Guessing the office space has a concrete slab, I would recommend for your situation not to install a floor material at all, but acid etch the concrete and apply a fish oil concrete stain to it.
This is easy to maintain, and will allow for cleanup from your crews dirty boots.
For more information:
Read "Is recycled rubber flooring a green and healthy choice? We're considering it for a basement living space." a Q&A answered by Cynthia Phakos.