Examples of particle sizes

Particulate matter

Particles which never fall and are always in the air are smaller than 1 µm. Some bacteria are smaller than 1 µm, but the main representatives of this category are metallurgical dust and oil mist. Particles that are larger than 0.1 µm and smaller than 1 µm are covered by the filters in classes F5-F9, but the E10-U17 classes also catch these particles.

Ultrafine particles

Particles that are smaller than 0.1 µm can only be seen with a scanning electron microscope. Fine oil mist particles measure between 0.01 µm and 0.1 µm. Some tobacco smoke and asbestos particles are even smaller than 0.01 µm. Most viruses and extremely fine metallurgical dust measure between 0.001 µm and 0.1 µm. Only EPA, HEPA and ULPA filters in classes E10-U17 can filter these particles. Some of the particles that are smaller than 0.01 µm are already filtered by activated carbon.

Falling particles

Coarse particles measuring between 1 mm and 0.1 mm (= 100 µm) can still be seen with the naked eye. Examples of these include heavy industrial dust, sand, mist and fibres. Smaller particles measuring less than 100 µm can only be seen with a microscope. Examples of these include pollen, cement dust, coal dust, coarse metallurgical dust or general falling dust particles that are larger than 1 µm.

The particle sizes correspond to filter classes G3-G4, but they are also trapped by the much finer filter classes F5-F9 and E10-U17.

Gaseous contaminants

Gas molecules and pesticides are rarely larger than 0.001 µm and  activated carbon is the only filter medium for particles this small. They are carried by the air and can penetrate as far as the pulmonary alveoli when a breath is taken.

Apart from the amount of contaminants, the particle size distribution and the operating conditions, there are other factors which can influence filter selection decisions. It is therefore essential to have professional advice and possibly an on-site assessment so that you can profit from the experience of a global company like TBH GmbH.