Is it necessary to wear ESD foot straps on both feet? Where is this defined in the standards?
Most standards do not explicitly tell you to wear foot straps on both feet. However in order to control the body voltage reliably and prevent ESD risk, the body must be continuously grounded and the resistance from the body to ground must not be greater than 35 Mohm.
If you wear only one footstrap, your body is not grounded when that strap loses contact with the floor and the body voltage can quickly rise to hundreds of volts, giving ESD risk. So, it is not good practice to wear only one footstrap.
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In our electronics instrumentation manufacturing facility, we require all of our operators that work full-time IN the manufacturing area to wear foot grounders while there.
A frequent comment by many in our facility is that, although they enter an EPA, they do not touch ESDS components.
Is it necessary for all personnel who enter an EPA to wear foot grounders?
If your ESD prevention Program specifies that they need to wear grounders, then they need to.
In current standards IEC 61340-5-1:2007 and ESD S20:20:2007 personnel must be grounded if they are handling ESD susceptible parts. If they do not, then you are free to write in your ESD control program that they do not have to wear foot grounders or any other grounding devices. However You might consider whether it is wise to do so as it may cause considerable confusion if some people are allowed into the EPA not wearing grounders, and others are not. Also, can you guarantee that a person entering the EPA who is not wearing grounders, will never be tempted to (or without thinking about it) handle ESD sensitive parts? Specifying that everyone must wear grounders removes these confusions and risks.
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