TNO Worst Case Room

TheLaboratory for Materials, Energy and Construction (MEC-Lab) at TNO in Delft incorporates a climate-controlled unit rather ominously named the “Worst Case Room”. This is specially equipped to study the dust emissions produced by professional tools, especially those of fine particulate matter (PM).



To create “worst case” conditions, the test environment mimics an enclosed workplace on a construction site, such as a bathroom or hall, with limited ventilation and a source of relatively high emissions. In this setting, the tool being tested is operated continuously for one hour. Also present are..


  • A dust extraction unit.
  • A vacuum extractor or other specific dust control device.
  • Building materials.
  • The operator.
  • Measuring equipment.

The Worst Case Room has been designed specifically for the evaluation of innovations and to test and validate tool systems for compliance with current Workplace Exposure Limits (WELs).


The room’s basic specifications are...


  • Dimensions: 2.5 x 2.5 x 2.3 m.
  • Volume: 15 m³.
  • Ventilation input: 10-250 m³/h (adjustable).
  • Temperature: 10-40°C (adjustable).
  • Humidity: 20-95% (adjustable).

For tests on hand and power tools, the following settings are made. 


  • Ventilation input: 150 m³/h.
  • Temperature: 20°C.
  • Relative humidity: 50%.

 Dust levels are measured at three sampling points.


  • In the inhalation zone immediately above the operator’s left lapel.
  • In the inhalation zone immediately in front of the operator’s mouth.
  • In the inhalation zone immediately above the operator’s right lapel.

Respirable crystalline silica (RCS) is sampled using FSP10 cyclones with a flow rate of 10 dm³/min. and 37 mm glass microfiber filters. For hardwood dust, PAS sampling heads with a flow rate of 10 dm³/min. and 25 mm glass microfiber filters are used.


The measurement protocol can be downloaded here.

Artist’s impression of the TNO Worst Case Room.


Artist’s impression of the TNO Worst Case Room.

EPTA Test Room

EPTA, the European Power Tool Association, has a similar test facility at the Hilti plant in Germany. That has a volume of 200 m³ with minimal ventilation (no mechanical input or extraction). The other test conditions (source, tool, extractor, etc.) are the same as those at TNO, and the measurement and analysis methods used are also either identical or very similar.


Nonetheless, the differences in volume and ventilation produce different test results. Those obtained at TNO vary from EPTA findings by as much as a factor of two. More fundamental research is needed in order to arrive at a common European test protocol.


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