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Static Electricity

10/31/2012 11:35 AM

Hi, I hope one of you enlighten me.

We use an exhaust hood to deliver some aerosolized medications to patients via compressed O2 powered nebulizers. These devices are all made of plastic. The medication is a liquid. We have had some rare occassions of patients reporting shocks and/or blue sparks during this treament. We contacted the hood manufacturer and the nebulizer manufacturer and they could offer no explanation.

Any thoughts on this? Why only a few patients? I appreciate your time!

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#1

Re: Static electricity

10/31/2012 11:41 AM

What are you doing for "grounding"?

You might want to look into the subject of ESD (Electro-Static Discharge) and the mechanisms used to control it.

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#2
In reply to #1

Re: Static electricity

10/31/2012 11:47 AM

I think all we have is the 3 prong plug which goes into a plug marked "grounding plug only" socket. (keep in mind I have sub minimal electricity knowledge)

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#3

Re: Static electricity

10/31/2012 11:50 AM

What sort of liquid, i.e. is it electrically conductive, an aqueous solution, perhaps?

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#5
In reply to #3

Re: Static electricity

10/31/2012 12:05 PM

It is a powdered medication called pentamidine and it is mixed with 0.9% sodium chloride

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#36
In reply to #5

Re: Static electricity

11/03/2012 9:16 AM

That concentration of saline is very conductive of electricity and a saline mist (regardless of what else is mixed in with it) will render wetable surfaces electrically conductive. Why are you sure it is static buildup? Could it be that the shock is due to current conducted via a saline-wetted surface through the patient to ground, or vice versa? Is it a single jolt only or a continuous shock? If continuous it is NOT static buildup and potentially deadly. (!!!)

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#4

Re: Static electricity

10/31/2012 11:58 AM

You may what to call EXAIR.

They do make static eliminators for sheet plastic. I didn't look through it, but they may also have something for your application.

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#6
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Re: Static electricity

10/31/2012 12:06 PM

Thanks for your input!

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#7

Re: Static Electricity

10/31/2012 12:14 PM

This is not unlike what happens when you slide across your seat in the wintertime and get shocked.

When two non-conductive surfaces, or particles in this case, come into contact and then have that contact broken, a static charge is generated. The patient's lips, being conductive, then bleed the charge directly into the patient.

Simply having the patient hold the device for a few moments prior to use might bring both the inhaler and patient to the same electrical potential.

Static eliminators contain a small amount of radioactive material. That may have implications in a hospital.

If possible, increasing the humidity in the room may solve this problem, too.

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#8
In reply to #7

Re: Static Electricity

10/31/2012 12:47 PM

Thanks so much. Our Biomed guy is coming up to check the grounding. It's strange (to me) that this only happens on a very few patients. I really appreciate the fast, informative responses from this forum! You all are great!

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#9
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Re: Static Electricity

10/31/2012 1:04 PM

It's strange (to me) that this only happens on a very few patients.

Is that the same patients repeatedly, or, is it just random: for example does it only happen when air humidity is low?

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#10
In reply to #9

Re: Static Electricity

10/31/2012 1:24 PM

Specific patients--same repeatedly. How weird is that? And we are in a climate controlled area, treatment is done monthly, and it happens every time. This one patient even had it happen at another facility.

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#11
In reply to #10

Re: Static Electricity

10/31/2012 1:42 PM

Not joking here.

What sorts of material are their clothes made from?

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#13
In reply to #11

Re: Static Electricity

10/31/2012 2:14 PM

Jeans and a flannel shirt. Can't remember the shoes...

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#15
In reply to #13

Re: Static Electricity

10/31/2012 2:37 PM

See ozzb's post at #12 below (GA BTW).

Are they seated or standing when the procedure takes place?

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#16
In reply to #15

Re: Static Electricity

10/31/2012 3:01 PM

Seated on a plastic chairs with metal legs.

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#17
In reply to #16

Re: Static Electricity

10/31/2012 3:24 PM

On shag carpet in the dead of winter? :)

Like I said before, reading up on ESD and the methods to mitigate it will help.

However, you probably need to hire or contract someone who is an expert in the field since this is a public health situation. There are lawyers everywhere and if it was found you were relying on ad-hoc methods to solve a problem it could backfire legally.

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#19
In reply to #17

Re: Static Electricity

10/31/2012 3:31 PM

On linoleum. We are having it all checked out and documented correctly. We were just perplexed that it was only a couple patients on multiple occasions. We are very "by the book" here--safety is our highest priority. I figured a bunch of engineers would have some good input and was I right! I basically got similar answers as the one our Biomed guy gave us--he is awesome. I thank you all for your input. You have made my day!

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#20
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Re: Static Electricity

10/31/2012 3:35 PM

Clothing worn by the patient may be the factor you are not controlling.

ESD mats and grounding stations may be the right way to deal with it. If the patient is made ESD neutral the chance is that you will not have the problem.

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#18
In reply to #16

Re: Static Electricity

10/31/2012 3:26 PM

Can you try an all metal or wooden chair?

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#21
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Re: Static Electricity

10/31/2012 3:37 PM

Wood will isolate the patient. Metal would bleed the ESD away, but perhaps too rapidly.

I am thinking they will need an ESD mat on the floor or ESD tiles and some sort of grounding station that the patient would grab or touch as part of the process to bleed off ESD in a slow and controlled way (so as to not feel a shock).

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#37
In reply to #21

Re: Static Electricity

11/08/2012 10:31 PM

yes, that would work. but we are talking about a clinic/hospital environment, they are going to wax the floor and that will ruin the ESD mat or tiles. I do think different chairs would help along with an ESD wrist strap provided it is used properly.

still thinking they may be having an issue with the delivery system. Are they using more than one nebulizer? can they track them to see which one(s) is/are causing the issue.

the responder who stated it could be the individual is also on a great track. I know I can't sit too close to an FM radio or the signal goes bad. Haven't heard if there is a way to test the capacitance of a person?

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#22
In reply to #10

Re: Static Electricity

11/01/2012 12:47 AM

Each human has a different capacitance. If it is the same people, have them try a wrist type ground strap.

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#12

Re: Static Electricity

10/31/2012 2:09 PM

Though the solids in this device are most likely producing some charge. The rate of charge would depend on how fast. If they where moving that fast I would think the the procedure would be very uncomfortable to the patient.

I would look at each patient. The static may be in them. Look at their foot wear. Wool slippers would create static. Also how they walk do they shuffle their feet dragging them on the ground. The material of the clothes these few people wear. Do these people have dry skin. Dry skin can offer the highest resistance to current. Until you get it wet.

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#14
In reply to #12

Re: Static Electricity

10/31/2012 2:16 PM

check the humidity, maybe consider putting in a humidifier.

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#23
In reply to #12

Re: Static Electricity

11/01/2012 1:00 AM

When I was in training for fuel handling equipment we were shown videos (old ones) of dry air flowing through pipes. The voice-over described how microscopic dust particles in the dry fluid (air) can generate static charge in the pipe. They used this principal to detonate balloons filled with flameable gasses.

Your dry powder increases the contact between the particles and the pipe generating the charge. As others have said there are many properties that govern any person's electrostatic potential; clothing, body composition, humidity, shoes etc.

Look for a way of making your equipment conductive either through a surface coating or through plastic composition. Have the patient wear a static discharge bracelet and equalize the potential between them and the equipment and you should eliminate the chance of a spark when they contact the equipment. The bracelets will discharge any potential at the wrist where there are fewer nerve endings to feel any shock as it is equalized over a larger surface area.

Drew K

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#24

Re: Static Electricity

11/01/2012 2:10 AM

Anybody wearing sweaters or using blankets?

Take a look at surrounding materials such as sweaters, or plastic bed liners, blankets, socks, hair etc. and technique.

Any sort of plastic to plastic can result in static charges.

Pulling a plastic mask over a blanket might actually be sufficient. The sheet would provide an insulator, so the patient is not touching the blanket. This COULD provide a shock.

Just a thought.

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#25

Re: Static Electricity

11/01/2012 6:33 AM

Lots of good suggestions given by others. Just in case you "don't see the light" I'll summarize in simplistic terms.

1) Low humidity tends to cause ESD (Electro Static Discharge) problems. Higher humidity might reduce buildup of charge. Due to humidity ESD tends to be worse in the winter.

2) ESD problems are the build up of static charges and then the RAPID discharge of the static charge. The "ESD wrist strap" suggestion by others would cause a slow and constant discharge of ESD. ESD wrist straps are common in electronics assembly and repair facilities.

3) Some materials generate static charge when rubbed together. Remember first grade science where the teacher ripped paper into small pieces and used a hair comb to pick up the paper? Any material combinations that act like "rubber and wool" or "silk and glass" from first grade will tend to cause more static charge build up. Thus, cotton clothing will tend to cause less buildup of charge and synthetics, silk and fuzzy sweaters will tend to cause more buildup of static charge.

4) Grounding equipment or causing plastic surfaces to be conductive might cause all static to quickly flow (before buildup, not a large discharge) to ground but you might be very limited to what you could try from both a practical point of view and a liability point of view.

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#27
In reply to #25

Re: Static Electricity

11/01/2012 9:12 AM

I remember a story in one of our ESD classes where a company had a bank of computers in a room that would spontaneously reset and the operators were not able to track down the source of the problem.

An outside consultant had a theory, so he donned a pair of polyester pants (the same pants that many of the executives were wearing), walked into the computer room, then put his hand in the pocket and toyed with a bunch of coins - Bang - instant reset of the computers.

That was the end of polyester suits. :)

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#28
In reply to #27

Re: Static Electricity

11/01/2012 9:34 AM

cool, I never like the 70's anyway......... except some of the bands, rock bands that is.......

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#29
In reply to #27

Re: Static Electricity

11/01/2012 9:43 AM

One of the primary requirements of explosives handling is that you MUST be dressed in cotton clothing. No synthetics allowed.

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#32
In reply to #29

Re: Static Electricity

11/01/2012 12:51 PM

It is the same in the fuel industry, but for other reasons also. If you are caught in a fire cotton and other natural fibers will burn slowly and protect you instead of melting to your skin and making it worse.

Drew K

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#33
In reply to #32

Re: Static Electricity

11/01/2012 12:58 PM

Ask any welder clothing of choice, other than leathers

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#34
In reply to #32

Re: Static Electricity

11/01/2012 1:10 PM

Same with flying, or it was when I learned.

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#35
In reply to #34

Re: Static Electricity

11/01/2012 7:33 PM

All the Pilots I knew wore nomex suits. They had started issuing nomex coveralls when I got out. I still have a flight suit and some flight gloves!

When I worked on the pipeline, we were issued nomex coveralls to wear on certain jobs but everyday clothing had to be cotton or specifically flame retardent.

Now the electricians I work with wear certain calorie coveralls for working with different voltage breakers, not sure if they offered different levels of nomex fire resistant clothing.

Drew K

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#31
In reply to #25

Re: Static Electricity

11/01/2012 10:08 AM

5) You must be responsible for safety and legal issues if you read this comment. When it is difficult to figure out how to make something better then sometimes it is useful to figure out how to make it worse. Then, you have a better understanding of what it is that you don't want to do. If you can safely and legally do it consider testing the equipment in a walk-in freezer with a person wearing synthetic clothing and a fuzzy sweater on a plastic chair on top of a shag carpet rug. If you notice the problem being worse then you can change things one at a time and learn something. Remember, I said "might" and "maybe". Also, safety and legality are your responsibility.

6) The hood manufacturer and nebulizer manufacturer might not have much of an interest in calls about an annoyance of shocks or sparks. Chances are your response would be better with a call of concern about the safety of patients with pacemakers or other health compromising conditions.

7) It is always good for your career to remember that a common technique for management to clear their desk of problems is to shoot the messenger.

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#26

Re: Static Electricity

11/01/2012 8:58 AM

The fact that you are breaking a liquid into an aerosol will generate static electricity; similar to unwinding scotch tape in a dry environment. This means that anything the spray hits will become charged, unless it is grounded There are many methods to mitigate the effects of the static electricity, but the most direct method is to use an ionizing loop at the aerosol exit.

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#30

Re: Static Electricity

11/01/2012 10:08 AM

Placing the order today for a mat and a wrist cord. I have learned so much from you all. Now, get back to work!!!

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#38

Re: Static Electricity

11/13/2012 7:10 PM

Are men or women more prevalent? Panty hose coupled with polyester, slips/skirts/slacks are bad combinations. Antistatic flooring as found in computer centers and communications centers may be offer a solution. Try spraying the floor and chair with one of the consumer static guard concoctions used for clothes. As everything seems to be plastic, grounding will probably be ineffective. You don't want a "hard" ground to the patient as that will just increase the severity of the shock. It is hard to tell at this point if the patient or the equipment has the higher potential. To ground the patient, you could try one of those wrist grounding straps technicians use.

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#39
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Re: Static Electricity

11/13/2012 7:34 PM

If you can't find an anti static spray, mix an anti static fabric softener with water and use that

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