The requirement is based on partcle count...not how you achieve it.
Some things to note:
- There are various requirements for different particle sizes. Many customers only care about 0.5um and up...but some care about the whole spread. Check out the requirements for 0.1um, 0.2um also...
- Gowning and dress is simply a tool, as are airflow, bioburden (love that term...I'm a Bioburden!...I always thought I was just plain human), # of inlets, location of returns, inlet & return balancing, local process particulate capture, etc.
Use the tools to achieve the particle count requirement...
Make sure to measure the particle count with people actively working in the room, otherwise you just have a meaningless number.
Note also that dress is a multifaceted tool...it can affect employee attitude and expected behavior as well. A minor point to be sure, but get the mileage where you can.
Note lastly that appearance affects not only your employees, but your customer's impression as well. Show me a dingy looking cleanroom with an acceptable particle count, I'll consider having it measured myself or shopping elsewhere.
While you are upgrading the cleanroom, keep your eyes open for the additional low hanging fruit