up.

Which clear parts of your eyeballs (also proteins + water) would you be okay with that happening to?

And if you are a man, your balls - which must be kept below body temperature - even raising them to 37C/98.6F will reduce fertility - heating them with microwaves goes far beyond that modest risk.

Interesting. I wonder if looking too closely into a fire carries the same risk.

Infrared eye protection is important for glassblowers looking at molten glass [1]. Back of the envelope math suggests that an occupation that required staring at an intense fire for long periods of time would violate the same workplace safety thresholds, but I have not been able to locate any studies that specifically investigated looking at fire.

There are a surprising number of different jobs that involve staring at incandescence from molten glass or metal, but I think the most interesting is an operator of a disappearing-filament pyrometer [2].

[1] https://www.sciencedirect.com/science/article/abs/pii/S02755... [2] https://en.wikipedia.org/wiki/Disappearing-filament_pyromete...

I don't know if that's just me, but I have a reptilian reflex to never put my head in any box or cavity of a powered device.

Take a good look at your hands. Hold them both up, turn them over, study the fingers and the palms and the wrists.

Now decide which one you could stand to do without.

That's the hand you stick into cavities of powered devices.

Machinery maintenance tip: before you stick your hands in, hit the go button. You should know that nothing is going to happen when you do, but you should do it anyway in case you're wrong.

I mean, in all honesty, when I occasionally find myself stopping and considering for a minute whether something I'm doing is safe, if I do decide "eh, it should be fine," I will switch to using my off hand.

personally i'd use sticks unless I need finger precision

In construction, it’s “never put your hand where you wouldn’t put your dick”.

I forget which either ravens or crows are the same way one of those birds won't put their head in any enclosed space.

I've often wondered about putting it between two bluetooth earbuds or next to a cellphone...

I don't know what the orders of magnitude power are, but I wonder about power vs time.

phones are sub 5w, even assuming it's a linear relationship you have 100-400x time less energy

A reflex nobody could fault you for having, to be sure.

Leave the rapid heating radio waves for the roti.

Radar operators in the Arctic learned that they could stay warm by standing in front of their antennas. The first microwave ovens were called "Radar Ranges".

My grandfather was an EE involved in early radar/microwave comm research and repeatedly used the beams to warm his hands and feet when in the field. He was exposed to who knows how much and developed serious sensory and circulatory problems later in life, as well as an unknown brain issue.

He was also around some of the overly-exuberant government tests of troop exposure to the immediate after-effects of atomic fission.

https://upload.wikimedia.org/wikipedia/commons/7/73/Exercise...

There is a long standing dispute between WW2 engineers at Raytheon vs. those at the UK's Telecommunications Research Establishment [0] about who was the first to cook sausages on a radar set.

(I previously worked at one of the modern successor organisations to TRE. I distinctly remember as a very young software engineer being told by an elderly staff scientist that his purpose in life "was to help confound the Queen's enemies and keep the poor bugger on the battlefield alive whilst he did so")

[0] https://en.wikipedia.org/wiki/Telecommunications_Research_Es...

The fact that these guys are still alive is pretty strong evidence for how safe non-ionizing radiation is, even at high strength.

It's all a matter of degrees. People love to bathe in sunshine, but when someone builds a mirror powerful enough to boil water, it would be wise to keep your head and limbs well out of the focus.

At least when you're not sticking your head into a box that is meant to contain those waves and concentrate them in order to heat up water-laden organic matter.

in my experience they seem to be more efficient at super-heating ceramic plates than water filled organic matter which still manages to be frozen in the center

The key is to use programs for cooking rather than max power. The programs will use variable power levels to achieve more "even" cooking/reheating.

I read that the heat/cool heat/cool pattern of the 50% power level cooking for twice as long helps the heat to dissipate into the food, melt the ice crystals, and gives a better overall experience for taking 2x the time to cook the food.

I've not put that to the test myself with any scientific rigor but I have noticed better results with it personally.

Ice is far less absorptive than liquid (out I think even gaseous) water. First thaw, then cook.

Also, use borosilicate glass instead of said ceramic.

One of the first uses of microwaves for heating was to humanly heat hamsters that had been cryogenically frozen.

Back in college, there was a food truck on campus that had a microwave in it where the owner had cut a hole in the door. They would set the timer for 99 minutes and just take stuff in and out whenever it was ready. Much faster than constantly opening and closing the door.

Yikes. If you saw something like this, you could probably legitimately file an FCC complaint (in addition to a complaint to your favorite worker safety bureau). That was probably causing all manner of EMI in 2.4GHz

fuck it's so good I didn't know about this when I was a cook.

Microwaves have two door switches to stop this happening.

If one fails, the microwave will still whir and the turntable turn and the light on, but the actual magnetron will be disabled. That's probably what happened to yours. If he actually had his head in an 800 kilowatt microwave turned on, even for 1 second, I doubt he'd have any vision left.

> 800 kilowatt microwave

I hope this is a typo...

Maybe. 800 kilowatts means there would be nothing left. I'm sure that there's some industrial- or factory-grade microwaves that are 800 kW.

Keep in mind that microwaves have lower frequencies than visible light or even infrared.

Radio -> Microwaves -> Infrared -> Visible light -> UV -> X rays -> Gamma rays.

I wonder how this happened. I repaired two (consumer-grade) microwaves, and both of them had 3 independent switches:

- one was sending signal to controller

- second was cutting power to something (presumably magnetron) when released

- third was short-circuiting magnetron when released, it would cause fuse to blow if it ever got energized

I assume the mechanical parts were aligned such that if you open a door, the second switch was released before the third one.

The point of the design is that firstly if you try to defeat the interlock you will cause a short circuit, unless you carefully activate the switches in the proper order as the door would, and secondly a programming or other fault in the controller can never activate the magnetron with the door open.

I remember when I was younger looking into a microwave that was on, after the door had been smashed (don't ask). I remember my vision going all wavey, proper freaked me out. From this article it sounds like the water in my eyes was being rotated, which is kinda freaking me out again.

Wow... that's scary. But I think that when the article talks about water being "rotated", it's talking about individual water atoms, whose rotation would be too small to see.

I imagine that the waviness would actually be due to the change in refraction due to the microwave's uneven heating -- like the waviness seen in the air just above a hot road, or the faint ripples seen at the bottom of a pot of cold water, when you start to heat it on a stove.

When I was in my teens, we took a class trip to a nuclear reactor being built (never completed) in southern Indiana.

I’ve long regretted I didn’t have a camera with me to capture the large sign on one gate that read (paraphrased): “Danger: Microwaves on premises”

I wasn’t sure (still am not) whether they were referring to something industrial, but the thought that household microwave ovens at a nuclear power plant were sufficiently hazardous to require warning signs like that amused me.

The sign was most likely for pacemaker patients.

Are modern ones still susceptible?

I was always under the impression that microwaves posed a hazard to pacemakers because of the magnetic fields involved, not the RF emissions themselves.

Pacemakers use magnetic switches inside the sealed device for programming and/or battery shutoff. Lots of things involve pacemaker warnings, including iPhones with MagSafe charging ports in the case.

Aren't they encased in some bio-compatible metal, essentially making them a faraday cage that should be immune even to direct exposure?

I believe they use microwaves for inspecting the welds on pipes and such.

That's usually x-rayed if it's critical infrastructure AFAIK. Dad was a pipe fitter for Imperial Oil.

Depends on the size of the cracks you want to observe. For aircraft they use ultrasounds. I assume you dad used x-ray because methane and H2 are extremely small (they can’t be contained in, for example, water pipes, so the same goes for diagnostics and wavelengths).

Hot crude and hydrochloric acid under pressure are two I remember from his stories. He said they checked for hairline cracks. What that actually meant in practice for measurements I’m not sure.

I've done a fair amount of weld inspection / NDT. X-ray would be the only radiation based method used on a construction site. This would typically be done in batches and require the evacuation of an exclusion zone.

Supposedly you can test for this using a wifi device since the frequencies are similar so I threw this together https://ismymicrowaveleaking.isotropic.us if anyone wants to try it. No clue how accurate it is, seems to work for my sample size of 2 microwaves. Phone had to be on 2.4ghz wifi or the signal was unaffected.

Consumer microwaves use the same frequency as WiFi (~2.4Ghz) and leakage can be measured with EMF meters.

We need an open-source database with test measurements of microwave ovens:

  - new devices (does max leakage vary by country?)
  - annual measurements of door seal decay

Worth noting that most microwave ovens are made by two companies (only one, in the US), other than some high-end models.

See https://twitter.com/wirecutter/status/1263549250719416321?la...

Panasonic microwaves besides the very cheapest ones are unique to Panasonic and much better than the Midea models. I no longer own a microwave (due to kitchen space, not ideological opposition) but when I did, the Panasonic microwave I owned was noticeably better in every way than any microwave I had owned prior (which it turned out were all probably Mideas).

Imagine being able to get a product reliable at that scale.

huh it used to be Sharp that made most of these OEM/ODM microwaves

I have a 5 year old microwave purchased from a retailer with a reasonable expectation of quality (Costco) with no visible issues with the door seal that significantly interferes with 2.4 Ghz WiFi. I'm sure my neighbors don't enjoy the occasional internet issues that must result.

Yeah, I was hosting a zoom call once and everyone got kicked off immediately when my flatmate used the microwave to heat up his lunch.

Also Bluetooth. My microwave tends to interfere with my Airpods.

There was an HN post a year or so back about the microwave oven used in the lunch room, of a SETI facility, or other radio astronomy setup, that befuddled everyone by interfering with the received signals. No one could detect the source, which occurred at certain 'periodic' times of the day. Until it was tied in with coffee breaks and lunch time. I found this with a quick search: https://www.theguardian.com/science/2015/may/05/microwave-ov...

I know this is tangential-- but does anyone know what the normal failure modes of microwaves are like?

20 years ago I microwaved some leftover macaroni and cheese from just a few seconds-- and it came out absolutely charred.

I was confused but then noticed the microwave making an awful sound--a low rumble--it wasn't supposed to be on at all. Then the sparks started, then the smoke. Unfortunately the plug for it was behind a refrigerator so I ran to the electrical panel to turn the house power off.

I figure some mosfet or something that controlled power must have failed closed or something. It most likely would have burned the house down if I hadn't happened to be right there.

a major hazard missing from the article: high voltage transformers and capacitors inside can easily generate and store north of two-thousand volts. metal scrappers should take care to de-energize the circuit before diving in.

Newer microwaves don't use bulky HV transformers + voltage doublers for the magnetron anymore and instead use high frequency power supplies + step up transformers, and are noticably lighter

Yeah that plus they often contain beryllium oxide which is dangerous to inhale as a dust.

My understanding is that this risk is overstated. BeO dust can be dangerous, but new microwaves no longer use it as an insulator, and the amount of dust which is likely to be produced by breaking the insulator in older microwaves (rather than deliberately grinding it to a powder) is minimal.

I had the shameful experience of breaking one of this rings. I got so scared from hearing about BeO that I mailed a bunch of safety hazard chemists and doctors. Most of them told me BeO is not used anymore in most kitchen appliances MWO and that it's most probably AlO which is enough to dissipate consumer devices' power. BeO was used in high wattage or military devices. After digging magnetrons manufacturer data sheets I found mentions of AlO and Chromium but no BeO.

Could be. In my estimation - for the vast majority of even technical people it is probably best to dispose of a nonfunctional microwave rather than attempt a repair.

Caps shock can happen so easily. Lots of tutorials online on how to make a discharge rod.

I still have a dozen to make a 10kV ladder one day.

I find dishwashers to be surprising dangerous. They can catch on fire from the heating element and their failure rate is astonishingly high.

Perhaps American dishwashers are different, but EU dishwashers have 5 independent safety mechanisms on the heater...

1. It will only power up if the water level sensor detects water above the level of the heater. In many machines this is a hardware switch, not software+relay.

2. Power to the heater goes through the door switch. With the door closed, a fire in the wash compartment will run out of oxygen pretty quick.

3. The heater has a temperature sensor on, and software control to turn the heater off at a set temperature.

4. The heater has a thermal fuse, which over 150 C will permanently cut out the heater.

5. The heater isn't exposed on the bottom of the dishwasher where things could touch it - instead it's under a grille or embedded in a pipe that water flows along during washing.

I know all this because my dishwasher caught fire... But it wasn't the heater but a power supply wire to the heater which had a corroded connector. Turns out many years of vibration and steam is hard to design connectors for...

Yep. Happened to me. Came home with my wife after visiting my brother and the house was full of smoke.

Thankfully no flames that could spread.

I had a dishwasher that probably had a bad valve that caused it to leak water all over my kitchen floor while I was on vacation. Needed to replace the hardwood floor because it swelled up. (Ironically, my home insurance paid to replace everything except the dishwasher. Sigh...)

I’ve met folks who’ve worked in that industry that won’t leave one running unattended.

The manual to my fridge says to never leave it running unattended...

This is actually because the compressor can fail, generating heat and so possibly catching fire.

Wires can also melt.

I've seen far more than my share of appliances-turned-bonfires. Shorted wires, terminals, animal fur. Magnetrons and capacitors running amok. Those are especially fun when the microwave is mounted into wooden cabinets. Dryer belt pulleys freezing up causing friction rubber fires.

The dangers abound, they just are never thought of until it happens.

Now you have the extra fun of ICUs being on backorder 6+months (9/10 failures on all new models are ICU/touchscreen board failures).

I'd really hate to be an appliance technician right now.

I think there is irony in having an appliance that you cannot safely take your eyes off of.

Interesting. What's the actual root cause of that?

In my case the dishwasher's program cycle got stuck and it kept heating up the water till it had all evaporated.

I would usually nudge it along when it got stuck, but that time I had been out and forgot about it. I would have never expected that to happen but in hindsight I feel pretty stupid for not replacing the dishwasher immediately when it started acting up.

To be honest, I'm not sure. I can say for a long time, refrigerators were very dangerous and would often kill people. It's why Einstein co-patented a new mechanism for refrigeration.

Likewise, maybe there's something particularly challenging about designing heating elements to work in a watery environment that makes dishwashers subject to failure.

It also doesn't have the same global popularity as more common appliances like a dryer, so perhaps the failure rates aren't as well known, except among the affluent and restaurant owners.

Maybe unsecured plastic falling onto the element prior to the dry cycle.

Sabine Hossenfelder has a great explanation of 5G controversy[1] that is somewhat relevant. Explains why it is probably not dangerous, but also indicates why some additional study is warranted.

[1]: https://www.youtube.com/watch?v=FBsP-bmDLOo

What's the latest science on microwaving plastic containers? Many now say "microwave safe" on them... did something change, like the research or the plastics used?

Many of my friends still refuse to do it, but I'm not sure if that's still well-founded. My thought process is: well, the lawyers let 'em explicitly print "safe" on there... so they must be pretty damn sure.

The safety they're referring to is whether the container will melt. But plastic leaching into foods is still a problem as far as I know. So I use glass containers for leftovers that I take to work, for example.

I don't think they have to be pretty damn sure that they're safe.

They only need to be pretty damn sure that they can't be proven to be liable for damage in a court of law.

I think the distinction people need to make is between heating in plastic and cooking.

>this would pose no known health risks

Feels like I've seen these words so many times before...

my gf's mom here in Colombia wont allow microwaves in the house since 'they make you sick'. she also believes having hair wet for too long will make you sick

UHF microwave gun: https://www.youtube.com/watch?v=FIU8WZR9DNA

Getting burned when taking the food out is a far bigger risk.

is this anti-science, since microwaves are non-ionizing therefore cannot cause cancer or any other ill effect at low doses?

The article seems to be focused on the potential risk of interfering with medical devices using the same frequencies for communication. The more obvious danger of a microwave oven is that you must not stick your hand inside a microwave with a defective door sensor while it is running as it will cause heating in the same way that it can boil a cup of water.

I will note, however, that the statement "microwaves are non-ionizing" does not automatically imply the common follow-up that "the absorption of microwaves cannot have any chemical effect other than indirectly through heating". This is evident, for example, in that proteins in the human eye undergo a chemical change in response to absorbing non-ionizing red light. Whether there is such a thing as a non-thermally microwave-driven chemical reaction is an open question in chemistry [1].

I feel the need to clarify as an addendum that nothing in this post suggests any danger associated with the use of low power microwave radiation from consumer wireless communication electronics.

[1] https://en.wikipedia.org/wiki/Non-thermal_microwave_effect

From, well, reading the article, I'd say no.

Yeah, this article is more for people who had a random thought about the dangers of microwaves and wanted to see if there was any truth to it.

It should put you at ease to know that as long as you don't microwave yourself there isn't much to worry about.

Non-ionizing radiation is certainly able to have effects on biological systems, and there is no reason to believe that effects are strictly neutral or positive. Calling these facts 'anti-science' is blatantly asinine.

Cooking food by frying or grilling is probably much more of a health risk, not accounting for food being heated in plastic packaging.

Careful observation and investigation is never "anti-science" by definition.

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