High-purity quartz (SiO2) microfibre filters (2.2 µm) are used for air sampling in acidic gases, stacks, flues and aerosols, particularly at high temperatures up to 500 °C and in PM-10 testing. Because of the low level of alkaline earth metals, artifact´ products of sulfates and nitrates (from SO2 and NO2) are virtually eliminated. QM-A, sequentially numbered acc. to EPA standards, is suitable for most applications. High-purity quartz (SiO2) microfibre filters (2.2 µm) are used for air sampling in acidic gases, stacks, flues and aerosols, particularly at high temperatures up to 500 °C and in PM-10 testing. Because of the low level of alkaline earth metals, artifact´ products of sulfates and nitrates (from SO2 and NO2) are virtually eliminated. QM-A, sequentially numbered acc. to EPA standards, is suitable for most applications.