Overview
ISO 11844-3:2020 - "Corrosion of metals and alloys - Classification of low corrosivity of indoor atmospheres - Part 3" specifies methods for measuring the environmental parameters used to classify the corrosivity of indoor atmospheres. The standard defines how to monitor humidity, temperature, airborne gas and particle contaminants, and dry-deposition/air-flow parameters that influence corrosion rates of metals and alloys in indoor environments.
Key topics and technical requirements
- Measured parameter groups
- Humidity and temperature (including temperature–humidity complex and condensation frequency)
- Airborne gas contaminants (concentration and deposition)
- Airborne particle contaminants (volumetric and deposited particles)
- Dry deposition velocity and air flow
- Measurement methods
- Continuous gas concentration instruments
- Active samplers (pumped air through an absorbent; laboratory analysis)
- Passive samplers (diffusive samplers based on Fick’s first law)
- Gas-deposition equipment for direct deposition rates
- Sampling and placement
- Place instruments where the corrosivity problem exists; for general assessment use a central open area
- Continuous instruments: protect from tampering; sample tubing (PE or PTFE) not to exceed 2 m
- Passive samplers: allow free air movement; open end facing downward
- Deposition equipment: sheltered from settling particles
- Duration and reporting
- Preferred measuring period: one year to capture seasonal variation; minimum one month per season
- Humidity/temperature: report monthly average, maximum and minimum; calculate time in specified intervals and condensation frequency
- Active sampler: sampling time ≥ 1 week; weekly data converted to monthly averages
- Units: gas concentrations typically in µg/m3; deposition in mg·m−2·d−1
- Example formula for active samplers: C = m / V (C = average concentration, m = mass absorbed, V = air volume sampled)
- Detection limits
- Typical continuous instruments: detection in the ~10^−9 (volume fraction) range; specialized units may reach one-tenth of that
- Active sampler weekly mean detection: approx. 0.1 µg/m3 (dependent on analytical sensitivity)
Practical applications
- Characterizing indoor corrosivity for archives, museums, heritage conservation and storage facilities
- Risk assessment and mitigation planning for electronics, metal components, and industrial equipment indoors
- Designing environmental control strategies (HVAC, dehumidification, filtration)
- Baseline and compliance monitoring in cleanrooms, laboratories and sensitive manufacturing areas
Who should use this standard
- Corrosion engineers and materials scientists
- Conservation professionals and collection managers
- Facility and asset managers (industrial, cultural heritage, archival)
- Indoor air quality laboratories and consultants
- HVAC and environmental control designers
Related standards
- ISO 11844 series (other parts addressing corrosivity classification and test methods)
- ISO 16000 series (indoor air sampling and analysis methods referenced for pollutant sampling strategies)
Keywords: ISO 11844-3:2020, indoor corrosivity measurement, corrosion of metals, passive sampler, active sampler, continuous gas measurement, humidity monitoring, deposition rate, indoor air contaminants.
Open preview (PDF)Corrosion of metals and alloys — Classification of low corrosivity of indoor atmospheres — Part 3: Measurement of environmental parameters affecting indoor corrosivity
