Technology-level decision matrix
| Technology | Typical strengths | Primary constraints | Applied Physics pathway |
|---|---|---|---|
| Ultrasonic water fog | On-demand operation; DI/WFI/approved water; portable; scalable output. | Contains microscopic water droplets; water quality and drying matter; may not suit moisture-sensitive areas. | CRF2, CRF3 and CRF6 categories. |
| LN₂ plus water | Dense, high-purity fog; longer visual distance; strong fit for critical cleanroom studies. | Cryogenic handling, oxygen-displacement review, logistics, weight and operating procedure. | AP30 self-pressurized; AP35 passive/dewar; larger AP-series platforms as required. |
| Dry ice plus heated water | Can operate without live electrical connection during fog production; simple visual tracer. | Output may decay once started; dry-ice handling; heated water; less on-demand control. | Legacy/limited category; compare against current CRF or AP systems. |
| Glycol or proprietary aerosol | Very portable; long-lasting visible tracer; compact handheld formats. | Fluid chemistry, residue/exposure, process compatibility and cleanroom acceptance require review. | Not the primary current AP cleanroom platform. |
| Smoke tubes / chemical smoke | Small, localized and simple for some field checks. | Chemical exposure, residue, one-time use and application restrictions. | Use only under the controlling safety method. |
The eight variables that matter most
Purity and process exposure
Can water droplets, cryogenic fog or chemical aerosol contact the space, product or equipment?
Output and visibility
How much fog is needed to remain visible through the actual airflow and lighting?
Source momentum
Can the delivery be tuned so the tracer does not manufacture the pattern?
Runtime and refill
How long must the study run, and can the system be refilled without disrupting the protocol?
Control
On/off, variable output, airflow velocity and remote operation may determine usability.
Delivery geometry
Point, curtain, split hose, long hose or multiple outputs change the study.
Operating logistics
Power, LN₂ access, water quality, transport, setup time and operator training.
Evidence requirements
General diagnosis, formal cleanroom study, fume-hood testing and HVAC TAB have different proof burdens.
Keep the current categories distinct
The CRF family is the current Applied Physics ultrasonic pathway. The AP family is the LN₂ pathway. Within the AP family, the AP30 is self-pressurized and the AP35 is passive/dewar style. Do not describe AP30 as the automatic successor to AP35; the correct choice depends on application and LN₂ logistics.
Current specifications and warranty terms should be reconfirmed at quotation and before being incorporated into a protocol.
Questions this page should settle
Which technology creates the cleanest fog?
Purity depends on the complete system, approved liquids, handling, materials and environment. LN₂ plus approved water is commonly selected for high-purity cleanroom visualization; water-only ultrasonic systems are also widely used.
Is a chemical aerosol automatically unsafe?
No blanket conclusion is appropriate. The exact fluid, exposure, residue, process and facility controls must be reviewed. Critical environments often impose tighter constraints.
Turn the airflow question into an equipment specification.
Send the environment, scale, purity constraint, target visibility, delivery geometry, runtime and operating restrictions. Applied Physics can compare current ultrasonic and LN₂ platforms without treating one model as a universal answer.