In a controlled environment, temperature and humidity are part of the product

The standard's own definition says more than the class does

ISO 14644-1 defines a clean room as one where airborne particle concentration is controlled and which is constructed and used to minimize the introduction, generation and retention of particles — and in which other relevant parameters, such as temperature, humidity and pressure, are controlled as necessary.

That last clause is the part that becomes a building problem. In practice these rooms run in a fairly narrow envelope, commonly 18 to 22 °C and 30 to 60 percent relative humidity, though that is normal practice rather than a clause of the standard. Holding it is a job for the enclosure as much as the air handler.

Where static stops being a bench problem

In electronic assembly the humidity number is not about comfort. ANSI/ESD S20.20 requires a written control program, defined ESD Protected Areas, personnel grounding, ESD-safe work surfaces, ionization where needed, and a documented verification plan. Flooring is explicitly part of that control set, with resistance requirements of its own.

The 2021 revision ties qualification of on-site control items to the lowest relative humidity on the site, which moves humidity out of the process engineer's column and into the building's. A room that dries out seasonally is a room whose ESD program was qualified against a condition it no longer has.

Where electrostatic behavior matters to what is being built, the panel surface can be specified for it. That is a decision made with the process in mind, at the same time as the room, rather than added to it afterward.

The same envelope, a long way from food

Laser and water-jet cells. Electronic assembly. Specialty and laminated glass. Pharmaceutical, biotech and life-science space. Packaging lines and X-ray inspection. Robotics cells that have to sit at a set temperature to run repeatably.

What these have in common is not the industry. It is that an inconsistent environment shows up later as inconsistent product, and by the time it does it is a quality problem with a building cause.