The HEPA filtered enclosure is filtered with H13 or H14 or U15 filters and are incredibly versatile. They could be called walk in laminar flow booths or clean enclosures or perhaps cleanroom tents. They can be portable or fixed, they can be designed to provide a particle count over the process equivalent to any of those described in ISO 14644-1:2015.
They can be situated in a cleanroom if you need to increase the level over a particular area. E.g. In an ISO 7 cleanroom to cover has one part of the process that requires ISO 6 but they can also be situated directly in a ‘dirty’ process/assembly/ manufacturing environment to protect one particular piece of equipment or process.
The HEPA filtered clean enclosures are designed to be fully tested to the requirements of ISO 14644 part 1 and 3 and in accordance with the design requirements of part 4 but due to the soft walls and construction methods of the clean enclosure they will never achieve enough positive pressure to guard against the risk of particulate moving up stream and onto the process but for some projects this is not an issue.