Suck = static, blow = safe?

[Nimby]

There are loads of claims on the web that you should never use a vacuum cleaner to suck dust out of your PC "because of static", and that you should use a can of compressed air to blow it out instead.

Now apart from the fact that all the socketed / surface-mounted chips are grounded and probably safe from static anyway, why would sucking cause static but blowing not? Moving air is moving air after all.

Has anyone ever checked with an electroscope (remember that from O-level physics?) if you get static from a vacuum cleaner nozzle but not from a can of compressed air?

[ruggedscotty]

Static is a major killer of integrated chips.

Any air flow will create static due to the action of the molecules in the air moving and the charge that can generate through friction. The can of air ? its compressed filtered gas that is particulate free. A vacuum or a compressed air line that isnt filtered very well have particulates that can generate static.

https://incompliancemag.com/article/how-is-static-...

[Nimby]

But you're still moving the dust in the computer at high speed even if you blow it with filtered air from a can.

Bring back Mythbusters...

[Mr Pointy]

The static is generated by the passing of rapidly moving air over the cleaner nozzle; you can buy anti-static vacuum cleaners which have hoses & nozzles made from conductive plastic. You can buy static safe air blowers as well.

I'm not sure why you think the "chips are grounded": they most certainly aren't.

You should also not allow the airstream to rotate any fans blades as they can overspeed & generate high back EMFs which can damage to driver chips.

[ruggedscotty]

Nimby said:

But you're still moving the dust in the computer at high speed even if you blow it with filtered air from a can.

Bring back Mythbusters...

its the dust in proximity, in a large area the dust separates, check out venturi effect.... vacuum dust is sucked into a nozel which concentrates the effect, blowing from a can the dust spreads so the effect is much much less.

[Beati Dogu]

I was told once not to use a vac because it would spin up the cooling fan, generating a current, which may cause problems.

While my first instinct is to call BS, it is at least borderline plausible I suppose.

[Nimby]

Mr Pointy said:

I'm not sure why you think the "chips are grounded": they most certainly aren't.

Hmmm. I'm assuming 0v pin(s) on components to motherboard ground plane, ground plane to PSU ground, PSU ground to case and earth (assuming power lead plugged in to wall socket). Isn't that the path of least resistance any static charge would take?
My meter reports continuity between a USB socket's 0v and the mains plug's earth pin - haven't been inside to probe actual ICs.

[2fast748]

Using a vacuum cleaner can potentially loosen components on circuit boards but using compressed air from a can can freeze components as well so whatever you do can cause damage!

[Mr Pointy]

Nimby said:

Hmmm. I'm assuming 0v pin(s) on components to motherboard ground plane, ground plane to PSU ground, PSU ground to case and earth (assuming power lead plugged in to wall socket). Isn't that the path of least resistance any static charge would take?
My meter reports continuity between a USB socket's 0v and the mains plug's earth pin - haven't been inside to probe actual ICs.

Yes, on your USB example the 0v lines MAY be at mains earth potential but the +5v & data lines aren't - try putting your meter across them. Now put 20kV on the same pins & see if they work afterwards; that's what static does.

[Mr Pointy]

Beati Dogu said:

I was told once not to use a vac because it would spin up the cooling fan, generating a current, which may cause problems.

While my first instinct is to call BS, it is at least borderline plausible I suppose.

No, it's true. It's very easy to spin the fan incredibly quickly & when you do this the fan motor is generating a voltage back into the driver circuit (generators & motors are much the same thing). While the driver circuitry may have back-EMF protection it has a limit to the voltage it can withstand.

[Nimby]

Mr Pointy said:

Yes, on your USB example the 0v lines MAY be at mains earth potential but the +5v & data lines aren't - try putting your meter across them. Now put 20kV on the same pins & see if they work afterwards; that's what static does.

You asked why I thought in-circuit IC's were grounded and I explained. Obviously not every pin is connected to earth - is that how you would define it?

[Mr Pointy]

Nimby said:

Mr Pointy said:

Yes, on your USB example the 0v lines MAY be at mains earth potential but the +5v & data lines aren't - try putting your meter across them. Now put 20kV on the same pins & see if they work afterwards; that's what static does.

You asked why I thought in-circuit IC's were grounded and I explained. Obviously not every pin is connected to earth - is that how you would define it?

Well I don't see why you would think that the fact that one pin is grounded going to save a chip from static damage? What about all the other pins?

[Nimby]

Mr Pointy said:

Well I don't see why you would think that the fact that one pin is grounded going to save a chip from static damage? What about all the other pins?

The same way lightning conductors work; you only need one point grounded to provide the easiest path.

[Toltec]

Mr Pointy said:

The static is generated by the passing of rapidly moving air over the cleaner nozzle; you can buy anti-static vacuum cleaners which have hoses & nozzles made from conductive plastic. You can buy static safe air blowers as well.

I'm not sure why you think the "chips are grounded": they most certainly aren't.

You should also not allow the airstream to rotate any fans blades as they can overspeed & generate high back EMFs which can damage to driver chips.

Pretty much this ^

The nozzle of the vacuum will tend to build charge and the damage is done if you earth it through a component, air and dust could potentially build a charge on those components, however if their 0V pins are grounded the circuit leakage from the other pins will prevent a charge from building up. Anti-static wrist straps have a resistance in the megaohm region, this provides sufficient grounding to prevent a buildup of charge, while at the same time preventing a current flow that could cause electrocution if you accidentally touch a live component.

If you are using a can of anti-static spray then you still need to wear an antistatic wrist band to prevent static build up on the can.

Sprays can easily overspeed a fan too, just stick a tywrap or similar plastic object through the fan before cleaning it to stop it spinning.

[ruggedscotty]

spinning up a fan with compressed air damage the driver ?

https://arstechnica.com/civis/viewtopic.php?t=1209...


https://www.cnet.com/forums/discussions/compressed...

[mikef]

I use a Datavac Pro and for good measure a rechargeable Hurricane blower

I have also tended to worry that canned air might be too powerful for delicate connectors and fans

Those and some keyboard putty gel are all you need to keep PCs like new. Well apart from re-installing Windows every few months (not needed on Macs)

[crofty1984]

2fast748 said:

Using a vacuum cleaner can potentially loosen components on circuit boards but using compressed air from a can can freeze components as well so whatever you do can cause damage!

I just chuck it in the bath.

[Halmyre]

I took my PC outside, removed the side panels and blew off the dust with my wife's hairdryer. Still working.