Aside from assurances that the supplier’s stated specifications are being met, electrical resistance testing ensures that one’s garments stay within the parameters for ANSI/ESD S20.20-2007 compliance.
What determines compliance? Many end-users and suppliers of static control garments believe that measuring surface resistance <1.0 x 1011 ohms is the upper limit for acceptance even if the ESD garment is new. That may be acceptable for a disposable ESD garment, but after prolonged use, in combination with laundering, the fabric will lose conductivity over time.
ANSI/ESD STM2.1 requires that ESD garments being considered for qualification must be washed at least three times per the manufacturer’s defined cleaning process with a submission of three samples for qualification testing. However, many companies default to acceptance testing, thus allowing the end user to determine what humidity to test and what sample size to utilize.
Source: Static Control Garment Verification to Ensure Supplier Conformance