National Physical Laboratory

Automated Filter Weighing and Conditioning Service

For Ambient Particulate Mass Concentration Measurements

European standards for the gravimetric determination of PM10 (EN 12341) and PM2.5 (EN 14907) concentrations have rigorous requirements for both filter conditioning and weighing. These standards will be tightened up when the standard is revised. The allowed conditioning humidity will change from 50%Rh ± %Rh to 47.5%Rh ± 2.5%Rh. Incorrectly conditioned or weighed filters compromise validity and increase measurement uncertainty.

NPL has a filter handling, conditioning and weighing system which automates the process from start to finish. This offers the advantages of tighter environmental control for filter conditioning, improved weighing accuracy and repeatability and greatly increased throughput and reliability.

System Specifications

Climate control
Relative humidity control 35%Rh to 70%Rh
Relative humidity stability ±0.3%Rh at 35%Rh
±0.2%Rh at 50%Rh
±0.4%Rh at 70%Rh
Temperature control 18 ºC to 22 ºC
Temperature stability ±0.15 ºC
Filter Weighing
Repeatability on weights ±0.6µg
Repeatability on filters ±1.0µg
Effect of static <1.0 µg
Daily throughput 200 filters
Max filters per batch 450
Filter sizes 47 mm and 37 mm diameter


Download our flyer for more information on our Automated Filter Weighing and Conditioning Service Adobe Acrobat PDF file


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Customer enquiry line: 020 8943 8681

Last Updated: 29 Jun 2015
Created: 5 Nov 2013


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