Round-robin test for solvents

• Production of sampling tubes
  
  The production of samples for organic solvents is conducted by an external laboratory.
  
  The loading of the sampling tubes is done using a dynamic test gas apparatus. The apparatus is displayed in the figure. Only one sampling tube is loaded. The pump used to load the collecting test tubes has to be calibrated. The volume drawn through the test tube is measured for constant flow pumps with a gas meter during the sampling procedure.
  
  If a discontinuous (reciprocating) pump is used, the volume of a single stroke is determined before the procedure is carried out. During sampling, a suitable counting apparatus records the total number of strokes so that multiplying the total number of strokes with the single stroke volume yields the total volume.
  
  After the sampling tube is loaded, it is closed with its polyethylene cap and can be supplied to the analysis.
  
  
• Assignment of the sampling tubes
  
  Charcoal tubes of the B and NIOSH types, made by the company Dräger, are used. Which of the two test tubes is selected is up to the participating laboratory. The absolute assignment relates to the MAK or TRK value of the respective harmful substance (see Table).
  
  The following marginal conditions are assumed for the calculation:

1. Range of concentration: 0.01 times to 2 times the maximum workplace concentration (MAK value) or technical exposure limit (TRK value)
2. Volume flow:
   for TYPE B - test tube: 20 l/h
   for NIOSH - test tube: 8 l/h
3. Duration of sampling: two hours

A test set consists of:

• • a packet of unopened test tubes from the same production batch
  • three sample test tubes with each three to five solvents to be determined of differing concentrations, see Table.

Participants are informed of which samples contain chlorinated hydrocarbons. The loads will lie in the ranges listed in the table for the 17 substances.