The air we breathe is becoming increasingly polluted, especially in urban environments. But improving indoor air quality is no longer just about filtering visible particles.

In reality, air contains two main categories of pollutants: particles (dust, pollen, aerosols) and molecular pollutants (gases and chemical vapors). Molecules are approximately 1,000 to 10,000 times smaller than the particles captured by HEPA filters, whose most penetrating particle size (MPPS) typically ranges from 0.1 to 0.3 micrometers (µm).

To ensure healthy indoor air, it is essential to address both types of pollution, each requiring specific filtration technologies.

ISO 10121-3:2022 standard for evaluating and classifying molecular air filters

To provide a standardized framework, ISO 10121-3:2022 allows the classification of molecular air filters within a system for GPACDs (Gas Phase Air Cleaning Devices).

This standard defines a method for evaluating and classifying molecular air filters based on their performance against a typical group of gaseous pollutants. It establishes filtration classes and capacities using the most common air pollutants (WHO) : Ozone, Nitrogen dioxide, Sulphur dioxide and Toluene.

As a result, it quantifies the selection of the most suitable molecular filtration solution based on local air quality conditions. When combined with ISO 16890, which addresses particulate matter, it enables a comprehensive approach to indoor air quality — ensuring protection against both airborne particles and harmful gases.

The molecular filter classes are divided into 3 parts : 

⋅ The reference gas (or contaminants) : O3 (Ozone), NO2 (Nitrogen dioxide), SO2 (Sulphur dioxide), C7H8 (VOC).

⋅ The capacity rating of the filter : vLD (very light duty), LD (light duty means low capacity and relatively short lifetime with rated average efficiency), MD (medium duty means four times higher capacity and lifetime compared to LD), HD (heavy duty means 16 times higher capacity and lifetime compared to LD).

⋅ The average efficiency over the filter's lifetime : The percentage of gas removed over the filter's entire life.

This filter would have a medium capacity for Ozone and would remove on average of 60% of Ozone over its lifetime

Guide to selecting the right filtration solution for particles and gas-phase polluants

Choosing a molecular air filter is not a trivial decision. It requires considering several key parameters to ensure optimal performance and suitability for your environment.

This guide walks you through 4 essential steps to help you select the right filtration solution.

Depending on your needs, you can choose between combined filtration solutions (addressing both particles and molecular pollutants simultaneously) or dedicated molecular filters designed specifically for gas-phase contaminants.

Determine your ODA 1 (G), ODA 2 (G) or ODA 3 (G) based on the air quality index.

Define the required indoor air quality for your building based on its occupancy, and hygiene requirements (SUP (G) to SUP 5 (G)).

Determine which gas has the highest exceedance percentage in your location.

Select the solution that meets the required efficiency and Life expectancy goals.

Start by identifying the level of outdoor air pollution using the Air Quality Index (AQI). This map allows you to classify your environment as ODA 1 (G), ODA 2 (G), or ODA 3 (G), from the least to the most polluted.

*ODA (G): Outdoor Gas Air Quality

*Mean values according to the 2021 WHO AQG:
NO2 – Annual average
SO2 – 24h Average
O3 – Peak season average

Next, determine the required indoor air quality based on your building's occupancy and specific requirements. The classification defines several levels from SUP 1 (G) to SUP 5 (G), ranging from standard needs to environments requiring very high air quality (hospitals...)

*ODAg: Outdoor Gas Air Quality

*Mean values according to 2021 WHO AQG:
NO2 – annual average
SO2 – 24h average
O3 – peak season average

Analyze the pollutants present in your geographical area and identify which gas has the highest exceedance percentage. This step is crucial and will guide you in selecting a solution adapted to your needs.

Finally, select the solution that meets the required efficiency and life requirements.

*Recommended
**Required

These filters are designed for environments where space is limited and both particles and light odors need to be controlled. By combining particulate filtration with carbon-treated media, they effectively capture dust while reducing gaseous contaminants.

*Our molecular products are tested according to ISO 10121

Source : Eurovent