An ISO Class 8 cleanroom is classified under ISO 14644-1 based on the concentration of airborne particles. At 0.5 micrometers (µm) and larger, the maximum concentration is 3,520,000 particles per cubic meter of air.
ISO Class 8 defines an airborne particle cleanliness level. Maintaining that classification normally requires a broader system of HVAC controls, pressure relationships, cleaning procedures, personnel practices, monitoring, and periodic testing. The specific controls depend on how the room is used, and which regulatory, quality, and process requirements apply.
ISO Cleanroom Classification Overview
ISO 14644-1 defines nine air-cleanliness classes, from ISO Class 1 through ISO Class 9. Lower class numbers permit fewer airborne particles. ISO Class 8 is commonly used for controlled manufacturing, support and preparation areas where moderate particulate control is appropriate.
A room should be described by both its ISO class and its occupancy state. ISO 14644-1 recognizes as-built, at-rest and operational states. The customer and supplier should agree on the state used for classification because a room may meet ISO Class 8 at rest but not during normal operations.
ISO Class 8 Particle Limits and Monitoring
For ISO Class 8, the maximum permitted concentrations include 3,520,000 particles/m³ at ≥0.5 µm, 832,000 particles/m³ at ≥1.0 µm and 29,300 particles/m³ at ≥5.0 µm. The older Federal Standard 209E term “Class 100,000” is still used informally, but ISO Class 8 is the current classification terminology.
Classification testing uses a calibrated light-scattering airborne particle counter and a sampling plan based on the room area, selected particle sizes and agreed occupancy state. Every required sampling location must meet the applicable class limit; averaging results do not rescue a failing location.
Routine monitoring provides ongoing evidence that the cleanroom remains in control between classification tests. A documented, risk-based monitoring plan should define the parameters, locations, frequencies, alert levels, and action levels appropriate for the process. The plan may include particle counts, pressure, airflow, or other indicators that measure or affect airborne particle concentration.
Environmental and HVAC Controls
An ISO Class 8 room needs an air-handling system capable of maintaining the specified particle class under the agreed operating conditions. HEPA filtration is common, while filter layout, airflow pattern and supply-air volume are selected to address particle generation, occupancy, heat load and recovery needs. Air-change rates such as 15–25 Air Changes Per Hour (ACH) may be useful as a starting design, but the final rate should be justified for the room and its application.
Pressure differentials are commonly established to control contamination movement between adjacent spaces. Positive pressure is generally used to protect cleaner areas from less-clean surroundings, while negative pressure may be appropriate when hazardous materials must be contained. Setpoints should support the facility’s contamination-control strategy and applicable requirements.
Temperature and relative humidity criteria help support process stability, material requirements, personnel comfort, and gowning practices. Facilities should define justified operating ranges and verify that the HVAC system can maintain them under expected occupancy and process loads.
Personnel Practices and Gowning
People are often the largest source of particles in an occupied cleanroom. ISO Class 8 gowning commonly includes hair and beard covers, low-shedding garments, and shoe covers. Facilities should select garments, gloves, and entry procedures based on personnel activity, product risk, and applicable industry requirements.
Personnel should be trained in hand hygiene, gowning sequence, movement, material transfer, and response to excursions. The gowning area and pressure cascade should support the facility’s personnel flow and contamination-control strategy rather than rely on a generic layout.
Cleaning, Disinfection and Maintenance
Cleaning procedures should define the surfaces, methods, tools, agents, frequencies, responsibilities, and required records. Low-lint wipes and mops, compatible cleaning agents, and a clean-to-less-clean sequence are common practices. Frequencies should reflect room use, contamination risk, monitoring trends and applicable regulatory or quality requirements.
Cleaning removes soil and residue, while disinfection controls microorganisms. Where microbial control is needed, the program should address agent efficacy, material compatibility, contact time, application method, and residue management. The process and regulatory framework determine whether routine disinfection, sporicidal treatment, or agent rotation is appropriate.
ISO Class 8 Testing and Certification
ISO Class 8 classification is demonstrated through airborne particle concentration testing in accordance with ISO 14644-1. A broader cleanroom qualification program commonly includes airflow volume or velocity, room pressure differential, HEPA filter integrity, airflow visualization and recovery testing. Together, these tests verify particle classification and confirm that the facility performs as designed.
Periodic testing intervals should be established through the applicable regulation, quality system, customer specification, and risk assessment. Many facilities perform certification annually or more frequently based on industry requirements and room criticality. Additional testing is appropriate after significant HVAC changes, construction, major maintenance, or an unexplained loss of control.
Common Compliance Challenges
Common challenges include poorly defined occupancy states, incomplete sampling plans, unjustified design setpoints, incomplete documentation, and particle excursions during normal activity. Programs are stronger when they connect to clear user requirements, appropriate facility qualification, trained personnel, risk-based monitoring, and routine trend review.
Contact TSS
TSS provides cleanroom classification, certification and controlled environment testing to help facilities verify ISO Class 8 performance and establish practical testing and monitoring programs. Contact TSS to discuss your cleanroom requirements.
