ISO 10121-3: The first ever classification system for molecular filters in ventilation systems

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. 

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.

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.

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.

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.