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Question Does ANSI/ESD S20.20 specify how frequently to test ESD floors?
Answer Short answer:
No, each user should specify frequency of testing ESD floor in their ESD Control Plan Compliance Verification Plan section.

Longer answer:
Per S20.20 paragraph 6.1.3. Compliance Verification Plan “A Compliance Verification Plan shall be established to ensure the organization’s compliance with the requirements of the Plan. Formal audits or certifications shall be conducted in accordance with a Compliance Verification Plan that identifies the requirements to be verified, and the frequency at which those verifications must occur. Test equipment shall be selected to make measurements of appropriate properties of the technical requirements that are incorporated into the ESD program plan.”

S20.20 paragraph Compliance Verification Plan Guidance states “In addition to internal audits, external audits (Organization and supplier of ESDS items) should be performed to ensure compliance with planned requirements. Verifications should include routine checks of the Technical Requirements in the Plan. The frequency of verification checks should be based on the control item usage, its durability and associated risk of failure”

S20.20 has an accompanying ESD Handbook TR 20.20. It has a comprehensive list of questions, however, only general periodic testing frequency advice is offered. Under Floor: “Another consideration is the monitoring requirement to assure that the floor material is still functioning within specifications. The types of monitoring and type of equipment are considerations. In some cases, a simple electrical resistance test with a megohmmeter may suffice. In others, a static charge generation test may be required.”

Many users measure floors Quarterly using a Megohmmeter Test Kit in accordance with or some modification of ANSI-ESD S7.1 Floor Materials. S7.1 paragraph “Perform a minimum of five tests per contiguous floor surface material or a minimum of five tests per 5,000 square feet (464.5 m2) of floor material, whichever is greater. A minimum of three of the five tests should be conducted in those areas that are subject to wear or that have chemical or water spillage or that are visibly dirty.” Dirt is typically insulative and an ESD protected floor cannot fulfil its function if covered by insulative material. See ESD’s 41290 Surface Resistance Test Kit.

The minimum recommended technical requirement of ANSI/ESD S20.20 Table 1 for ESD Floor is less than 1 x 109 ohms. However, if used as the primary means of grounding personnel, the Flooring-Footwear System is to be less than 3.5 x 107 ohms per ESD STM 97.1 Resistance Measurement in Combination with a Person and/or less than 100 volts per ESD STM 97.2 Floor Materials and Footwear-Voltage Measurement in Combination with a Person.

These are systems tests that may be more meaningful that just testing the floor component. One could write this in your Compliance Verification Plan & measure RTG through person & ESD footwear & floor to electrical ground similar to the ESD STM 97.1 test using a Megohmmeter Test Kit. A person wearing ESD footwear standing on the ESD floor holds one 5# electrode on the palm of their hand to measure resistance.

Alternatively, the Flooring-Footwear System proper functioning could be verified approximating the electrostatic charge on a person wearing ESD footwear moving on ESD floor (measured in voltage) similar to the ESD STM 97.2 test using an Ionization Test Kit with HBM Fixture.

The idea being only measure the floor as a component if a high out of spec number is measured.
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