Eurovent 4/26- Selecting the right molecular filter for supply air for general ventilation

Indoor air quality (IAQ) must be considered  in a holistic way assessing both gaseous and particulate pollutants. We spend about 90% of our lives indoors making clean indoor air crucial for our health. Gas-phase pollutants like ozone (O₃), nitrogen dioxide (NO₂),  sulfur dioxide (SO₂) and volatile organic compounds (VOCs) can have signification health impacts. While particulate filters capture aerosols, molecular filters are essential for removing gaseous pollutants through adsorption. Outdoor gaseous pollutants mostly come from sources of combustions meaning effective molecular filtration is crucial in urban and industrial areas for mitigating risks associated with long-term exposure to airborne contaminants for building occupants.

In 2021 the WHO adjusted its exposure levels for some critical molecular contaminants. These new thresholds enabled the Eurovent 4/26 standard to identify 3 different outdoor air conditions that can be summarised in the below table.

The ISO 10121-3 classification system provides filter rating based on capacity and efficiency against common pollutants, making selection easier for HVAC professionals. This classification simplifies the filter selection process by categorising filters based on their removal efficiency for contaminants such as O₃, NO₂, SO₂ and VOCs. By using this classification professionals can make informed decisions when selecting filters, ensuring that they meet the specific air quality requirements of their application. Appropriate classification not only enhances indoor air quality but also extends the operational lifetime of the filters, reducing maintenance cost and improving overall system efficiency. 

Selecting the right molecular filter requires a comprehensive understanding of the local outdoor air quality, building usage and filtration requirements. HVAC professionals must consider factors such as pollutant concentrations, airflow rates and system design to ensure optimal performance. The World Health Organisation (WHO) air quality guidelines serve as a benchmark for defining acceptable pollutant levels, providing valuable insights into necessary filtration efficiencies. By choosing the appropriate molecular filters based on these guidelines, HVAC professionals can enhance air quality in buildings, ensuring compliance with health standards while optimising energy consumption and operational efficiency. Regular monitoring and maintenance of filters is also crucial for maintaining filter effectiveness over time. 

Once your outdoor air environment is calculated and the purpose of your building is determined, the Eurovent 4/26 standard helps to outline the minimum filtration efficiencies of your molecular filter.