Quick Answer: There is no such thing as an ISO Class 5 coating. ISO 14644-1 classifies air, not materials: Class 5 means no more than 3,520 particles of 0.5 micron or larger per cubic metre. A coating contributes to achieving that classification, but it is never itself classified.
Nothing, in the sense the question implies — because there is no such thing as an ISO Class 5 coating. The classification is a measurement of air, not a certification of materials, and no coating carries it. Understanding why changes what you should be asking a manufacturer for.
What ISO Class 5 actually measures
ISO 14644-1 classifies cleanrooms by the concentration of airborne particles. ISO Class 5 permits no more than 3,520 particles of 0.5 micron or larger per cubic metre of air. It is the classification that replaced the former US Federal Standard 209E Class 100.
Read that definition again with a specification in hand. It describes a condition of the air in an operating room, measured by sampling. It says nothing about what the walls are made of, what they are coated with, or how that coating was tested.
Other parts of the ISO 14644 family address design, construction and surface cleanliness. But the number everyone quotes — "ISO Class 5" — comes from Part 1, and it is an airborne particle count.
Why "ISO Class 5 rated coating" is a marketing phrase
A coating cannot hold a classification that is only measurable as a whole-room, in-operation condition. What a coating can do is contribute to achieving it, or undermine it.
This matters practically, not pedantically. If a submittal claims a product is "ISO Class 5 certified," that claim has no issuing body behind it, and accepting it means you have not actually established the thing you needed to establish. The useful question is not "is this coating Class 5" but "what test data supports this coating in a Class 5 environment, and does it match my cleaning regime."
What the coating genuinely has to do
Four things, none of which appear in the classification table:
Not shed. A coating that chalks, powders or releases fibres is a particle source inside the envelope you are trying to control. This is the direct link between the coating and the classification — and it is why film integrity over time matters more than the initial reading.
Not outgas into the space. Volatile emission from the film is a contamination route in its own right, and in some semiconductor and pharmaceutical processes molecular contamination matters as much as particulate. Ask for emissions data, not a VOC content figure — those are different tests answering different questions.
Survive the cleaning regime. This is where coatings actually fail in service, and it is almost always underestimated at specification.
Be monolithic in practice, not just in the field. A coating that performs perfectly across a flat wall and fails at the coving, the penetration or the door frame has not delivered a cleanable envelope.
The cleaning regime is the real specification
Classified spaces are not cleaned with a general-purpose detergent. They are cleaned on a rotation, and in pharmaceutical environments that rotation typically includes a sporicidal agent, because rotating chemistries is how resistant organisms are prevented from establishing.
Sporicides are aggressive by design. A coating that tolerates a mild detergent indefinitely may discolour, soften, embrittle or lose adhesion under repeated exposure to an oxidising sporicide — and the failure is cumulative, so it appears months into service rather than at handover.
The question to put to a manufacturer is therefore specific, and it is not "is this suitable for cleanrooms." It is: here is our disinfectant rotation, here are the concentrations and contact times, here is the frequency — what test data do you have against this. A manufacturer who cannot answer that has not tested for your application, whatever the data sheet says in general terms.
Detailing beats product selection
Most cleanroom coating failures are geometric rather than chemical. The coating survives; the assembly does not.
- Coving at wall-to-floor and wall-to-ceiling junctions, so there is no square internal corner to trap particulate and resist wiping
- Penetrations — conduit, sprinkler, gas, data — sealed and detailed as part of the coating system rather than as a separate trade's afterthought
- Door frames, view panels and pass-throughs, where dissimilar materials meet and movement concentrates
- Termination at equipment bases and floor drains
- No ledges, exposed fasteners or open joints anywhere in the envelope
A monolithic surface is a detailing outcome. It is not a property of the product in the bucket.
Application conditions are part of the result
The last item is the one most often left out of a specification: a classified space cannot be achieved by a coating applied in uncontrolled conditions.
Preparation generates dust. Curing generates emissions. Traffic through the space carries contamination in. The sequence, the temporary containment, the filtration in place during the work, and the clean-down and re-qualification before hand-back are all part of delivering the room — and they belong in the scope of work with the same specificity as the product.
What to require in the specification
- Manufacturer test data for particle shedding and for emissions, as reports rather than claims
- Documented chemical resistance against your actual disinfectant rotation, at your concentrations and contact times
- The coving and penetration details drawn, not described
- Application-phase environmental controls, containment and filtration
- The clean-down and re-qualification protocol, and who owns it
- Repair procedure and touch-up compatibility, because the envelope will be breached during its life and a repair that cannot be made cleanly is a design defect
The short version
Specify the environment and the regime, and require evidence against both. A supplier who responds with a classification number has answered a question you did not ask.