WATSIN – An Algorithm That Predicts Workers’ Exposure to Dusts and Chemicals

WATSIN is a web-based algorithm that predicts worker exposure to dusts and chemicals. Answer 6 questions about the nature of the process and WATSIN will predict the exposure within bands. WATSIN was developed over a period of years and back-checked against actual sampling data of measured worker exposures. WATSIN has been demonstrated to be more reliable than professional judgement because it uses science to predict potential worker exposure.

WATSIN was developed by Safety in Numbers and back-checked against hundreds of sampling results provided by Winnipeg Air Testing, an industrial hygiene consulting company that does hundreds of industrial hygiene surveys each year.  A portion of the testing used to test and validate WATSIN was funded by the Research and Workplace Innovation Program (RWIP) of the Workers Compensation Board of Manitoba.  The RWIP Project Advisory Committee includes representatives from The Workplace Safety and Health Branch, WorkSafe Manitoba, Winnipeg Air Testing and Made Safe.


WATSIN takes into account factors such as the duration of use, worker position, volatility of the chemical, ventilation controls, respiratory protection, etc. and combines them into an algorithm that weighs the data entered and provides a prediction of worker exposure. WATSIN has the following uses:

  • Predict what processes in your workplace need to be sampled.
  • Estimate the level of worker exposure from a process relative to the occupational exposure limit.
  • Investigate substitution by having a prediction to see if the newer chemical will have a lower exposure
  • Determine what controls may be necessary when introducing a new product or new process
  • Estimate past exposures from processes that are no longer in place

To access WATSIN, login to the site and go to the CALCULATORS page (see the yellow box on the right).  There are two versions of WATSIN: one for dusts (welding, grinding, sanding, metal working fluids) and one for liquids (painting, solvents, etc).