ANSI/ESD S20.20 doesn’t mention hair, but the ESD Handbook ESD TR20.20 does. The general rule from ANSI/ESD S20.20 is in section 8.3.
From ESD Handbook ESD TR20.20 mentions “human hair” is near the extreme end of the Triboelectric Series, so it can be high charging. But the above rule would apply; keep hair 12” away from ESD sensitive items. ANSI/ESD S20.20 says:
“In order to mitigate field-induced CDM [Charged Device Model] damage, the ESD program shall include a plan for the handling of process-required insulators. If the field exceeds 2,000 volts/inch, steps shall be taken to either:
A) Separate the insulator from the ESD-sensitive device by a distance of 30 cm (12 inches);
B) Use ionization or other charge mitigating techniques to neutralize the charge.”
If the person is grounded, will the charge on the hair be removed to ground? No. An insulator, hair being a non-conductor, cannot be grounded. The charge on a person’s hair would remain being slowly neutralized by natural ions in the air.
The hair question is similar to clothing which is almost always insulative. The clothing cannot be grounded. We say that the charge stays on the person’s clothing, but if covered by a Statshield ESD Smock that like a Faraday Cage, the fabric shields the charges from the ESD sensitive items. Technically, with the conductive fibers in the fabric, the charge is attenuated.
The technical information on dissipative hats would be would be similar to ESD smocks. “Garments are intended to attenuate electrostatic fields that may be present on personnel clothing. … While a person may be grounded using a wrist strap or other grounding methods, that does not mean that insulative clothing fabrics can dissipate a charge to that person’s skin and then to ground. Personnel clothing usually is electrically separate or isolated from the body.” [ESD TR20.20 section 220.127.116.11]
Regarding contamination, the handbook includes “Skin flakes, hair, biological pathogens and other human contamination continues to be the source of many contamination problems. Industry has recognized this problem and taken steps to protect contamination sensitive products from being adulterated by human hands and fingers.” [ESD Handbook ESD TR20.20 ESD Glove section 18.104.22.168 Introduction]