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Molecular filtration has always been a dark art, with few companies having the experience of its successful application.

Many carbon filters have historically been specified as a tick-box exercise, but now there is an effective new standard to categorise molecular filters performance.


ISO 10121-3:2022 categorises activated carbon filters into Heavy Duty, Medium Duty, Light Duty, and Very Light Duty.


  • Light Duty (LD) filters are for OAQs with only marginal requirements for removal of gaseous pollutants
  • Medium Duty (MD) have 4 times the lifespan of LD filters
  • Heavy duty (HD) filters have 20 times the lifespan of LD filters.


ISO 10121-3:2022 represents a welcome step-change in the selection of molecular filtration in the same way the ISO16890 did for particle filtration.


Read more about our solutions for air quality remediation with molecular filtration.


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Adam Taylor