Static and airflow

[trimaster]

I'm told static can be generated by airflow, ie blowoffs. Can anyone verify this?

[brethin]

Re: Static and airflow

If the air is ionized air static is removed (proper blowoffs), normal air can and does generate static yes.

[ratdude747]

Re: Static and airflow

thread moved from FAQ.

[999999999]

Re: Static and airflow

Movement of dust can cause it, particularly if humidity is low and the airflow is high velocity (relative increase in static discharge rate).

What is the context for the question? I've cleaned things like motherboards with canned air and/or a paintbrush for years and the really nasty (whole computers) were sometimes so bad that I didn't even do that until I had cleaned them with a leaf blower at a few paces away. Never had a problem doing so, ESD issues seem more related to a person generating a static charge then touching an object before discharging themselves to same potential as the object (which isn't the same as what some do - earth grounding yourself doesn't necessarily put you at the same potential as the object unless it too was/is earth grounded).

[delaware74b]

Re: Static and airflow

^ x2 9's. I was using a shop-vac to clean bulkheads above storefronts in a local mall for lighting project. I about got knocked off the lift from the static buildup between the vac hose (plastic) and the nozzle attachment (also plastic). The charge was so high the arc could be seen.

[trimaster]

Re: Static and airflow

So the answer is yes. Airflow will generate static. Grounding required.

[PCBONEZ]

Re: Static and airflow

Oh heck yes!
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[999999999]

Re: Static and airflow

So the answer is yes. Airflow will generate static. Grounding required.

In the attempt to create a short summary statement you have also constructed a statement that is more often false than true.

A number of conditions must exist before merely having airflow will create a situation where there is sufficient static generation to require grounding. For example the PC you are typing on probably has one or more fans moving air but no grounding shield to divert the minute static charges created from doing so as the dust particles blow past component leads and traces. For example there are chip freeze sprays designed specifically to blow on ICs, contact cleaner solutions, dust cleaner sprays, etc.

The primary problem with the topic question is it was worded so vaguely that it there is no useful definitive answer unless we put it in the context of suggesting not to use a motorized high volume, high flow rate blower or vac in heavy dust areas, though arcing on a blower/suction nozzle or tube is an exceptional situation as the particles are traveling so far and fast against an insulating material that a charge builds up to a higher level than it otherwise would, BUT you usually aren't blowing dust out of a tube onto something so the dust did not reach high charge or retain that velocity at the point of contact with the circuits you'd be concerned about.

Lastly some circuits like CMOS are far more susceptible to ESD damage. Certainly if/when reasonably possible, grounding possibilities can be explored, but but in most "blowoff" situations, they aren't actually needed. Maybe it's better to suggest using the right tool for the job, an electronics duster has far lower flow volume and airspeed than a regular household vac/blower does.

[PCBONEZ]

Re: Static and airflow

No, actually it's always true.
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It's generating static regardless of it being enough static to hurt anything.
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At least it is if the fan blade and/or any ducting is made out of metal, plastic, wood or glass.
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[999999999]

Re: Static and airflow

The part that's more often false is the presumption that you need to do anything about the static "most" of the time, that it really depends on the situation whether it's important to grounding the blower and/or use of only a blower with metal porting so it can be grounded, or that it's of any significance to know there is low level static. Metal does not contribute to static charges though, rather it is not an insulator so at least it will charge itself and that with a possibility of ground shunting the charge if/when it is necessary.

However if we want to be overly general and thorough, we could say that any particle has the potential to have (an electrical) potential so even if you're not blowing or sucking anything, simply letting a dust particle fall from the sky and land on something may transfer a static charge.