Electrostatic discharge (ESD) mats are essential in workplaces where equipment could be damaged by static electricity buildups and releases. ESD table mats and floor mats both help, but you should also look into additional ways to get rid of static electricity just so that the mats don't let even a tiny bit through. You can do so rather easily, though you'll need the cooperation of employees, and you'll have to play around with the environmental conditions in the room.
Increase Humidity in the Work Area
If the humidity in the room is less than 40 percent, static electricity is more likely to build up. You can increase the humidity a bit without suddenly making most equipment corrode (you do want to keep the humidity under 80 percent, though, both because that level of humidity promotes corrosion and because it is really uncomfortable for humans). You may have to play around with the humidity a bit because air conditioner use reduces humidity. Add a room humidifier and see if you can get the ambient level, along with adjusting the air conditioner, to over 40 percent.
Have Employees Discharge Extra Static Electricity Before Entering
Static buildup can happen anywhere, at any time, though dry days are more likely to promote static electricity buildup than wet days. People who drove to work, too, may have extra static buildup after getting out of their cars. Have people grab a part of the metal portion of their car doors as they get out so that they do not continue to carry the charge with them (and so that they don't shock themselves if they touch metal afterward). Also have them touch something made of metal, like a doorknob, before they enter the room with the sensitive equipment.
Ban Certain Clothing Fiber Types
Everyone has had to peel freshly laundered clothing apart because of all the static electricity that made items cling together. It is possible for any type of clothing material to create static electricity if it rubs against something else, but synthetic material and wool seem to generate a lot more static electricity than other materials. For equipment that is particularly sensitive to static electricity, have employees working with that equipment avoid synthetic or wool clothing. Ask them to stick to cotton if possible.
Remember, ESD mats are still necessary when you're working with really sensitive equipment. They provide at least a basic defense against static buildup, so double-check that all workstations have them before anything else.