ISO 10121-3: The first ever classification system for molecular filters in ventilation systems
While most people usually associate air pollution with outdoor environments, it is less known that indoor environments are not immune to similar threats. Indeed, various pollutants, including a range of gases, often infiltrate indoor rooms via ventilation systems (HVAC). To tackle this invisible issue and to improve the air quality, specialised molecular filters ensure that harmful gases such as ozone, nitrogen dioxide, sulphur dioxide, or hydrocarbons (such as e.g. toluene) do not enter indoor facilities. The new ISO 10121-3 standard acts as a reliable benchmark for a.m. molecular filters. It rigorously tests their efficiency and provides users with a clear rating they can trust. This new classification of air filters simplifies the task of choosing the right filter to ensure we purify the air we breathe indoors.
ISO 10121-3 for molecular filters in ventilation systems
The ISO 10121 series is key in molecular air filtration, providing standardised test methods to fully measure the effectiveness of molecular filter media, analog to ISO 16890 for particle filters. Its primary goal is to lay out the performance of these filters in a way that's both clear and understandable for prospective buyers during their selection process. To measure the filtration efficiency and capacity, specific test procedures help evaluate how effectively and efficiently a filter or its media can purify the air.
- The ISO 10121-1 standard focuses on specific testing methods for molecular filter media. Here, the central components of the filters are examined.
- ISO 10121-2 outlines tests for molecular filters to assess their performance and confirm their efficacy in targeting specific pollutants.
In October 2022, ISO 10121-3 was established, setting standardised test protocols for molecular filters and introducing a comprehensive classification system. This standard provides benchmarks for filter effectiveness and capacity in purifying outdoor pollutants, thereby supporting ventilation system operators and owners in choosing filters tailored to local air pollution and specific system requirements.
The ISO 10121-3 test for most common gaseous air pollutants
The ISO 10121-3 classification system uses a selection of four of the most prevalent pollutant gases commonly encountered in outdoor air as a benchmark to mainly evaluate the efficiency of activated carbon filters.
- Greenhouse gas
- Generated by UV light and combustion processes.
- Irritates lungs and eyes, potential for respiratory diseases.
- Produced by fossil fuel combustion processes, including industrial activities.
- Harms the lungs, may cause respiratory diseases.
- Originates from combustion processes.
- Contributes to haze and acid rain.
- Raises infection susceptibility, impairs lung function and may exacerbate asthma attacks.
- Emitted from combustion processes and found, for example, in solvents and paints.
- Represents volatile organic compounds (VOCs) in ISO 10121-3.
- May cause acute and chronic health issues, including a heightened cancer risk.
How the classification of molecular filters according to ISO 10121-3 works
The ISO 10121-3 standard provides a systematic test procedure to classify a variety of different air and gas filters. It is critical to route the entire airflow through the filter before starting the test, ensuring there is no bypass that could affect its accuracy. The test involves measuring the concentration of gases before they enter the filter (upstream) and after they've passed through (downstream), in order to assess filter performance.
Initial efficiency of the new filter
During the first stage of the ISO 10121-3 test procedure, filter efficiency is tested using low concentrations of test gas. Filters that show a drop in performance exceeding 5 percent under these minimal conditions are automatically disqualified from further testing, as such an initial efficiency loss is considered as insufficient.
Classification of air filter performance during operation
The second phase of the testing process is crucial and includes filters being subjected to specific test gas concentrations. Test gas concentration remaining downstream of the filter is then measured. Filters are considered to have 100 percent efficiency if no gas is detectable in the air flow, once it has passed the filter.
- During regular testing, the concentration of the test gas is monitored until the filter's efficiency for removing the test gas is reduced to 50 percent.
- In cases where the filtered air contains more than 50 percent of the initial gas concentration at the beginning of the test, measurements are conducted until the filter's performance reaches 0 percent efficiency, indicating a constant gas concentration.
Determination of the performance class
Ultimately, the filter's performance is assessed based on the amount of test gas it has already filtered out. The ability to sustain high-quality performance over time results in a higher rating for the filter within the ISO 10121-3 classification system.
- HD (heavy duty): Designed for challenging conditions with heavy contamination, such as heavily polluted areas or environments where a high level of purity is critical. HD filters have a service life that is 16 times longer than LD (light duty) filters.
- MD (medium duty): Suitable for medium contamination levels, such as those typical in urban settings. MD filters offer a service life 4 times longer than LD (light duty) filters.
- LD (light duty): Considered an entry-level solution for low concentrations of contamination or occasional contamination events such as forest fires or fog.
- vLD (very light duty): Suitable for environments with minimal performance demands. They represent an entry-level class at 50 percent of LD filter capacity.
The test outcome for a particular filter is represented in a standard and consistent format, for example 'Toluene MD 90'. In this instance, the test result begins with the name of the test gas (e,g. toluene), followed by a performance class designation (MD), and concludes with the measured average efficiency (90 percent). This value clearly illustrates the filter's effectiveness in consistently exceeding the threshold of the designated performance class throughout its operational lifespan.
Applying the new ISO 10121-3 standard ensures greater transparency and empowers customers to make informed decisions based on clearly defined ISO standards. The advantages are straightforward: better filtration efficiency leads to improved protection, lowering regular operating expenses and reducing maintenance costs.
MANN+HUMMEL provides an extensive selection of molecular filters specially tailored for a diverse array (wide range) of applications. We gladly assist you to identify the matching filter solution for your needs to ensure clean air in your facility. Feel free to contact us here.