Lots of contract manufacturers say they have a "cleanroom".
At one end of the scale, this is actually just a room that is clean...
At the other end of the scale is a true Certified Cleanroom. We do our manufacturing in a true Certified Cleanroom. This requires on-going environmental monitoring and maintenance in concert with outside, independent certification.
Medical devices need to be commercialized using robust cleanroom manufacturing practices, so ask for a Certified Cleanroom and be sure to check the certification records for compliance.