Water selection
Define DI, sterile water or WFI appropriately.
Contamination-control claims
Fog Purity, Residue and Process Risk
LN₂ and qualified water avoid the oil or glycol carriers associated with some theatrical fog systems, but that does not justify an unconditional “zero contamination” claim. Purity depends on inputs, equipment condition, handling and the environment.
Use a claim ladder.
| Claim level | Defensible wording | Evidence needed |
|---|---|---|
| Carrier chemistry | No oil or glycol carrier is used in the qualified LN₂/water process | Approved manual and fluid specification |
| Residue expectation | Designed to avoid carrier residue when operated per the approved procedure | Product design and representative use evidence |
| Process suitability | Suitable for the defined controlled environment under the approved risk assessment | Facility qualification and protocol |
| Absolute purity | “Zero particles” or “cannot contaminate” | Generally indefensible without a narrowly defined measurand and test method |
Contamination pathways that remain.
- Improper water quality or container handling.
- Dirty hoses, wands, fittings or storage cases.
- Condensation and droplet deposition near water-sensitive surfaces.
- External contamination introduced during setup or transfer.
- Corrosion, damaged wetted components or unapproved cleaning chemistry.
- Use of the wrong fluid or operation outside the approved manual.
- Bioburden or endotoxin concerns not addressed by a generic “pure water” label.
A stronger procurement requirement.
Specify the required water type, wetted-path materials, cleaning and storage method, certificate expectations, intended cleanroom class, critical surfaces, allowable condensation risk and pre-use inspection. This produces a useful decision; demanding “100% pure fog” does not.
Continue the research
Related technical guidance
Accessories
Control cleanliness through the delivery path.
Claims policy
See how this site handles technical claims.
Applied Physics technical review
Build a defensible fogger requirement
Send Applied Physics the room, process, utilities, documentation and safety constraints—not just a model number.