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What is the best humidity level for an electronic shop? On one end of the scale, you will have problems from corrosion due to high humidity and condensation, but at the other end there will be serious problems from ESD.

I've worked in shops at either extreme end of the scale, and would imagine the ideal level being around 50% relative humidity. Thoughts?

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Just working with grounded wrist-straps, and keeping major ESD generating clutter to a minimum, you shouldn't have much problem down to about 40% relative humidity. However, below 35% or 40%, you should start being extra vigilant.

For example, it's always a good idea to keep styrofoam packing material, wool sweaters, polyester fleeces, and rolls of packing tape away from your ESD-safe work area, but when the humidity is very low, even ordinary paper can start to be a problem. An ordinary laminated surface that might be passable at high humidity can start to cause problems when the air gets very dry. The professionals use grounded mats on the workbench surface all the time. When the air is very dry, ionizing fans become necessary.

So, you can work with almost any R.H., depending on the level of protection measures you have in place.

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  • \$\begingroup\$ That certainly lines up with what I've seen in the past. In one shop I worked at in southern Arizona, the humidity was so low you would get powerful electrostatic shocks just walking 5 feet. Wrist straps and mats were an absolute must! \$\endgroup\$ – Jesse Jul 15 '10 at 15:07
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    \$\begingroup\$ We were always supposed to wear cotton in the lab. Fleece was prohibited. \$\endgroup\$ – AdamShiemke Jul 15 '10 at 15:36
  • \$\begingroup\$ Being in the Army, we were required to wear highly starched Battle Dress Uniforms (BDUs.) Their ESD characteristics left MUCH to be desired. \$\endgroup\$ – Jesse Jul 15 '10 at 15:48
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    \$\begingroup\$ The fleece problem happens when you have separate hardware and software departments, and a representative of the latter has to be invited to the lab when verification testing gets interesting. \$\endgroup\$ – JustJeff Jul 15 '10 at 16:43
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There are also ergonomic factors, human beings work best at 40% to 60% RH.

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50% seems a bit low. Corrosion of metallic parts has never been an issue in my experience, and condensation is usually not an issue in a climate-controlled building unless you bring metallic parts in from the cold in winter.

I'd probably shoot for something in the 70% range to be safe.

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  • \$\begingroup\$ I personally don't enjoy above 60% (see @Leon Heller's answer) but I also don't want to have problems from handling-related ESD. I suppose the best way to mitigate handling exposure is ESD bags, though... \$\endgroup\$ – Jesse Jul 15 '10 at 15:52
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    \$\begingroup\$ You need ESD Bags. You need ESD straps, and you have to check each component to make sure they are not sensitive to humidity(this can happen quite commonly) \$\endgroup\$ – Kortuk Jul 15 '10 at 18:32

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