mariomata
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Sterilization of Pi

Fri Mar 22, 2019 3:12 pm

Hi All,

I have a basic question about the Raspberry Pi Zero W regarding if this part can be sterilized. The main question I have is if the Raspberry Pi Zero W holds a charge (has a capacitor or something similar). The sterilization method in question uses explosive gas, so it is import that the Raspberry Pi Zero W cannot in anyway cause an ignition.

Thanks for your help!

hippy
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Re: Sterilization of Pi

Fri Mar 22, 2019 4:10 pm

mariomata wrote:
Fri Mar 22, 2019 3:12 pm
The main question I have is if the Raspberry Pi Zero W holds a charge (has a capacitor or something similar).
The Pi has lots of capacitors, all of which can potentially hold some charge. As to whether enough to be a problem with your 'explosive gas sterilisation process' I have no idea.

Heater
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Re: Sterilization of Pi

Fri Mar 22, 2019 4:14 pm

That is possibly the weirdest question ever to turn up here.

I don't think you can get a meaningful answer.

I imagine the Pi Foundation and the various manufacturers and suppliers are not going say "Raspberry Pi Zero W cannot in anyway cause an ignition." That would be foolish and open them up to litigation when something goes wrong. The Pi is a consumer product, not designed to be exposed to explosive gas treatments and such.

Random people here may well say it's a perfectly safe idea. That of course means nothing.

I suspect that if you want a guaranteed, explosive gas treatment proof device, you will have to pay many times the price of a Pi for it.

You may have to test the process for yourself and take responsibility for the outcome.

jdb
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Re: Sterilization of Pi

Fri Mar 22, 2019 4:23 pm

Never mind the stored charge (there won't be any after >10 seconds of power-off), what gas is being used? There are plastics/epoxies used in component encapsulation that may not play at all well with aggressive solvents.
Rockets are loud.
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NGC6543
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Re: Sterilization of Pi

Sat Mar 23, 2019 12:51 am

I don't think a charged capacitor is your real (potential) problem.

If you're using ethylene oxide (that's the usual suspect), you should be using a process to ensure a non-explosive environment in the chamber. EtO requires about 3% air to form a combustible mixture. The process needs to remove air from the chamber before the introduction of EtO. This is usually either by high vacuum or repeated stages of partial vacuum and nitrogen purging.

If the above procedure is not being followed, it should be!

EtO generally has good compatibility with most plastics, but there's really only one way to find out, and it isn't really to ask the manufacturer in this case. (Because production methods can change and I doubt ensuring EtO compatibility is high on the to-do list ;) )

There are also, usually, pre-sterilisation procedures to follow which might or might not be kind on the electronics.

By the way EtO is nasty stuff, for people that is. Chlorine dioxide is safer and, I think, also potentially suitable for sterilising electronics. Check out the medical fields on the matter (if that's not what you're in already).
Last edited by NGC6543 on Sat Mar 23, 2019 8:50 pm, edited 1 time in total.

echmain
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Re: Sterilization of Pi

Sat Mar 23, 2019 12:54 am

mariomata wrote:
Fri Mar 22, 2019 3:12 pm
Hi All,

I have a basic question about the Raspberry Pi Zero W regarding if this part can be sterilized. The main question I have is if the Raspberry Pi Zero W holds a charge (has a capacitor or something similar). The sterilization method in question uses explosive gas, so it is import that the Raspberry Pi Zero W cannot in anyway cause an ignition.

Thanks for your help!

Can you put the Pi in a completely sealed case and sterilize the case?

W. H. Heydt
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Re: Sterilization of Pi

Sat Mar 23, 2019 1:47 am

NGC6543 wrote:
Sat Mar 23, 2019 12:51 am
If you're using ethylene oxide (that's the usual suspect), you should be using a process to ensure a non-explosive environment in the chamber.
Interesting...I associate Ethylene Oxide with G. Harry Stine's writing about it as a rocket monopropellant.

Heater
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Re: Sterilization of Pi

Sat Mar 23, 2019 2:09 am

I was never much into chemistry. Now I find: C2H4O is a flammable, carcinogenic, mutagenic, irritating, and anaesthetic gas. It is so flammable and extremely explosive that it is used as a main component of thermobaric weapons.

This sounds like a lot of fun!

wh7qq
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Re: Sterilization of Pi

Sat Mar 23, 2019 4:05 am

Sterilized? If any human use is contemplated, I would expect the mods to have plenty to say on that subject. The country's regulatory agencies (FDA, etc.) definitely would.

As there are lots of plastics and other compounds in use in the RPi they need to be tested for survival with the actual sterilant you plan to use (which you have not bothered to divulge). As an example, endoscopic equipment cannot be sterilized with ethylene oxide or steam/heat and so must be cleaned and disinfected (not sterilized) in formaldehyde or similar material that would be incompatible with the bits. Some components cannot be accessed for sterilization and others cannot tolerate sterilizing conditions. RPis are cheap. Try one and see, but wait a while after shutting down the RPi, as suggested by the moderator in the above post. You might also want to wait for it to outgas before powering up, if something like ethylene oxide is used.

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Imperf3kt
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Re: Sterilization of Pi

Sat Mar 23, 2019 6:38 am

Stick it in mineral oil, no need for sterilisation then as the Pi is fully submerged xD
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Heater
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Re: Sterilization of Pi

Sat Mar 23, 2019 7:20 am

According to wikipedia Ethyle oxide is often used for sterilization of electronics:

"Ethylene oxide is one of the most commonly used sterilization methods in the healthcare industry because of its non-damaging effects for delicate instruments and devices that require sterilization, and for its wide range of material compatibility.[100] It is used for instruments that cannot tolerate heat, moisture or abrasive chemicals, such as electronics, optical equipment, paper, rubber and plastics"

Not that it would not be wise to test for adverse effects.

Just autoclave it. Pi can take 120C for twenty minutes :)

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default_user8
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Re: Sterilization of Pi

Sat Mar 23, 2019 11:03 am

All good information, but I think he is using the wrong terminology. I think he is asking if a Pi can be made intrinsically safe("it is import that the Raspberry Pi Zero W cannot in anyway cause an ignition"), not actually sterilized, as in "surgically cleaned". There are different ways to do that, one would be to use a pressurized enclosure which is used throughout the industrial world to create intrinsically safe cabinets for controls. Another would require your pi to be encapsulated in something that would make is intrinsically safe by means of eliminating direct contact with an explosive substance. You could do this by verifying operation of your pi, and then dipping it in epoxy, but that would create a situation where the pi would be a throwaway device as you wouldn't be able to change the sd card or any connections. Good luck with your project.
Two heads are better than one, unless one's a goat head.

wh7qq
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Re: Sterilization of Pi

Sat Mar 23, 2019 8:33 pm

Careful testing required!
Heater wrote:
Sat Mar 23, 2019 7:20 am
According to wikipedia Ethyle oxide is often used for sterilization of electronics:

"Ethylene oxide is one of the most commonly used sterilization methods in the healthcare industry because of its non-damaging effects for delicate instruments and devices that require sterilization, and for its wide range of material compatibility.[100] It is used for instruments that cannot tolerate heat, moisture or abrasive chemicals, such as electronics, optical equipment, paper, rubber and plastics"

Not that it would not be wise to test for adverse effects.

Just autoclave it. Pi can take 120C for twenty minutes :)
Wikipedia's comments on ethylene oxide are simply wrong in some clinical regards:

Code: Select all

As a toxic gas that leaves no residue on items it contacts, 
Many items, famously plastic endotracheal tubes, must be rigorously out-gassed to render them safe to use. The gas penetrates and permeates the materials. They are correct in stating:
"... ethylene oxide itself is a very hazardous substance. At room temperature it is a flammable, carcinogenic, mutagenic, irritating, and anaesthetic gas.
Ethylene oxide is one of several tools in the medical trade for killing bugs but must be used with great care for patient and handlers alike.

Endoscopic equipment as used in colonoscopy and other "minimally invasive" medical procedures contain conventional and fiber optic parts that cannot tolerate ethylene oxide or require such prolonged out-gassing periods as to make them unusable. Inadequate out-gassing leads to tissue irritation and damage. While the RPi may or may not tolerate it, it would be crazy not to test rigorously.

By the way, autoclaving combines heat and live steam. The penetration and release of energy from steam adds greatly to the heat effects. Testing would be essential.

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pi-anazazi
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Re: Sterilization of Pi

Mon Mar 25, 2019 8:52 am

...but there is dry-heat sterilization also

https://en.wikipedia.org/wiki/Dry_heat_sterilization

Miles OT in the meantime.

If they want to use ethylene oxide or chlorine dioxide the question the TO asked was: Is there a risk for electronic discharging? Answer: no, 10 sec after powering off (by jdb » Fri Mar 22, 2019 4:23 pm)

The remaining posts (including my) are not helpful at all. People having equipment for ethylene oxide sterilization typically know what they are doing... ;-)
Kind regards

anazazi

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bensimmo
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Re: Sterilization of Pi

Mon Mar 25, 2019 9:31 am

Heater wrote:
Sat Mar 23, 2019 7:20 am
...
Not that it would not be wise to test for adverse effects.

Just autoclave it. Pi can take 120C for twenty minutes :)
I'll just get the pressure cooker out and test it ... Just need to wait for the Raspberries to grow and I can make some jam at the same time.

W. H. Heydt
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Re: Sterilization of Pi

Mon Mar 25, 2019 3:26 pm

I note that the OP has no other posts besides the one starting this thread.

Heater
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Re: Sterilization of Pi

Mon Mar 25, 2019 3:35 pm

Yep, I was beginning to get suspicious.

First poster, off the wall question, has not been back to join in the conversation since Friday.

Another wind up.

W. H. Heydt
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Re: Sterilization of Pi

Mon Mar 25, 2019 5:55 pm

Heater wrote:
Mon Mar 25, 2019 3:35 pm
Yep, I was beginning to get suspicious.

First poster, off the wall question, has not been back to join in the conversation since Friday.

Another wind up.
I'll give him credit for one thing, though. The question is, so far as I know, unique in these forums.

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bensimmo
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Re: Sterilization of Pi

Mon Mar 25, 2019 8:08 pm

There is a Mario Mata, work up in a Scottish Uni on tech based devices

hippy
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Re: Sterilization of Pi

Tue Mar 26, 2019 10:34 am

bensimmo wrote:
Mon Mar 25, 2019 8:08 pm
There is a Mario Mata, work up in a Scottish Uni on tech based devices
And others of the same name working in bio-engineering and medical fields.

But sure, having not come back to the forum over the weekend, the OP must be some sort of troll or wind-up merchant :roll:

Some people seem overly quick to start casting aspersions on others, with others always eager to jump on those bandwagons.

"Be good to each other".

pcmanbob
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Re: Sterilization of Pi

Tue Mar 26, 2019 2:52 pm

It may just be the case that the OP does not know that anyone has replied to their post,
I have seen comments before from new users saying they expected to get an email from the forum telling them someone had replied to their question, having not had an email they did not bother visiting the forum for some time.

Just because many of use visit the forum on a daily, hourly or minute by minute bases does not mean everyone will.
We want information… information… information........................no information no help
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Will5455
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Re: Sterilization of Pi

Tue Mar 26, 2019 6:22 pm

Troll or not this information although only in specific uses could be invaluable.
I do strange things and am sometimes the techhead stereotype.
deal with it!

W. H. Heydt
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Re: Sterilization of Pi

Tue Mar 26, 2019 6:48 pm

Will5455 wrote:
Tue Mar 26, 2019 6:22 pm
Troll or not this information although only in specific uses could be invaluable.
While true--and interesting--unless someone tries it and reports back here just raising the question doesn't get anywhere.

Heater
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Re: Sterilization of Pi

Tue Mar 26, 2019 8:59 pm

Will5455,
...this information although only in specific uses could be invaluable.
What information?

I perhaps learned more about sterilizing endoscopes than I ever wanted to.

I don't have any ethylene oxide or an autoclave around so sadly I can't report on how a Pi responds to such treatment.

Where is mario?

wh7qq
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Re: Sterilization of Pi

Wed Mar 27, 2019 12:47 am

Heater wrote:
Tue Mar 26, 2019 8:59 pm

I perhaps learned more about sterilizing endoscopes than I ever wanted to.
Please...not "sterilizing" but "disinfecting". Sterilizing means NO viable bugs. Disinfecting means "few", but not the same as "Sterile".
pi-anazazi wrote: ...but there is dry-heat sterilization also

https://en.wikipedia.org/wiki/Dry_heat_sterilization

Miles OT in the meantime.

If they want to use ethylene oxide or chlorine dioxide the question the TO asked was: Is there a risk for electronic discharging? Answer: no, 10 sec after powering off (by jdb » Fri Mar 22, 2019 4:23 pm)

The remaining posts (including my) are not helpful at all. People having equipment for ethylene oxide sterilization typically know what they are doing... ;-)


I would hesitate to subject most electronics to 170 C.

The people in hospitals and industry that know anything about ethylene oxide sterilization are often not the same ones that perform it...usually a much lower pay scale. Same for "disinfecting" endoscopy equipment. In some cases, they are very informed and conscientious but in other cases..."hurry up, it's near time for happy hour"

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