Classification of contaminants, and extraction and filter technology terms
Many different contaminants are released in the workplace through various processes. The following figure provides an overview of contaminant classes:
Liquids and solids can exist as aerosols, or droplets and particles so small they float in the air. These are often referred to as vapours, mists or smoke. Particles and droplets can take hours to settle and while airborne are particularly dangerous for people, machinery and the environment.
They can be distributed over a wide area and even spread their harmful effects far away from the production site.
Dust, smoke, mist or gases and vapours are released during many work processes. These sub-stances have been shown to impact work performance and health.
Possible health consequences include:
- Inflammations and tissue changes in the breathing organs
- Asthma, allergies, functional disorders of the lungs
- Deterioration of the lung’s ability to clean itself, lung cancer
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 parti-cles 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 M5-F9 and E10-U17.
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 M5-F9, but the E10-U17 classes also catch these 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 nanodust 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 ac-tivated carbon.
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.
The weight and size of a particle is of importance for its settling time. The smaller and lighter the particles, the greater the possibility that they will remain floating in the air helped by thermal currents and vortices. The following figure shows how long particles float in the air before they settle. The settling times apply for droplets or particles at a height of one metre.
Particulate matter is a health risk
The finer the particles, the greater the health risk that they pose. It is important to note that the chemical composition of fine dust is not the only decisive factor in assessing the health risk, be-cause even chemically non-toxic particles can also penetrate deep into the respiratory tract, and some particles may even reach the pulmo-nary alveoli.
Fine dust is believed to be cancer-causing, even without having an immediate toxic effect. A great load is placed on the bronchial area and lungs, if the respiratory tracts or the pulmonary alve-oli are blocked by fine dust particles. Depend-ing on the application, ultra-fine particles can impact the health of employees and even the product quality.
Harmful ultra-fine particles remain in the air that we breathe for a particularly long time
Particles with a size of 15 µm settle within one minute, unless they are moved by air currents. Settling can take longer in higher areas. The settling time is 3 minutes for particles with a diameter of 10 µm, and 8 minutes for particles with a diameter of 5 µm. Since settling times do not increase in a linear fashion, particles with a diameter of 1 µm need 4 to 5 hours to settle. Even smaller particles remain suspended and never settle. This means that ultra-fine particles which are particularly harmful to health also remain for the longest period of time in the air, where they can be inhaled.
Coarse dirt harms people and damages machinery
While fine particles remaining in the air for a particularly long time are a health hazard, coarse particles settle quickly and contaminate surfaces, machine parts and the interior of the machine (if accessible). When the air moves, the particles can be distributed over a wide area and inhaled, which places an additional burden on the respiratory tract.