What is the recommended relative humidity that a room should be kept at for ESD purposes?

There are no hard and fast rules or specifications regarding humidity for control of static electricity in the current ESD Program Management Standards. Our standard ANSI/ESD S20.20 -2007 (available for free download from www.esda.org) does not specify a humidity range for applications. While it is pretty well understood that humidity plays a role in the ability to generate, store and dissipate static charge, it is also known to be unreliable as a control mechanism. Certainly, static charge generation is far worse at 10% RH than at 90% RH but significant levels can still be generated at 90+% RH.

Your ESD Control Program must be designed to work at the lowest practical level of humidity you can expect in your environment. The northern tier of US states have cold winters (heating up air dries it out and it is difficult and expensive to replace the moisture) and the interior of factories may see very low RH (measurements of <3% in MN inside a factory and technical “0” RH on the north slope of Alaska have been recorded). If you make a statement in your program about maintaining a certain level of humidity and you are an ISO factory or a military contractor, what are you going to do when the humidity drops below the stated level? Close the doors and send everyone home? This has occurred before with some military contractors that had an RH statement in their Procedures. It is best to avoid this costly error by not making a statement about RH control.

A well designed ESD Control Program and good materials will function correctly at very low RH. There are some different rules for pyrotechnics, ordnance and flammable atmospheres so if you are in any of those industries then RH control may be required. The statements above relate to electronics manufacturing industries.

A static dissipative labcoat, why?

Conventional poly/cotton blends used for regular clothing generate high levels of static charge, which may be discharged to products. In the electronics industry, electrostatic discharge (ESD), which increases significantly in low humidity, causes most of the destruction or damage to electronic components.

Everybody knows wrist straps and heel grounders aare used to ground the Human Body Model. However, these items do not do anything for the static generated by clothing. The static dissipative labcoat will make a shield around the clothing, therefore protecting the sensitive materials from static. An added advantage to this is it will also give your team a new image of professionalism.

A total ESD program includes the use of static dissipative garments, along with other static control devices, to form a first line of defence against product damage in the areas of assembly, packaging, repair and testing.