Frequently Asked Questions

ISO 14644-1 classifies cleanrooms based on the maximum allowable concentration of airborne particles per cubic meter at specified particle sizes. Classification is determined by measuring particle counts at defined sampling locations and comparing them against the standard's concentration limits. The standard defines classes from ISO 1 (cleanest) to ISO 9, with each class allowing approximately 10 times more particles than the class below it.

Particle deposition rate (PDR) is the number of particles that settle onto a surface per unit area per unit time. Unlike airborne particle concentration, PDR directly measures the contamination risk to your product. A product surface exposed in a cleanroom accumulates deposited particles over time, and the PDR determines how many particles your product will collect during its exposure window.

An 'at rest' classification is measured when the cleanroom is fully operational with equipment running but no personnel present. An 'in operation' classification is measured during normal production with personnel working inside. Particle counts are typically 5 to 100 times higher during operation due to human activity, which is why both states are important for understanding your actual contamination risk.

The critical particle size depends on your product's smallest functional feature or the size at which a particle causes a defect. For electronics, this is often related to trace width or spacing. For optical components, it relates to the wavelength of light used. For medical devices, it may be driven by biocompatibility or functional requirements. Start with the smallest defect-causing particle size your quality data identifies.

The acceptable particle count depends on your product's sensitivity, defect tolerance, and quality requirements. Some products like semiconductor wafers may tolerate zero critical-size particles, while others like automotive components may accept several. You can use the Product calculator to determine the PDR level and ISO class needed for your specific particle acceptance criteria.

Larger particles are more likely to cause visible or functional defects, but smaller particles are far more numerous in any environment. The relationship is defined by your product's critical dimensions - a particle must typically be at least 10-25% of a critical feature size to cause a functional defect. Understanding this relationship helps you focus contamination control on the particle sizes that actually matter for your product.

The calculator uses your product specifications (surface area, exposure time, critical particle size, and acceptable particle limits) to compute the maximum allowable particle deposition rate. It then determines which ISO cleanroom class can achieve that deposition rate and provides a risk assessment. The Cleanroom tab evaluates your facility's actual performance based on room dimensions, ventilation, personnel, and garment type. Try the example analysis to see it in action.

For a product risk assessment you need four key inputs: the critical particle size (in micrometers), the maximum number of acceptable particles on your product, the exposed product surface area, and the exposure time during manufacturing. Optional inputs include a secondary (smaller) particle size and sample sensor parameters. You can try the example analysis to see how it works before entering your own data.

PDR Level (Particle Deposition Rate Level) represents the maximum rate at which particles can deposit on your product while staying within your acceptance criteria. It is calculated by dividing your maximum acceptable particle count by the product surface area and exposure time. The resulting PDR Level directly maps to an ISO cleanroom class, telling you what environment your product requires.

The calculator applies validated models based on ISO 14644 standards and empirical particle deposition research. Results provide a reliable engineering estimate for cleanroom planning and risk assessment. Actual conditions may vary based on factors like airflow patterns, equipment layout, and process-specific particle generation. We recommend validating results with on-site particle deposition measurements for critical applications.

Yes. The calculator works for any controlled environment where particle contamination is a concern, including production halls, packaging areas, and assembly rooms. If the calculated ISO class is 8 or 9, it indicates that standard industrial conditions may be sufficient for your product. The results help you determine whether investing in a cleanroom is necessary or if simpler contamination controls will meet your requirements. Try the calculator with your product specifications.

The Product and Cleanroom calculators are free to use with basic results including your risk level and recommended ISO class. The Pro plan unlocks the full analysis with detailed PDR values, monitoring specifications, the Performance tab, PDF report generation, and simulation history. A 24-hour access option is also available for one-time assessments. See the pricing page for details.

The Pro plan includes full access to all calculator results without gating, the Performance (monitoring) tab with sensor configuration recommendations, downloadable PDF reports for all analysis types, the ROI calculator with scenario modeling, simulation history and comparison tools in your dashboard, and priority support. Visit the pricing page for current pricing details.

Yes. Pro plan subscribers and 24-hour access users can download PDF reports for each analysis type (Product, Cleanroom, ROI, and Performance). Reports include all input parameters, calculated results, risk assessments, and recommendations in a format suitable for internal documentation, quality audits, or management presentations.

The calculator is built on ISO 14644-1 (cleanroom classification) and ISO 14644-3 (test methods) standards. Particle deposition rate calculations are based on established aerosol science models for gravitational settling and diffusion. For pharmaceutical and medical applications, the methodology aligns with EU GMP Annex 1 grade requirements. Read more about our methodology.

The calculator determines your required PDR limit from your product specifications, then maps that limit to an ISO class using the relationship between airborne particle concentration and deposition velocity. Each ISO class has a defined maximum airborne particle concentration, and combined with particle settling physics, this translates to a predictable deposition rate. The ISO class whose concentration limit produces a PDR at or below your required limit is your recommended classification.