KANBrief 1/09
In order to prevent unnecessary exposure of employees and other persons present at the workplace to hazardous substances, manufacturers are obliged to reduce the emissions from their machines at their origin if at all possible. This requirement is not always adequately observed on concrete smoothing machines, with the result that they frequently emit large quantities of harmful gases. EN 12649:2008, the standard governing these machines, urgently requires improvement in this respect.
Concrete-floor layers work on concrete smoothing machines, frequently for the duration of a full shift, in residential and industrial construction. Accidents caused by carbon monoxide poisoning during this work prompted the German OSH lobby to address the underlying causes.
The BG responsible for the construction sector and the regional authority for consumer protection in Dessau conducted measurements showing that where petrol-engined concrete smoothing machines without catalytic converters are used in indoor areas, the concentration of carbon monoxide may be several times the workplace exposure limit values. The limit values may even be exceeded outdoors.
Petrol-engined concrete smoothing machines with and without catalytic converters are frequently used on the same construction site. During measurements of the CO concentrations at the operator of a concrete smoothing machine with catalytic converter or of another lowemission machine, it was found that the enormous CO emissions of the smoothing machines without catalytic converters may influence the entire working area. In other words, employees operating a machine with a catalytic converter are also affected. Irrespective of the number of petrol-engined smoothing machines employed and the size of the rooms or halls, the workplace exposure limit value of 35 mg/m3 stated in the TRGS 900 technical rule governing hazardous substances may be assumed to be exceeded substantially and frequently. This even applies to very large halls (in some cases the size of several football pitches) with open sides. Both the workplace exposure limit value and the shortterm exposure limit value were substantially exceeded during the measurements performed.
Inadequate requirements in the standard
EN 12649:2008 “Concrete compactors and smoothing machines - Safety“, which has just been completed, addresses the hazard presented by the inhalation of harmful gases from internal-combustion engines. For concrete smoothing machines, however, the standard‘s sole requirement in this respect is that the gases be routed directly away from the operator‘s face. In addition, such machines should be connected to a gas evacuation system when operated in enclosed spaces. At present, petrol-engined smoothing machines are being placed on the market in full compliance with these inadequate standard provisions with the instruction that they may not be used in enclosed areas, or that the operator is responsible for evacuation of the exhaust gases. Since indoor areas constitute an essential area of application, however, and the use of hoses for the discharge of exhaust gases is not generally practical, misuse of these devices is foreseeable, and is also witnessed in practice on construction sites, with the consequences described above.
The provisions of the standard do not correspond to the safety level required by the Machinery Directive. Petrol-engined concrete smoothing machines with catalytic converters or gas-powered devices with substantially lower carbon monoxide emissions have already been on the market for some time.
For these reasons, KAN has asked the German Federal Government to submit a formal objection to the standard to the European Commission. The Machinery committee of the European Commission, which holds technical responsibility, has now sustained the objection. The presumption of conformity to which EN 12649 gives rise will consequently be subject to a restriction in future with regard to this particular hazard. A warning to all stakeholders concerning EN 12649 will be published in the Official Journal of the EU stating that for all smoothing machines placed on the market for the first time, a better solution is required to the problem of carbon monoxide emissions than that currently set out in the standard.
The European Commission can also be expected to issue a mandate calling upon CEN to present a suitable amendment to the standard. This decision has no direct effect upon the use of devices already placed upon the market, however. Where such devices are concerned, measures can be taken only on the basis of the provisions governing the health and safety of workers at work.
Corado Mattiuzzo
mattiuzzo@kan.de