ESD mats

[likephysics]

I don't understand how exactly ESD mats work. They prevent build up of Electrostatic charge. So any non-wool material would qualify as an ESD mat?
Do ESD mats also help discharge an already build up ESD, like a person clothed in sweater and charged up to couple of Kilovolts?

[berkeman]

I don't understand how exactly ESD mats work. They prevent build up of Electrostatic charge. So any non-wool material would qualify as an ESD mat?
Do ESD mats also help discharge an already build up ESD, like a person clothed in sweater and charged up to couple of Kilovolts?

ESD mats are grounded to bleed off static charge. They are made of mildly conductive material, say a few 100k Ohms per square, and often have an explicit resistor in the connection to Earth ground. The explicit resistor is to cause the bleed-off to be gradual, instead of sudden like with an ESD shock.