Customizing Vacuums for occupational safety and prevention of health hazards

Dust can jeopardise human health if the concentration of dust per cubic metre of air is very high. However, some kinds of dust can have an extremely toxic effect even in very low concentrations, causing irritation of skin, bronchi and nasal membranes. They can also cause diseases such as asthma and cancer. Dust is very common in the industrial production processes (heavy metal dusts) and craft work (asbestos, timber or plastics, etc.). Moreover, in high concentrations certain dusts can be highly inflammable or explosive, regardless of whether it endangers health.

Dust and its implications on health

The size of particle also plays a significant role in how hazardous the dust is. Unlike coarse dust (particles with a diameter > 10 µm), fine dust (particles with a diameter < 0.1 to ≤ 10 µm) can pass through the respiratory tract into the lungs. In addition, fine and ultrafine dust absorb a high content of heavy metals such as Lead, Beryllium or Mercury, or if substances such as sulphur, nitrogen compounds or hydrocarbons accumulate in it, its harmful effect gets exacerbated.

In order to counter the dangers of dust, the first vacuum cleaners were built in the United States around 140 years ago. Now there is a vacuum for almost every application. However, to choose the right one from the extensive range on offer, one must be precisely acquainted with the kind of dust that accrues, with the statutory regulations for dealing with it & eliminating it, the classification of vacuums and filter technology.

Until a few years ago, dust hazards in workplaces were assessed on the basis of their concentration in the air. In Germany this was known as the MAK (maximum workplace concentration) value. Germany introduced a new Hazardous Substances Ordinance (GefStoffV) in 2005. It prescribed a new measuring concept known as the AGW, or workplace threshold value. In practice, this means that the lower the AGW value for dust, the greater the danger it poses to health.

Choosing the right Vacuum

In this context, vacuums are categorised mainly on the basis of filter performance. Vacuums are now divided into L, M and H categories.

L (low-risk) is dust with an AGW value > 1 mg/m³. This includes substances such as plaster, mica, lime, kaolin, molybdenum and tantalum. The filtering efficiency requirements (degree of separation) for these vacuums are, therefore, very straightforward, with maximum permitted permeability to dust of one per cent. There are no regulations governing the disposal of L dust, so L vacuums are popular with tradesmen who need to clean up dirt. However, they would be well advised to use a vacuum in the higher, M, class. Above all, M class vacuums hold back fine dust that can enter the lungs and trigger allergies.

The degree of separation of filters in M (medium risk) category vacuums is geared to dust with an AGW value of > 0.1mg/m³. The maximum permitted permeability is < 0.1%. M dust consists of copper, platinum, nickel, borax, manganese and timber. The main target groups for these vacuums are therefore building and timber trades, the automotive sector, the restoration business and areas of the chemicals and pharmaceuticals industries. Since the dust has to be removed from the vacuum and disposed of without stirring up dust, M vacuums have a paper filter bag with a sliding seal and disposal bag. They also have a flat pleated paper filter for cleaning the vacuum’s exhaust emissions. If the machine is used for vacuuming up wet or abrasive matter, a flat pleated filter made of polyester fleece is fitted.

All dust with AGW values of < 0.1 mg/m³ is classified as dust class H (high-risk). The filter efficiency requirements for these vacuums are very stringent, with a maximum permeability of < 0.005%. The H group includes substances that are hazardous for health and pathogenic, such as Beryllium, Lead, Cadmium, Cobalt and Asbestos. It also includes dust that is contaminated with bacteria, mould and viruses. H class (and M class) vacuums are therefore called safety vacuums. They are mainly used by roofers, building and installation trades, and in the electrical, pharmaceutical, chemical, metal and plastics industries.

In this category, the dust collected must be disposed of without allowing any dust to escape. H vacuums are therefore equipped with a safety filter sack and a Class H main filter. The safety filter sack retains the dust. To ensure a dust-free filter change, it has a plastic sleeve that is slipped over the sack and sealed.

The H filter is usually a flat pleated filter that also cleans the exhaust. Its filtering medium consists of fibreglass mats with a fibre diameter of approximately 1 to 10 µm. So that it can be changed safely the H filter is in a frame, together with which it is disposed in a plastic bag as required by law.

In the past, Asbestos was considered to be a general building material with many positive properties, such as good heat insulation, good fire safety properties and a very good friction coefficient that made it especially useful for vehicle brake linings. We now know that asbestos dust is extremely dangerous because its fibres easily enter the lungs, where they can become embedded in tissue and cause lung cancer.

As far as possible, Asbestos should be vacuumed up directly in the place where it originates. Only Class H vacuums can be considered for this work. Furthermore, they are licensed to vacuum asbestos. Machines of this kind can be identified by the H classification.

Precautionary measures and regulations

Explosive substances must also be disposed of safely. This presupposes, first, a precise knowledge of the properties of fine-particle dust such as powder, flour, wood or metal dust. The more that is known about its combustibility and explosive behaviour, the more meaningful and purposeful the protective measures that can be taken. They include vacuuming up combustible dusts (except for dust with an extremely low minimum ignition power of ME < 1mJ). Only vacuums that comply with what is known as the ATEX Directive (94/9 EC of 2003) may be used for this. This Directive sets out inter alia the requirements for the characteristics of appliances for use in areas where there is a risk of explosion. It distinguishes between gas-ex and dust-ex areas, and categorises the equipment to be used for each.

Even machines with dust-ex protection cannot be used everywhere because areas where there is a risk of explosion place different demands on vacuums, depending on the extent of the potential risk. So the ATEX Directive defines different groups of appliances and categories of risk.

Group l machines are for use in underground mines (M1 and M2: M = Mining), while Group 2 machines are approved for use in non-mining areas. Both groups are subdivided into three risk categories, “very high,” (1), “high,” (2) and “normal.” (3). The ATEX requirements for vacuums are defined in line with these groups and risk categories.

Risk categories 1 and 2 (dust-ex areas of Zones 20 and 21) are usually permanently installed vacuum devices.

Mobile vacuums come into risk category 3. They may be used in dust-ex areas in Zone 22, where a dusty atmosphere capable of exploding occurs only rarely and for a short time (inter alia mills, warehouses, the pharmaceuticals industry, the chemical industry, the food industry, the electrical industry and the paper and powder processing industry). Since explosive dust in Zone 22 areas may also develop a toxic effect, the requirements for the filter efficiency of vacuums are the same as for dust classes M and H.

Machines approved for Zone 22 are identifiable by their B1 labelling according to DIN EN 60335-2-69 Annex AA. These machines have at least classification B1M or B1H and have been designed and built in accordance with protection class IP 54 (DIN 40050). In order to neutralise dangerous and explosive dusts, in some of these vacuums the hazardous substance vacuumed up is drawn through a water bath, whereas water-reactive substances must be vacuumed up and filtered dry. Some vacuums can now do both.

Challenge and solution

Choosing an appropriate vacuum is not an easy task. Essentially, the choice always depends on the risk assessment. The vacuum manufacturer should give good advice as a matter of course, drawing attention to technical details of the machine. Nowadays, a good vacuum has an effective filter cleaning system that shakes the filter out automatically, filter bags that are easy to use and can be disposed without allowing dust to escape, and locks that prevent erroneous operation of the vacuum. Users who pay attention to the operating instructions will always achieve the best possible cleaning result.

Dr Marcel Schoch

Freelance Journalist