I performed measurements on the ESD epoxy floor. The floor shows good resistance to ground and good point-to-point resistance. However, when performing the walking test, the voltages increase to above 200 volts.
We replaced the heel straps with new ones, but the problem persisted. It appears that the floor is not capable of dissipating the charge generated by the operator.
Do you have any suggestions on how to resolve this issue?
Alex,
This can happen often where a floor doesn’t work well with some types of footwear.
First thing I suggest is cleaning the floor, if you haven’t done that already. If this works you may need to clean it more often to make sure it performs as needed.
Next, I suggest trying a different heel strap or going to a full foot grounder instead of a heel strap. The foot grounder makes more contact with the floor. They take a little longer to put on but they are about as inexpensive as heel straps.
After that you could try waxing the floor, this may give better results. If it works, it means you may need to repeat this every few months to ensure the floor performs as needed.
The last suggestion is trying ESD shoes. This is a more expensive option but there are less expensive options out there that may suit your needs. Perhaps one will pass with your floor.
Thanks.
Greetings of the day from India to all the members on the forum and welcome back to Mr. Alex after a long gap 
First of all an ESD floor is not qualified fully as an ESD safe floor for use in an EPA without qualifying it with proper compatible ESD foot wear and the personnel to clear the requirement of System Resistance and the walking voltage .
It is mandatory to ensure that all the parameters are met for the Footwear - flooring Combination per ANSI ESD STM 7.1 /9.1/97.1 and 97.2
Remember ESD Control & Clean room concept are complementary to each other .
In my opinion , Negative points on the usage of Heel straps are;
1.While the heel straps and toe straps are still in use in parts of the globe , it is practically not advised in the current trend of electronics technology advancing across the globe as even the smallest micron dust from the sole of the private footwear may lead to static generation and could affect the process inside a clean room environment thereby defeating the purpose of your heel strap usage .
While walking with heel straps worn on your private footwear to avoid changing over of the footwear, as per point 1 above it does carry in the outside dust particles inside your EPA and thus instead of entering an EPA with fool proof EPEs with less than 100v body voltage, you will rather carry inside more than that through your foot soles.
At times the conductive strip or the conductive knee band connected your leg and the heel strap covering the heel of your private footwear may not be effective to develop required contact with the human body which leads to failure of your heel straps .
Further, more important factor is that, at times while walking, your heels or one of the heels may not be in full contact with your ESD safe floor but remain in air and might be generating high voltage due to larger surface of the bottom of front portion of your private footwear in contact with the floor.
Thus ; my sincere suggestion is to start using exclusive ESD safe footwear and confirm that the system comply with all the four test methods referred above .
ESD footwear will serve as a clean room cum ESD safe footwear . Remember to restrict the usage of the ESD safe cum clean room footwear to be used only in the EPA always. It is not a good practice to keep moving with this special footwear to wash room -pantry - reception bay etc . .
Prevention is Better Than Cure - Need to Develop the Culture -Practice Makes a Man Perfect
ESD Control is an Insurance cover to your sensitive ESSDs.
Protect them - Increase their reliability
Create Personnel Awareness with proper training- Conduct regular compliance verification audits
Ensure to have Detailed Product Qualification test reports on every new purchases of EPEs before putting them into use - Conduct regular process assessment checks
Just do not rest on only document based facility certification program.