ISO 5 Standards for Aerospace Component Assembly and Satellite Testing

Particle cleanliness and controlled humidity, temperature and electrostatic discharge (ESD) manifest in the long term degradation of assembly integrity, optical potency and reliability.

An iso 5 rated cleanroom for aerospace delivers more than the air cleanliness assurance. It provides a controlled, verifiable and traceable environment for the total assembly and testing process.

What is an ISO 5 Cleanroom?

Put simply, what is an ISO 5?

iso 14644-1 defines cleanrooms by the maximum permissible concentration of airborne particulates of a certain size. ISO 5 has traditionally aligned to class 100, however, the two standards do not mirror. It is a determination based on defined particulate size and measured concentrations.

For satellite assembly environments, ISO 5 is the baseline for many of the critical operations. Even so, each situation must be classified in accordance with the most recent update to ISO 14644-1 and the specialized project technical requirements.

ISO 5 concentration of particulates (numerical data)

Below is the listing of iso 14644-1:2015 definition of size per unit volume particulate concentration limits. These are the acceptable limits for the cleanroom operational state (at-rest and as-built may be more stringent).

Source: ISO 14644-1:2015, Table 1. Limits apply to the operational state.

ISO 5 is not the same as Total Contamination Control (TCC)

TCC aims to control a wide range of contaminants that may adversely impact aerospace products. These contaminants include particles, molecular contamination, outgassing, ionic, electrostatic, and microbial contamination as well as ESD.

• Personnel – gowning and specific behavior and advanced training
• Materials – outgassing and surface cleanliness
• Equipment – more advanced and better maintained tools and fixtures
• Packaging – cleanliness and handling
• Airflow – controlled patterns and velocities

• Construction surfaces – better working finishes and joints

Why Satellite Assembly Requires a High-Reliability Cleanroom

Sensitive aerospace components

Each component type encounters specific threats in the environment. For high-reliability cleanrooms, protection must be designed to address these vulnerabilities in a systematic way.

Optical payloads – mirror surface particles that result in molecular deposition and lowering of transmittance and scatter example image quality. A single particle at 0.5 μm can be calibrated to a mirror surface scatter.

Electronic modules – ESD discharges of 20V (μm) pose a major threat to sensitive microelectronic components. Coupled with thermal stress and short circuits,

Sensors and Detectors – Surface contamination; sensitivity drift; calibration shift; fluctuations in thermal environment. Many infrared sensors cope better with fluctuating thermal environments during measurement.

Propulsion and Mechanical Assemblies – Particle penetration through precision gaps; contamination of lubricants; assembly tolerance shifting; changes in material and seal performance.

The price of environmental disturbances

Changes in temperature are always coupled with changes in the dimensions of components. After a 1°C shift on a 1 m long structure, expansion can be expected to be ~12 μm, which is large enough to disturb optical alignment.

There are changes in the moisture content of materials; charges may be accumulated on surfaces, as well as contamination of surfaces with particles that may lead to the failure of a test. Absence of environmental data greatly deprives root-cause analysis and audits.

Reliability of a cleanroom is as important as compliance to a given standard

Just one cleanliness test that is passed with the minimum required standards does not mean that the environment can be relied on. The assembly of satellites can mean that performance has to be reliable throughout the seasons, with changing loads, alternating equipment, maintenance, and even when faults are present. The design goal should shift from "pass the test" to "continuously pass the test."

ISO 5, the NASA Standards and Aerospace Cleanroom

ISO Class 14644-1

This standard includes the easy-to-understand framework used to help classify the concentration of airborne particulates and determine acceptance and verification of cleanrooms within the Aerospace industry

ISO Class 14644-2

This portion of the standard outlines the requirement for continued performance and the monitoring plans, testing intervals, and documentation over the performance period. It also addresses the monitoring of critical control points, the management of data trends, and the verification of continued compliance.

ISO Class 14644-3

The following are common verification tests:

• Testing for airborne particulates
• Testing velocity and volumes of airflow
• Testing airflow patterns
• Testing pressure differentials
• Conducting recovery tests
• Testing for leakage of installed HEPA/ULPA filters
• Testing of the cleanroom environment for temperature and humidity

Testing conducted to the specific standards of NASA and additional clientele or customers

NASA documentation often encompasses issues concerning the control of contamination, the operation of cleanrooms, the disposition of materials and personnel, the control of packaged materials, and the testing of such materials. The following are some of the more frequently referenced documents:

• NASA-STD-6001 (NASA Standard for Acceptable limits for materials’ Flammability, Offgassing, and Compatibility of materials)
• NASA SP-8003 (NASA Contamination Control Guidelines for Spacecraft)
• ECSS-Q-ST-70-01C (European Standard Space Product Assurance Contamination Control)
• NASA JSC 20793 (NASA Johnson Space Center Cleanroom Standards)

In addition to these standards, there may be other requirements for the project-specific contractor and also based on the mission customer. Different space missions have varying levels of risk. Different spacecraft subsystems may require different levels of cleanliness and different operational requirements.  It is recommended for design teams to develop a “Standards Matrix” at the earliest possible point in time.

Environmental Parameters for Aerospace ISO 5 Cleanrooms

Management of Air Temperature

The control of temperature has three elements: design set point, range of permissible fluctuation, and uniformity of distribution. Stability can be affected by gain of heat from the containment and the personnel, the opening and closing of doors, the external weather, the heat transfer from the building to the test apparatus (air flows), and so on.

Deiiang™ verified project data support that their systems are capable of maintaining stable air temperature under the specified operating conditions. However, the actual control will depend on the profiles and configuration for each case.

Management of Relative Humidity

High humidity facilitates the corrosion and absorption of moisture by materials and condensation. Low humidity can contribute to a high risk of electrostatic discharge. Humidity management should be coordinated with temperature management, outdoor air control, and the circulation of personnel.

• Cooling and dehumidification
• Reheating
• Humidification
• Fresh-air treatment
• Dew-point management

Control of Molecular Contamination & Outgassing

For optical and microwave payloads, molecular contamination (AMC) is often more critical than particulate contamination. VOCs, silicones, and plasticisers can condense on cold surfaces, thereby degrading optical transmission and causing signal loss.

Key measures to control outgassing include: selection of HVAC elements with low-outgassing gaskets and silicone-free filter media, and the use of materials with an ASTM E595 (TML < 1.0%, CVCM < 0.1%). Regular assessments of surface cleanliness (wipe tests for non-volatile residue) are recommended.

Differential pressure

Pressure differential standards exist between clean zones and their peripheries. The opening of doors, movement of personnel, and the evacuation of equipment can disturb pressure. Most aerospace industry cleanrooms that adhere to ISO 5 standards will have a positive pressure in relation to ISO adjacent spaces.

Airflow and air change strategy

For ISO 5 spaces, design will be influenced by preference of unidirectional flow. Issues of top-supply side-return, top-supply floor-return, FFU arrays, localized work zones, airflow short-circuiting, sources of heat, and equipment obstructions must be solved in the design. Air change rates should not be optimized for the sake of it, but based on the contamination load demands and process requirements.

ESD and molecular contamination

ISO 5 by itself does not address ESD. Grounding and anti-static materials are required for low humidity environments. HVAC materials, sealants, coatings, and filters can become contamination sources. Optical assemblies and sensitive payloads also need molecular contamination control.

HVAC Architecture for a High-Reliability Aerospace Cleanroom

Sectioning of an air handling unit

A typical air handling unit is made up of fresh-air intake, a pre-filter, cooling coil, heating/coiling, a humidification section, a fan section, a fine filter, HEPA filter, or terminal filter, and monitoring/control. A modular block of Deiiang™ can be configured to provide the listed functional sections, based on a project’s requirements, as designed by Jason.peng and the engineering team.

Variable-speed control

Variable-speed systems respond to partial loads, door openings, personnel and equipment changes, night or standby modes, filter resistance increases, and shifts in outdoor climates. Deiiang™ variable-frequency technology enables continuous capacity adjustment with no steps across a broad operating range, which leads to energy loss when the load is low.

Redundancy and continuous operation

• N+1 cooling capacity
• Standby fan
• Dual power supply
• Automatic changeover
• Backup control logic
• Critical alarm notification
• Emergency operating mode
• Maintenance without total shutdown

Redundancy goes beyond equipment and system supply. It includes critical equipment, control, power, and maintenance integration for sustained continuity.

Efficiency and lifecycle cost

Variable-speed systems reduce energy loss associated with partial load. The energy costs associated with fan power loss due to filter pressure loss, the fresh air load, and dehumidification are also important to consider. Heat recovery options as well as energy costs related to maintenance, spare parts, and unplanned downtimes are assessed on their total lifecycle costs.

HEPA filtration and airflow

Pre-filter and fine filter and terminal HEPA strategy

A three-stage filtration logic is standard. The pre-filter protects downstream equipment. Medium or fine filtration reduces the HEPA load and confirms the terminal cleanliness. This strategy is common in IS0 Class 4 through 9 cleanrooms and is used to maximize the performance and lifetime of the filter.

HEPA filter performance

The method of testing particles and the grade of the filter affect the performance of the filters. Commonly noted are the filter class, test particle size, the standard of the test, the initial and final resistances, and the method of leak testing. Deiiang™ terminal HEPA filtration units are tested using ISO 14644-3 and EN1822.

Airflow Visualization

Adequate airflow in working zones is essential in preventing contamination of the facility’s products. Recirculation and eddies should be avoided. Work equipment should also not create contaminated areas that cannot be cleaned. Smoke tests and airflow visualizations help determine all of the above.

Filter Integrity and Maintenance

For the space application of a satellite assembly environment, it is essential that seal integrity is controlled after it is sealed using filters. This includes integrity testing, inspections of seals, monitoring pressure differential trends, scheduled changes and re-validations after a change, and numbered filters maintained with traceable records.

Monitoring Cleanrooms and the Control of Data with Traceability

The continuous monitoring of the cleanroom environment is controlled and recorded.

• Temperature and relative humidity
• Differential pressure within the cleanroom
• Particles
• Airflow and the pressure drop across the filters
• Status of fans and compressors and doors
• Status of alarms and a black box

Black box or long-term data recording

Deiiang™ system architecture helps provide long trusted and audit-ready traceability. Operating data, alarm history, equipment start/stop, temperature and humidity trends, filter pressure trends and errors are monitored and recorded.

Data can be stored on site, or on the cloud, be exportable, and have controlled access customizable to the user’s data management needs.

There is a defined logic for alarms and responses.

Sensor detects a change --> controller identifies anomaly --> system issues a pre-alarm --> change occurs --> operator is informed of limit breach --> event recorded and anomaly investigated.

Deiiang Solution for Aerospace ISO 5 Applications

Solution positioning

As a partner, Deiiang™ is a supplier of cleanroom HVAC equipment, an air handling unit manufacturer, an air handling unit supplier, a temperature and humidity control solution supplier, and an integrated environmental control system supplier.

Product architecture

Deiiang™ offers air handling units, modular AHUs, fresh air units, fan filter units, HEPA terminal units, variable-frequency devices, temperature and humidity control units, building management system (BMS) integration and monitoring systems, as designed by Jason.Peng and the Deiiang™ engineering team.

Verified technical data module

Case Study: iso 5 environment for Satellite Component Assembly

Project background

An ISO 5 controlled environment was built for the assembly and inspection of sensitive aerospace components. The facility needed the ability to maintain stable temperature and humidity with low particulate levels, pressure differentials, and a controlled airflow with continuous monitoring of the environment.

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Customer requirements

• Maintain stable temperature and humidity
• Maintain low particle concentration
• Maintain airflow as required in work zones
• Continuous service
• Fault alarm with capture
• Simplified filter change
• Provide validation and commissioning services

Project challenges

Challenge 1: Cleanroom airflow of a large volume – equipment and tools disrupted a uniform airflow; personnel activity created local disturbances; upper areas risked contamination accumulation.

Challenge 2: Frequent changes to cooling and dehumidification load. Equipment starts and stops, door openings, shifts in personnel, and outdoor humidity affected the treatment of fresh air.

Challenge 3: Customer requested tight temperature and humidity control limits. Threshold, measured, and test parameters were compared.

Challenge 4: Data traceability was enhanced through requirements for data retention, sampling frequency, alarm logs, export formats, and access controls.

Deiiang's Solution

Project Results

• Was able to classify particles
• Consumption of energy is 28.4% below the baseline for fixed speed
• Availability of equipment is above 99%
• The commissioning was done as required, and within the schedule.
• Stability of temperature was achieved within ±0.2°C
• Stability of humidity was achieved within ±2.5% RH
• All tests were passed successfully
• Time to recover after testing was less than 12 min with a ratio of 100:1
• System pressure was stable
• Leakage test of the filters passed

Persona Scenario: The Satellite Assembly Facility Manager

Name: David Chen
Role: Cleanroom and Aerospace Facility Manager
Facility: Satellite Payload Assembly Plant
Responsibility: Control of the Environment, Validation, Continuity of Production, and Readiness for Audit

The satellite integration team executes a critical operation for the optical payload at 2:15AM. The Facility Manager prefers not to have to be present and make the necessary adjustments to the system for every change in the outdoor humidity as well as every time the door to the cleanroom is opened. The Facility Manager prefers an HVAC system that would automatically adjust because it would give a warning of an impending breach of target parameters, and it would be able to provide logs of the parameters for review at a later time.

The pain points for David Chen are that he does not want to have the HVAC system adjusted manually for every breach of environment control. He needs to identify when the controls are breached and wants to be able to correlate the data from the HVAC system with the data from the production line. He also needs continuous operation for the HVAC system with no intervention for maintenance, and he needs to have easy access to the logs of the system during an external audit.

What does he want from the HVAC supplier? Knowledge of aerospace assembly processes, genuine test data, validation and commissioning assistance, the ability to integrate systems, and the capability of providing long-term service and warranty support, including spare parts.

Validation of an Aerospace ISO 5 Cleanroom

Design Qualification

User requirements, cleanroom class, process load, capacity and design of the HVAC system, pressure gradient, filter arrangement, control logic and design, and redundancy.

Factory Acceptance Testing

Design of the equipment including dimensions, the design of airflow and pressure with required characteristics, leakage rates with acceptable fan design and performance, design of control, alarms, and instrumentation with regard to their calibration and the proper placement and installation of filters.

Site Acceptance Testing

Cleanliness of air, control of airflow with regard to velocity and pressure differentials, the measurement and control of air temperature and humidity, and assessment of visual airflow, HEPA filter integrity, recovery time, and measurement and control of noise and illumination.

Recovery time 100:1

Recovery time is the time required for a cleanroom to achieve the designated class of cleanliness after having been contaminated. It is required to be ≤15 to 20 minutes for ISO 5 for the 100:1 recovery time (from 100 times to 1 time the limit). This is the upper limit and is a test of the capability of the HVAC system. Recovery time is of particular importance for satellite assembly and disassembly as the large components of a system are moved into and out of the cleanroom.

Recovery time is a function of the rate of air changes, filter performance, and air distribution. In validated projects, Deiiang™ systems have achieved recovery times of 12 minutes or less.

Operational Qualification

Recovery time is the time required for a system to return to an acceptable state, as determined by the recovery of the system, the operation of the equipment, and the correction of any interruptions. This qualification is done during the normal operation of the system. If the system is required to operate under abnormal conditions (for example, the opening of doors or movement of personnel), it must meet the system requirements, including the recovery of the system and the functioning of the alarms.

Common Errors in Aerospace cleanroom design

Interactive Items

Commercial ROI Estimator (ACH + Energy + Savings)

Frequently Asked Questions

References

• ISO 14644-1:2015 – Classification of air cleanliness by particle concentration
• ISO 14644-2:2015 – Monitoring to provide evidence of continued performance
• iso 14644-3:2019 – Test methods
• NASA-STD-6001 – Material offgassing & compatibility
• ECSS-Q-ST-70-01C – Space product assurance: contamination control
• Deiiang™ product documentation and verified test reports (available upon request)

© 2026 Deiiang™ — Engineered by Jason.peng and the Deiiang cleanroom team. All specifications subject to verification against latest standards and project requirements.