Division I Gravimetric method

The method selected shall be a gravimetric method which is capable of measuring the total quantities of dust emitted through the discharge ducts.

Account shall be taken of the concentration of asbestos in dust. When concentration measurements are required, the concentration of asbestos in dust shall be measured or evaluated. The controlling authority shall decide on the periodicity of such measure, according to the characteristics of the plant and of its production, but this should be initially at least every six months. If a Member State has established that the concentration does not display any significant variation, the frequency of measurement may be reduced. Where periodical measures are not taken, the limit value specified in Article 4 of the Directive applies to the total dust emissions.

Sampling shall be conducted before any dilution of the flow to be measured.

The sampling must be conducted to a precision of ± 40 % and an accuracy of ± 20 % at the limit value. The limit of detection must be 20 %. At least two measurements under the same conditions shall be made in order to check the compliance with the limit value.

Operation of the installation

Measurements shall only be valid if sampling takes place while the installation is operating normally.

Selecting the sampling point

Sampling shall take place at a point where there is a laminar flow of air. As far as possible, care shall be taken to avoid turbulence, and obstacles which might disrupt the flow of air.

Modifications required for sampling

Suitable apertures shall be made in ducts where sampling is to take place and proper platforms shall be provided.

Measurements to be taken before sampling

Before sampling commences, it is first necessary to measure air temperature and pressure and the velocity of flow in the duct. Air temperature and pressure shall normally be measured along the sampling line at normal flow rates. Under exceptional conditions, it is also necessary to measure the water vapour concentration so that the results can be amended accordingly.

General requirements of the sampling procedure

The procedure requires a sample of air from a duct carrying the emissions of asbestos dust to be drawn through a filter, and the asbestos content of the dust retained in the filter to be measured.

The sampling line shall first be checked to ensure that it is airtight and that there are no leaks which might give rise to measurement errors. The sampler head shall be carefully sealed off and the sampler pump started up. The rate of leakage shall not exceed 1 % of the normal sampling flow.

Normally sampling shall be conducted under isokinetic conditions.

Duration of sampling shall depend on the type of process being monitored and the sampling line used and the sampling period shall be sufficient to ensure that an adequate quantity of material is collected for weighing. It shall be representative of the full process being monitored.

When the sampler filter is not in the immediate proximity of the sampler head, it is essential to recover materials deposited in the sampling probe.

The sampler head and the number of points where samples must be taken shall be determined in accordance with the national standard adopted.

Nature of the sampler filter

The filter appropriate to the technique of analysis used shall be chosen. For the gravimetric method, glassfibre filters are preferable.

A minimum filtration efficiency of 99 % is required, as defined with reference to the DOP test using an aerosol with particles of 0,3 μm diameter

Weighing

An appropriate high precision balance shall be used.

In order to achieve the accuracy required for weighing it is essential to condition filters thoroughly before and after sampling.

Expression of results

In addition to measurement data, results shall record temperature, pressure and flow data and shall include all relevant information, such as a simple diagram showing the location of sampling points, the dimensions of ducts, the volumes sampled and the method of calculation used to obtain the results. These results shall be expressed at normal temperature (273 K) and pressure (101,3 kPa).