From dust to dust
August 1st 2004 A legal responsibility lies on those responsible for cleaning up dusts in industry to ensure that it is done without affecting the health and safety of workers. The legal situation is complex for employers and cleaning companies and this article is aimed at providing better understanding of the legal requirements and the solutions available.
Industry deals with an ever-increasing variety of materials. Some of these materials in dust form are known to be hazardous to health, other materials may not be thought of as a health hazard but could, in the right circumstances, prove lethal if cleaned up using the wrong equipment. So where do we start with a hazardous dust? 1.How dangerous is it? 2. How can it be cleaned up safely? 3. What type of machine is needed?
There are dangers to health from breathing in dusts and this is common knowledge. Even flour dust can constitute a real risk to health and is a known cause of occupational asthma given prolonged exposure. The HSE publish the danger of dusts in their document EH40 (www.hsebooks.co.uk). EH40 lists the Occupational Exposure Limits (OEL) for use with COSHH Regulations.
So what exactly is an Occupational Exposure Limit?
This is the maximum concentration of the dust allowed in the working atmosphere averaged out over the length of a working day. A dust with a high OEL is safer than one with a low OEL. If the OEL is exceeded then the health of the worker is threatened and the employer may well be in breach of the law if not complying with the current EH40 requirement.
How can we clean these materials up safely?
The cleaning process must be designed so that the OEL of the dust is not exceeded. So use of brushing which may cause increased quantities of airborne dust may not therefore be appropriate. Vacuum cleaners used to clean up hazardous dust must be designed so as not to increase the dust level beyond the OEL.
Any vacuum cleaner discharges a certain percentage of the dust through the filter and back out into the working atmosphere. In the case of hazardous dusts the exhaust from the vacuum cleaner must be strictly controlled by filtration systems and machine design.
How to choose a vacuum cleaner for dust with an OEL?
The European Standard EN60335-2-69 sets the constructional requirements for a safety vacuum cleaner in order to keep within the OEL of the dust when cleaning. The vacuum cleaner must therefore be an approved safety vacuum cleaner complying with this European Standard and having an appropriate level of filtration according to the OEL of the dust concerned. (Its certificate of conformity will state that it meets the relevant European standards.)
There are 3 types of Safety Vacuum Cleaner to choose from for dusts with an OEL: - Type L with a minimum 99% filtration; Type M with a minimum 99.9% filtration; Type H with a minimum 99.995% filtration
The OEL of the dust indicates the danger of the dust and so the complete range of OELs are simply divided into 3 safety vacuum cleaner bands as follows: 1. For lower risk dusts with an OEL above 1mg per cubic metre use TYPE L machines. 2. For medium risk dusts with an OEL above 0.1mg per cubic metre but less than 1mg per cubic metre use TYPE M machines. 3. For high risk dusts with an OEL less than 0.1mg per cubic metre use TYPE H machines. Safety Vacuum Cleaners conforming to EN60335-2-69 are clearly marked as either, L, M or H.
The correct selection of such a machine for a hazardous dust means that the employer can safely assume that the vacuum cleaner will not in itself have a dust content in the exhaust which will be of danger to the worker. However the vacuum cleaner must be a certified safety vacuum cleaner under EN 60335-2-69 and not merely a standard vacuum cleaner with a special filter fitted (There are many other constructional requirements within the Standard). Following this simple process means that the hazardous dust will be cleaned up safely and in compliance with the strict limitations of the law. However the process does not end there! What if the dust is combustible?
Many dusts like flour, aluminium, titanium, tantalum, fine sugars, starch, whey powder, chocolate powder etc. are known to have explosive risks. If the dust is combustible and drawn into a vacuum cleaner then it is mixed with large amounts of air which form a cloud of dust inside the machine. All that is then required to produce an explosion is an ignition source. Vacuum cleaners produce static electricity as the dust passes through the machine. Conventional vacuum cleaner motors also produce sparks from carbon brushes. Therefore the combination of all 3 essential elements required for an explosion can be present! Fortunately these risks have been recognised and solutions found that remove the risk of ignition. Machines for combustible dusts are constructed in such a way that static electricity is safely routed to earth and the motors used do not create sparks.
The employer has legal duties under the ATEX 137 Directive to conduct a risk assessment on his processes and to then select ATEX approved equipment for use in high risk areas. The employer also has duties under the Dangerous Substances and Explosive Atmospheres Regulations 2002 that specifically include implementing control measures and providing equipment that reduce the quantity of dangerous dusts and prevent explosive atmospheres. Manufacturers of safety vacuums therefore, have produced safety vacuum cleaners that are designed for the collection of combustible dusts. Only special Notified Bodies to which the machines are submitted for testing give the ATEX certification for equipment in potentially explosive atmospheres. The ATEX approval will be specific to the category of equipment and nature of the risk (combustible gas, vapour or dust etc) considering the particular hazardous zone etc. (e.g. zone 21, zone 22, zone 1 or zone 2.)
However even if the vacuum cleaner is not working within a hazardous zone the reader is advised to consider carefully the risk involved in collecting a combustible dust with a vacuum cleaner. This is because the combustible dust and air mixture inside the container of the vacuum could explode if ignited by either a static spark or a spark from the motor of the machine. The cleaning process with a vacuum cleaner then becomes a risk that the employer should consider under DSEAR as there is an explosive atmosphere within the vacuum cleaner itself. The safe solution is to use an ATEX approved safety vacuum
cleaner in these circumstances too. More articles from Nilfisk-ALTO: | 
