Brookhuis Applied Technologies

Ask a quality manager why their cleanroom is classified the way it is, and you will often hear a version of the same answer: to be safe. It is an honest answer, and an expensive one. Behind this lies a decision made without the one crucial piece of information that should underpin it, and that missing information costs manufacturers energy, money, and revenue every day.

This is the case for a different approach: making contamination control decisions based on evidence rather than caution.

The problem with 'to be safe'

When a company designs a cleanroom for a new product, it faces a hard question with expensive consequences: how clean does the environment actually need to be? A stricter ISO class means more filtration, more air changes per hour, more energy, and higher running cost for the entire life of the facility. A class that is too loose means contamination, rejected product, and lost yield.

Faced with that asymmetry, most teams do the understandable thing. They over-specify. If ISO 6 might be needed, build ISO 5. If in doubt, increase air changes. The logic feels prudent, but it rests on not knowing something specific, and paying to cover the gap.

That gap has a name. It is the critical particle size. Important are the impact of surface cleanliness and operations.

The particle that actually matters

Not every particle is a threat. A speck that would destroy a semiconductor feature is completely harmless to a molded plastic component. The particle size that genuinely threatens a given product, sometimes called its critical particle size, or its "particle killer" , is what should determine how clean its environment needs to be.

Here is what makes it decisive: two products in the same cleanroom can carry entirely different contamination risks, because their critical particle sizes differ. Clean air to the wrong particle size and you are either spending money protecting against particles that never mattered, or missing the ones that do.

Most over-engineering traces back to this single unanswered question. If you do not know which particle is the killer, the only safe option is to protect against all particles, and that is precisely why classifications and costs turn out higher than necessary.

The cost of over-engineering

The evidence-based alternative

What this looks like in practice

A manufacturer preparing to specify a cleanroom for a new product starts not with a target class, but with a question: what is the critical particle size, and how much deposition can this product tolerate over its exposure time? But also, how can the exposure time be reduced? From those inputs, the required deposition rate and ISO class follow directly. Often the answer confirms that a less strict class is sufficient and the energy and cost savings that follow are real, measurable, and permanent.

For an existing facility, the same logic runs in reverse. Measure what is actually depositing on critical surfaces during operation, compare it to what the product can tolerate, and you learn whether your current class is correct, too strict, or too loose. Many facilities discover they have been paying for a cleaner class than the product ever needed.

And once the target is set from evidence, monitoring alarm limits stop being arbitrary. They become the specific deposition rate the product cannot exceed, so an alarm means a real risk, and a quiet system means genuine compliance.

Ask a quality manager why their cleanroom is classified the way it is, and you will often hear a version of the same answer: to be safe. It is an honest answer, and an expensive one. Behind this lies a decision made without the one crucial piece of information that should underpin it, and that missing information costs manufacturers energy, money, and revenue every day.

This is the case for a different approach: making contamination control decisions based on evidence rather than caution.

The problem with 'to be safe'

When a company designs a cleanroom for a new product, it faces a hard question with expensive consequences: how clean does the environment actually need to be? A stricter ISO class means more filtration, more air changes per hour, more energy, and higher running cost for the entire life of the facility. A class that is too loose means contamination, rejected product, and lost yield.

Faced with that asymmetry, most teams do the understandable thing. They over-specify. If ISO 6 might be needed, build ISO 5. If in doubt, increase air changes. The logic feels prudent, but it rests on not knowing something specific, and paying to cover the gap.

That gap has a name. It is the critical particle size. Important are the impact of surface cleanliness and operations.

The particle that actually matters

Not every particle is a threat. A speck that would destroy a semiconductor feature is completely harmless to a molded plastic component. The particle size that genuinely threatens a given product, sometimes called its critical particle size, or its "particle killer" , is what should determine how clean its environment needs to be.

Here is what makes it decisive: two products in the same cleanroom can carry entirely different contamination risks, because their critical particle sizes differ. Clean air to the wrong particle size and you are either spending money protecting against particles that never mattered, or missing the ones that do.

Most over-engineering traces back to this single unanswered question. If you do not know which particle is the killer, the only safe option is to protect against all particles, and that is precisely why classifications and costs turn out higher than necessary.

The cost of over-engineering

The evidence-based alternative

What this looks like in practice

A manufacturer preparing to specify a cleanroom for a new product starts not with a target class, but with a question: what is the critical particle size, and how much deposition can this product tolerate over its exposure time? But also, how can the exposure time be reduced? From those inputs, the required deposition rate and ISO class follow directly. Often the answer confirms that a less strict class is sufficient and the energy and cost savings that follow are real, measurable, and permanent.

For an existing facility, the same logic runs in reverse. Measure what is actually depositing on critical surfaces during operation, compare it to what the product can tolerate, and you learn whether your current class is correct, too strict, or too loose. Many facilities discover they have been paying for a cleaner class than the product ever needed.

And once the target is set from evidence, monitoring alarm limits stop being arbitrary. They become the specific deposition rate the product cannot exceed, so an alarm means a real risk, and a quiet system means genuine compliance.

Evidence-Based Contamination Control Decisions

Evidence-Based Contamination Control Decisions

Evidence changes the question